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Vitamin B12: how much, how often?

This week celebrates the upload of its 300th video. Though the site is officially only 9 days old, it launched “preloaded” with 288 videos taken from the last four years of my Latest in Clinical Nutrition DVD series. My primary motivation to move this body of work to the web was to make it freely available to everyone, a dream come true thanks to the Jesse & Julie Rasch Foundation. Another great benefit of this medium, though, is dialogue.

The daily new videos-of-the-day are just the beginning. The discussion begins below them in the comments section after every blog entry and video. Please feel free to ask any questions, offer any tips, make any requests, and share your experiences and expertise. So far I’ve been able to personally answer every question that’s been asked (or at least make an attempt!), and hope to keep that up as long as I can. You can also “like” the facebook page and join in on the discussion there or on our twitter page.

Tomorrow is day 10 of my 365 day marathon to upload a new video every day, seven days a week, for at least the first year. So far, of all the posts, Vegan B12 deficiency: putting it into perspective was the most commented upon. The conversation there and under the corresponding video, centered on practical questions about how someone eating vegan — no meat, dairy, or eggs — can ensure a regular, reliable source of vitamin B12. Here are the recommendations I posted:

In my professional opinion, the easiest and most inexpensive way to get one’s B12 is to take at least 2,500 mcg (µg) of cyanocobalamin once each week, ideally as a chewable, sublingual, or liquid supplement (you can’t take too much–all you get is expensive pee).

Or, if you’d rather get into the habit of taking something daily (instead of once-a-week), I recommend at least 250mcg (I know the math doesn’t “add up” but that’s due to the vagaries of the B12 receptor system — I’ll record and upload a video showing how I arrived at these recommendations).

Or, if you’d rather get it from B12-fortified foods instead of supplements, I’d suggest three servings a day, each containing at least 25% of the “Daily Value” on its label (again, I’ll explain). Such foods can be as exotic as a certain type of “nutritional yeast” or as simple as a bowl of Cheerios.

In my 20 years eating a plant-based diet, I’ve personally found the once-a-week method to be the simplest . If you share with a bunch of friends it can cost as little as $2 a year — cheaper than Cheerios! :)

I am averse to even mentioning brand names (unless I’m being critical of their products, e.g. Alli®, Applebee’s®, Airborne® supplements, Burger King®, Centrum®, Chick-fil-A®, Chili’s®, Coca-Cola®, Dow Chemical®, Eggbeaters®, Flomax®, Herbalife®, Häagen-Dazs®, Juice Plus+®, KFC®, McDonald’s®, Lipitor®, Nutrasweet®, Pop Tarts®, Purevia®, Sugar Twin®, Splenda®, Sweet and Low®, Sweet One®, TGI Friday’s®, Truvia®, Vaseline®), but I’ll link to the a few bucks a year one only because it was the cheapest I could find (please let me know if you can find a better deal and I’ll switch the link!). I certainly don’t endorse the other types of products they sell (such as fish oil, red yeast rice, spirulina, and weight loss pills). The supplement industry has a history of making misleading claims, much like the dairy industry, which I profile in today’s video-of-the-day on milk and mucus.

-Michael Greger, M.D.


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

107 responses to “Vitamin B12: how much, how often?

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  1. Congratulations! This is absolutely wonderful. Each day we get to excitedly learn a fun little snippet. I am so grateful. ♥

  2. I am your new biggest fan! I purchased volumes 1 through 5 of the DVDs and just finished watching volume 1. (I watched them in reverse order.) While I think that everyone should watch all the DVDs because all the videos together paint a big picture that is compelling, it would be difficult to get people to take the time. So, this website fills a great role.

    I have already forwarded links to various videos to several friends and family. I have two friendly suggestions for this site:

    1) Key Words
    I can tell that you have made an effort to add lots of key words, but I think the effort needs to be more complete. I’ve only done a handful of searches and two of them came up with nothing – even though I know there are videos on these topics: Searches on “xylitol” and “red rice” both turned up nothing. Since I know that the videos exist, I was persistent and found the videos other ways. However, other people doing a search may thing that the videos do not exist. So, it would be worth it to get all the key words in place.

    2) Navigation
    Suppose I do a search on ‘breast cancer’. The results return 3 pages worth of videos. Say I click to go the second page worth of videos and then click on one of those videos to watch. When I hit the back button, I would expect to be taken back to that same second page of videos on the topic of breast cancer. Instead, I get taken back to page 1 every time. The site would be greatly improved if this could be fixed.

    Hope you find those suggestions helpful.

    I have lots of enthusiasm for this information! I am a 41 year old female who has been vegetarian for 16 years, but never for health reasons. I didn’t believe that health reasons exist. I did it solely for humanitarian reasons. And knew that to be true to my humanitarian goals, I would have to become vegan.

    Last September I went to the VegFest conference in Portland. It changed my life. I finally got convinced that there really are health reasons to go not just vegetarian, but vegan. And at one of the talks, someone passed out your health recommendation sheet (or referenced it?) and that is how I found you on-line.

    I can’t thank you enough for your work. You make it painless for someone to educate themselves on real nutrition science. After seeing your videos, I have learned so much. I also have a bunch of questions and a small nit to pick, but I’ll post those under the appropriate videos.

    I don’t like to take people’s word for things. I want the science. THANK YOU for helping me to understand how to be healthy and for making it fun.

  3. I have a third suggestion for this site: The ability to edit one’s own comment. While I know I can add another comment, I’d sure like the ability to fix a spelling mistake or add a sentence to the original comment. Just a thought.

  4. I also thought I’d let you know that fingers can do the walking for us. I’m so used to typing “dot com” that several times while trying to reach this site, I typed instead of .org. I was taken to a site that looks like it is about nutrition, but it is not you. It appears that the address is already taken, but if you could buy the .com address up in the future so that both .com and .org come to here, I bet that would prevent people from going to the wrong site. Just another thought.

  5. I read somewhere that taking antibiotics can reduce the B-12 in my system. Do I need to worry about this if I am taking supplemental B-12? I am currently on antibiotics for acne. Are there any other health concerns for a vegan (or anyone) taking antibiotics long-term?

    1. Yes, there is. You will have to consistently supplement probiotics. This is very important. Antibiotics kill off all the bacteria in your gut so it is highly recommended you buy probiotics.


    In a broad sense, B12 refers to a group of cobalt -containing vitamer compounds known as cobalamins: these include cyanocobalamin (an artifact formed from using activated charcoal , which always contains trace cyanide , to purify hydroxycobalamin), hydroxocobalamin (another medicinal form, produced by bacteria), and finally, the two naturally occurring cofactor forms of B12 in the human body:

    Anyone have any imput on the subject?

  7. Hi I take the methyl lozenge form of B12 currently and it said to take 1000mcg/day, this seems like a lot. Should I really be taking that much to make sure I get what I need? Or maybe a couple times a week instead. Also do you recommend any certain suppliment brands for other things, like calcium etc, I’m weary about the extra ingredients. Thanks

      1. As a practicing physician for 20 years.. I was surprised by the most recent publication from the Journal of Clinical Oncology, which is not consistent with your answer.

        I would like to point out the most recent paper on the matter – Journal of Clinical Oncology – Vol 35, number 30, Oct 20, 2017 ;

        Men taking single source Vit B12 supplements over 55 mcg appear to have a significant increase in lung cancer risks, compared to non-supplement users in a protective trial.. suggesting that there may in fact be harm with taking too much. (The hazard ratios were impressive, with significant confidence intervals)

        Dr Gregor clearly advocates getting vitamin B in nutritional sources from his videos – and this newly identified RISK of po supplements would reinforce that message.

        The generalized belief that B vitamins are unqualified SAFE at any dose needs to be re-evaluated however!

        1. Nutritionfacts / Dr. Greger

          I’m writing to inform you of a study I would hope you would comment on:

          Brasky, T. M., et al. (2017). “Long-Term, Supplemental, One-Carbon Metabolism-Related Vitamin B Use in
          Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort.” J Clin Oncol: JCO2017727735

          The study suggests:
          Male smokers who took more than 55 micrograms (µg) of B12 each day for 10 years were
          nearly four times as likely to develop lung cancer as smokers who never took B12. As for
          those who quit smoking more than 10 years prior? They were 89 percent more likely to
          get lung cancer than those who didn’t take B12.

          I’m a former pack/day 40 year smoker. I quit in 2011 when I was 61.
          I also became Vegan at that time, started following the advice of Dr. Greger, T Colin Campbell, John McDougall, Cauldwell Esselstyn, Neal Barnard, Jeff Novick and Joel Fuhrman.
          Still am and am grateful to all of them.

          This February, a chest X-ray showed that I had a 6.7cm tumor on my right lung.
          My last chest X-ray was in 2013 and it was clear.
          In March, the upper lobe of the lung was removed.
          I’m now 68 and I have been taking 1000 µg of B12 every day, following Dr. Greger’s
          Optimum Nutrition Recommendations for those over 65.
          1000 µg is quite a bit more that 55 µg. I’ve only been a non-smoker for 7 years
          and I’ve only been taking 1000 µg of B12 for, at the most, 3 years but I can’t help but wonder if there is a connection. I doubt if anyone could say conclusively either way.
          I know if I had to choose at what caused my cancer: 1000 µg of B12 for 3 years or 40 years of smoking, I know which one I would choose.

          But I was under the impression that your body would just take the B12 that it needed and flush the rest away. My son, who is 40, was also taking 1000 µg of B12 and he said when he had his physical his doctor said his B12 was “through the roof”.

          I do know that Thomas Campbell, MD last month, May 2018, changed his B12 supplement recommendation, siting this new study.

          For now I’ve stopped taking B-12 and plan on having my B-12 checked and then supplement accordingly.
          Anyway, I’m looking forward to Dr. Greger’s opinion of this study.

            1. Having read the responses, I’m a bit concerned about taking too much B12 since a doctor cites a study on taking too much. Do you have an response? Thank you.

          1. Hi I’m a health support volunteer. I’ve actually been asked about this study once before, but not from the point of view of being a cancer patient. I’m sorry to hear about everything you are going through. We wish you all the best from all of us at

            This is just one study. And from looking at it, I cannot tell if they controlled for any other factors. For example, what are the 2 different groups eating? They could have very different diets or other risk factors. You can’t draw big conclusions from one isolated study. Dr. Greger reviews what the consensus of all the research shows. If there is substantial amount of research that begins to show a relationship between vitamin b12 and cancer, I’m sure he’ll do a video about it.

            Vitamin B12 is water soluble so that is true that your body can essentially flush away excess unlike with some fat soluble vitamins.

            If you are not comfortable taking B12 supplements and you are having your level checked regularly, I think that is fine. But certainly supplement if you become deficient.

            Dr. McDougall, who also is a champion of plant based nutrition and is very respected by Dr. Greger, takes a little more of a minimalist approach to supplements and recommends the smallest amount necessary:

            We wish you all the best.

            1. Thank you very much Nurse Kelly. Sometimes the medical establishment just throws out information that might cause fear without suggesting a compassionate solution. I am a believer in plant-based eating and a appreciate the information you and Dr. Gregor give so generously.

  8. Dr. Greger,
    Vegan, citing you as a good source, recommends DEVA (company) vitamin B 12 supplements. Their product contains methylcobalamin, NOT cyanocobalamin, which you recommend on this site and which I’ve learned contains cyanide??  So, which is it? 

    And, I thought I was getting my source of vitamin B12 from soy milk. However, I’ve heard that heating soy milk which is done in pasteurization, after the vitamin B 12 is added, can eviscerate the vitaminn B 12.

    I need some expertise here, please,


    1. Hi, -I am a nutritionist and moderator in NF team. I would recommend cyanocobalabmin form of B12. If you drink soy milk, you have to check how much and form of B12 is added to it. This vitamin do not changes with heat.

      1. why do you recommend that version? It’s hard to find pure supplements out there without a lot of harmful additives, do you have any particular brands you like?

    2. Hi Joanne, you are correct that the cyan B12 contains cyanide. I became allergic to my injections just for that reason. It was discovered through testing. I now take the methyl B12 sublingual. It is pure and no more problems or injections.


  9. I like this blog and good information.
    Golf to head stateside in 2013: Autoweek TV. Also in this episode: Nissan recruits Consumer Reports test director.

  10. On my package of vitamin B12 from Finland it’s written that 3 µg is daily dosage of B12, which is 300% of recommended daily dosage. And take no more than 1 tablet a day. Is it too small? On your site it is written: ‘I recommend at least 250mcg’ That’s strange.

      1. If the daily dosage is 250 mcg, does it mean that I must take 250/3 = about 83 pills a day??? One pill is 3 mcg, like I said. I still can’t understand :((( 4-7 mcg and 250 mcg per day are such different numbers.

        1. You need to get new b12 supplements! You can get some that are 250-500 mcg. If you choose to go your route of only 3 microgram supplements, you will have to take 3 a day 4-6 hours apart. Keep in mind, we absorb 1.5 micro grams plus 1% of the rest passively. After the initial 1.5 mcg absorption, we have to wait about 4-6 hours before we can resaturate our b12 receptors. The formula here is an example with a 500 mcg supplement.
          1.5 + .01(498.5) = 6.48 mcg, this falls into the 4-7 mcg per day range.

          It would be far less complicated to go that route, or simply take a 2500-5000 mcg dose once a week.

          1. Unfortunately, I couldn’t find any Vitamin B12 with that dosage. :( I think that is because the medical institutions in our country think that 3 micrograms is more than enough for a day (in pill form). I live in Europe, Estonia. That means I’m B12 deficient everyday :(( Maybe the soulution could be taking B12 fortified products? But they’re also not too rich in this vitamin.

          2. Ok, I didn’t read carefully. As I understand, if I take 3 pills, which contain 3 micrograms of B12, with 4-6 hour intervals, that would suffice? 1,5 x 3 = about 4,5 micrograms

        2. Absorption of B12 is poor.
          2.5ug + 1% of dosage
          2.5 + 250/100
          2.5 + 2.5
          = 5ug
          which is between the 4 to 7 recommendation.

  11. Greetings, thank you again for so many wonderful video’s and information. I just purchased B-12 energy patches
    made by .They are not inexpensive.( I have no affiliation with them at all). Mine come 8 patches to a package and they state each patch contains 0.4mcg of folic acid and 1000mcg of Methyl…B-12. Directions state using 1 or 2 patches every week–you attach one behind the ear or on the neck–, but how do you know which–1 or 2 a week?. Also, is a patch better absorbed than a pill, liquid or shot?.
    namaste’, rachel

  12. I’ve adopted a whole-food, plant-based lifestyle for health and longevity. And, in an ideal world, I’d like to be as self-reliant as possible when it comes to nutrition (i.e. grow or buy locally produced and otherwise readily available foods). This goal is relatively easy to achieve almost anywhere on the planet except maybe the extreme high latitudes (north or south) and some deserts. (I don’t plan to go to human-made stations in space or under the sea!)

    That said, I’m curious to know what would be the least amount of meat or other animal product (or bacteria-rich soil!) that I would have to eat to ensure an adequate intake of vitamin B12? And would the related health risks of consuming these non-plants seriously compromise my goal of a healthy life, free of the diseases of affluence?

    Suppose, for example, that I moved to a country or region where manufactured vitamin B12 supplements were not reliably available, and I must obtain my B12 from local sources.* If I want to stay healthy and follow my chosen way of eating, I will be obligately dependent on an external (imported), manufactured supply of non-animal vitamin B12 (and probably D3 unless I’m in the tropics).

    The natural sources of B12 I’m aware of include animal meats and bacteria that live in the soil and elsewhere on animals. If these are indeed the only sources available, then I’ll have to consume some amount of these sources -daily, weekly, monthly or at some appropriate interval- in order to stay healthy. In other words, I’d have to compromise (or give up and go back home! .

    My question then is: what is the least amount of meat or other animal product (or bacteria-rich soil!) that I would have to eat to ensure an adequate intake of vitamin B12? And would the related health risks of consuming these non-plants seriously compromise my goal of a healthy life? I’m curious to know Dr. Greger’s and others’ thoughts on this.

    * another way to frame this would be that a person just didn’t want to be dependent on the supplements industry for the rest of their life…

  13. Dr Michael Greger according to B12 vitamin , is there anyway to get the b12 from any natural source or raw food ? thank you
    kind regards

  14. For me, 78 year old vegan plus some fish and B12 pill did not work. Blood test MCV above range, Hem below range feeling poorly. A month of liquid B12 under the tongue 500 mcg daily feeling better than last 9 months.

  15. Dr. Greger,

    I was wondering if there have been any reports of any B12 supplement brands having misleading labels–i.e., not having as much B12 as they claim or even none at all. You discussed such a problem with other supplements, I think particularly herbal ones. Has this also been an issue with B12? I haven’t been supplementing (though I do eat some fortified food) but plan on starting now, due mostly to your recommendations. I would hate to buy a brand that didn’t actually have as much B12 as the label reported.

    Thanks for all the time you’ve put into all your work; it’s been extremely helpful!

  16. Hi do you think it would be a good idea to crush a 1000mcg b-12 tablet and add it to the whole wheat bread we make at home? (a homemade fortified food) Or is it better to just take sublingual ?
    Thank you for your great work!

  17. Hi.Is it better to take b12 on its own or as a B50complex twice a day or as a b100 once a day ? Is slow release good when you’re taking vitamin C later that day? thanks

  18. I take a liquid multi-vitamin with 100mcg of b12 and it says that is %1660 daily value. Is this incorrect? Do I need to be taking 150 mcg more a day? Thank you.

  19. Thank you so much for sharing your knowledge with all of us. It is your precious time and a service to human health.
    I have shared your site. It is very exciting to come and learn what is out there that we can choose to live a better life, not with pills (even so, those are beneficial,sometimes) but with the right foods. Mazel Tov

  20. Can anyone suggest an online retailer (like nutrabulk) who sells and ships internationlly a similar B12 product that was mentioned in the above article. Please & Thanks =)

  21. I’m happy with for my B12 and D3. I ordered their B12 via Amazon, and then BS emailed me and offered a free second supplement. So I ordered their D3. Haven’t done the math for costs, but this 50g bag of B12 is a few hundred years worth. Now if I could only accurately measure such miniscule doses. I’ll try my powder scale, resolution 0.1 grain (6400 micrograms).

  22. Dr. Greger hello! I have a question concerning B12. I work a lot and I have a very busy schedule during all the week sometimes with lots of pressure in the office so I take B12 by 8ml per day which consist in: B12=17.5µg, b6=6.3mg, b1=4.4mg, niacin=16mg,L-glutamin=100mg,L-lysin=10mg and L-serin=42mg.
    After the first day and the second day of use which I feel calm and I have my daily routine, in the third day I feel Sleepy and Fatigue. But i make a very good sleep and I feel very calm (especially when I have pressure, I am able to logic calmly).
    So the effect on my nervous system is managed better (I am happy with that) but Is it normal to feel tired and to be sleepy since in the afternoon?
    I can’t wait to go to bed and I make a very good sleep…I make a very calm sleep but when I wake up in the morning I feel like tired for 1-2 hours (may be because I sleep every day by only 6 hours and I have a busy daily schedule?)

    I have had exactly the same effect also when I took other B complex one year ago (but at that time may be I slept less every day by 4-5 hours)???

  23. What if I take a 1,000 microgram B12 cynocobalamin tablet orally 3 times each week? Is my taking it orally, rather than chewing it or taking it sublingually, going to leave me at risk for deficiency?

  24. I know that you get B12 in animal products. Some people have been talking about not washing plant produce etc. to obtain B12, but that is not normally possible with fruit and vegetables obtained from the greengrocer.

    I’ve been looking at a study ( and it appears that there is B12 in some non-animal sources such as dried purple laver BUT the B12 levels are not consistent.

    This source has B12 in apricots as 58.5ug/100g (,

    This source B12 in okra – from ND – 91.2ug/100g ( but it did not state if it distinguished between B12 and pseudo-B12

    Bottom line, I was wondering if there is any way that a vegan can get (enough) B12 WITHOUT having to use supplements?

  25. Dr. Greger, the link to the B12 is no longer valid. They do sell big bottles of B12, so it may just need to be updated. Thank you for all you and your staff do!

  26. Thank you so much, Dr. GREGER.
    You have changed my diet. Given me hope. Congratulations on all the great work you have done and shared.
    Amazing! Your fan, Marcia

  27. Accordingly with Dr. Edward Group III, DC, NP, DACBN, DCBCN, DABFM is the founder and CEO of Global Healing Center, cyanocobalamin is not good for you. Is it true? Is there enough scientific evidence for this assertion?

  28. Hi, i’ve been taking 5000 mcg of b12 a day for a while now. Just accidentally bought the 500 mcg dissolvable tablets instead. Is it potentially dangerous to cut back so dramatically? I would have to take so many of them to get to 5000 mcg a day…

    1. Justmakingsure, it’s not dangerous to cut back abruptly. Unless you were severely deficient 5000mcg a day was likely way more than you needed anyway. Because b12 is a water soluble vitamin you just urinate out any excess you body doesn’t use so it doesn’t harm you to take too much it just makes your urine a little more expensive. In any case you could cut back to 1000 (two 500mcg tablets) a day and most likely be just fine at least until you finish up what you just bought.

      1. Thanks for the reply, i was severely deficient when i started on it but it’s been a while and thinking maybe i can cut back now.

  29. Dr. Greger

    You recommend 250 mcg and my bottle says to take one lozenge daily but it’s 1000mcg. Is it safe to take one daily as indicated? What about for my 10 year old son?

  30. Due to Crohns disease/surgeries I don’t absorb B12. I had taken injections for 40+ yrs and now become allergic to the cobalt. I am trying sublingualB12. My doctors don’t seems to know how much to take for maintenance. So far I am doing 1000mcg of Methylcobalamin daily and chose a brand that contains only two fillers. Is 1000mcg/daily too much, too little? I don’t know. Would you give me your opinion? Thank you

  31. I want to become vegan, and I’m convinced that this is much healthier for humans, but it surprises me that if humans are supposed to not be omnivores, why do we need a supplement to give us something that is dangerous to not get enough of?

    1. Hello Victor,

      I am a volunteer moderator who helps Dr. Greger answer questions on NutritionFacts. I am a whole foods plant based dietitian nutritionist based in Scottsdale, Arizona. You ask an interesting question. I can only assume that you are thinking that the need for Vitamin B12 suggests that biologically we are “supposed” to be (genetically) eating meat?
      I don’t know a ton about cavemen, and how much meat they ate. I do remember from my biology and anatomy classes that human growth and development was evolutionarily advanced when our ancestors started sucking the marrow out of animal bones (great source of essential fatty acids). I’m not sure that this means that I should be sucking animal bones to get my EFA’s since there are many rich plant based sources of nourishment of fatty acids. With B12, Cobalamin, commonly referred to
      as vitamin B12, is the only nutrient not directly available from plants. This is because vitamin B12 is synthesized by microorganisms, bacteria, fungi, and algae,
      but not by plants or animals. Animals consume these microorganisms along with their food, which is why this vitamin can be found in their meat, organs, and
      byproducts (eggs and dairy). When we go back to our ancestral roots, we suspect that humans were not always able to eat a large source of B12 (in the occasional mastadon that was hunted and eaten) so that could explain the storage component of B12. But, since it was widely available in an unsanitized, “natural” environment, as we were eating bugs and grubs we could attain consistent amounts of B12.

      As you can see from my rambling reply, it cannot be scientifically known if humans are “supposed” to be vegan or not. Targeting one micronutritent as an argument either for or against this position is a tough sell. Instead, I can look at the myriad scientific reasons why a vegan diet offers superior health benefits in our modern world and supplement once or twice a week with sublingual B12. I prefer that approach.

      Thanks for being part of our community!

      Lisa Schmidt, MS, CN
      Mindful Benefits

      1. Thank you for your great reply. I guess it makes sense since some percent of the diet of monkeys are insects. Should the plant-based diet, if done without supplements, also consist of a bit of insects (just once a week maybe) if we only consider the health aspect and not any moral, environmental or social aspects? And if so, how much would we need to eat to get the amount of B12 we need?

        1. Okay, Victor, YUCK! You are beyond my scope of stomach comfort here. I know in some parts of the world insects are part of a normal diet, but for this squeamish girl, I prefer a squirt a week of B12 drops. You might check out Crick Nutrition for their take on the scientific benefits of eating insects. They claim “more B12 than salmon or beef!”

          This is not an endorsement of their product, rather, an invitation for those so inclined to not supplement cheaply and simply with B12 to investigate insect sources.
          Yum Yum!!

          1. “They claim “more B12 than salmon or beef!””

            Then it makes even more sense! Thank you for your help. I don’t think I will actually eat insects, it just help me rationalise a vegan diet to know that the B12 deficiency is not because eating meat is unnatural – just that we probably used to eat bugs.

            Are there any other deficiencies commonly found in vegetarians, I should know about?

   mentions a bunch: B12, creatine, “protein” – questionable since doctors never find deficiencies in protein!, carnosine, taurine, vitamin D3, heme-iron, DHA omega 3 and sulfur. I don’t really trust this supposedly very trusted site, but I want to build muscle and become stronger while having a vegan diet, and I want to be sure that I am getting what I need. Are any of these some I should worry about?

            1. Victor,

              I love Dr Greger and Nutritionfacts because it is 100% independent, existing only because of Dr Greger’s passion and donations of time and money from community members and moderators such as myself. I used to be a fan of Dr Mercola until I learned about the bias in science due to researchers competing financial interests. Dr. Greger has a great video on this you may enjoy. Dr. Mercola sells “health formulas” (eg. not food) so I wonder how this affects his information??

              In my practice as a clinical dietitian nutritionist, I have NEVER seen a case of protein malnutrition, except for severely anorexic clients (I’ve sadly had a few of those). Everybody else, not so much.

              For vegan muscle, please see He has been a competitive vegan body builder for over 25 years, and he is the son of a dairy farmer in Oregon! What a great guy. I asked Robert and two other colleagues to speak to a plant based course I teach at Arizona State University and he is amazing. Great information, highly credible experience.

              You don’t have to eat animals to get big! You might have to eat bugs, ha ha. Keep us posted!!

              Best of luck to you and thank you for being part of our community.


    2. Victor, the answer is simple. You can thank the industrial era for that. Grazing herbivores and other wild animals do not need to supplement because they eat straight from the ground and get B12 from the soil. But thanks to industrialization, the soil is contaminated with heavy metals and the like so it wouldn’t be safe for us to consume. Our ancestors didn’t have to rinse the dirt off the plants they ate. It’s also been said that the soil used to be richer in B12.

      And what’s more is that those eating meat and other animal products aren’t actually getting B12 from the animal, they too are being supplemented 2nd hand because the animals “raised” for food have to be supplemented due to the fact that they’re not out grazing and getting B12 naturally from the soil.

      When you think about things like “don’t we need meat to get…” always think of this… where do the nutrients inside the animals you might eat come from? They’re herbivorous animals so they’re getting them from plants :)

      Meat and other animal products are unnatural for humans to eat and the most detrimental thing to human health.

  32. I have learned from the reputable Dr Mcdougall that the liver can store up to 5 milligrams of B12, given than technically we only need 1microgram a day ( 3 to be super safe ) wouldn’t that mean it would take more than 3 years to become depleted ? 3 years being generous of course. He also state that B12 deficiency disease strikes one in a million.

    1. that would explain why those not supplementing aren’t keeling over. But still, given the important role of B12 and how vital it is in keeping homocysteine levels in check which are toxic to the heart and fatal when too high, I will keep supplementing once a week. But it would be awesome to see more research on all things B12, I’d love to only have to supplement once a month, or even less if possible. How cool would it be if everyone got a free B12 shot once a year… only in a vegan utopia… ok I’m done.

  33. Great question! I’ve seen various textbooks quote that we can store vitamin B12 for 1 to 5 years. Obviously, there is a bit of variation out there- but the main point is thus: we are able to store it. Hope that helps!

  34. I’m guessing it’s hopeless that you will find time to notice this request … but you said you would record a video showing the derivation of your daily B12 recommendation. Did that ever happen?

    1. Dear Laurie,

      I am not sure if that happened.

      A recent review has suggested that:

      “At present, there is no international consensus for supplementation in vegetarians. According to Carmel, a single oral dose of 50 μg, 500 μg or 1000 μg will be absorbed at an amount of 1.5 μg, 9.7 μg or 13 μg, respectively [151]. To meet the daily requirement of Cbl, one oral dose of 50–100 μg daily or 2000 μg weekly divided into two oral cyanocobalamin doses could be sufficient to meet the needs of 2.4 μg/day for healthy vegetarian adults, taking into account the efficiency of absorption and the passive route. In 1988, Herbert stated that vegetarians’ Cbl requirements could be satisfied by 1 μg tablet of vitamin B12 per day, based on human reabsorption through enterohepatic circulation [32]. This quantity is fairly low in respect to the proposed values for Cbl Dietary Reference Intake (DRI) in the general population [19,20]. Cyanocobalamin is the most economical—and historically the most used form—rendering it suitable for safe daily use [45]. There were no apparent substantial differences between the absorption of sublingual and oral forms”

      Hope this answer helps.

      1. darchiterd, does it matter what form of B12 you’re taking when it comes to the body storing it? I take methyl B12 once a week at the recommended dose above. Thanks in advance!

  35. As a practicing physician for 20 years.. I was surprised by the most recent publication from the Journal of Clinical Oncology, which is not consistent with the believe that “there is no toxic dose of B12”

    I would like to point out the most recent paper on the matter – Journal of Clinical Oncology – Vol 35, number 30, Oct 20, 2017 ;

    Men taking single source Vit B12 supplements over 55 mcg appear to have a significant increase in lung cancer risks, compared to non-supplement users in a protective trial.. suggesting that there may in fact be harm with taking too much. (The hazard ratios were impressive, with significant confidence intervals)

    Dr Gregor clearly advocates getting vitamin B in nutritional sources from his videos – and this newly identified RISK of po supplements would reinforce that message.

    The generalized belief that B vitamins are unqualified SAFE at any dose needs to be re-evaluated however!

    1. Do you have a link to the study you’re referencing? What form of B12 did they use? And what other ingredients were in the supplement? It’s so hard to find pure supplements!! Am I the only one who gets annoyed by this? It’s like seriously, we don’t need our vitamins to taste like candy…
      Anyways, It’s my very brief understanding that methyl B12 is a more natural form of B12 and this is the reason a lot of people choose this form and a lot of supplement companies use it. I’d like to hear more on the different forms, Dr. Greger doesn’t seem to mind which form its in, but hopefully a new video or article on all B12 concerns will be put on the site in the near future.

      1. this is the study:

        Also, Campbell, of nutritionstudies, took this study to start recommending taking small daily doses of B12, instead of one larger dose once a week.

        Considering your other remark that your brief understanding is that methul B12 is a more natuarl form of B12, this study appears to be very interesting:

        I would really like for Dr Greger and his team to review the newest studies on B12 and update the videos and blogs based on their findings. Even if they remain with the current information. At least I’d like to know the arguments for that.

        The B12 topic is one of the most important topics among WFPB eaters. And since this blog is from 2011, I think it deserves an update :)

        Or maybe one of the volunteers can look into these studies and comment?

        Many thanks in advance!

        1. I have been doing really well with my weekly dose of methyl B12 and someone here under another video unrelated to B12 explained the conversion process really well. Thanks for the links. I agree that the topic of B12 is very important and I would love an updated video as well addressing all concerns and also explaining the conversion and forms in more detail.

  36. I take 2,500 mcg of methylcobalamin B12 once a week, does this work the same way as taking the other kind you wrote in the article at a once a week dose?

  37. I would love to hear Dr. Greger’s opinion on this study:

    Brasky, T. M., et al. (2017). “Long-Term, Supplemental, One-Carbon Metabolism-Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort.” J Clin Oncol: JCO2017727735

    I saw it mentioned on the Colin Campbell Nutrition Studies website ( In light of the study, the author there is recommending a low daily dose of B12 via a multivitamin rather than a large-dose supplement.

    I haven’t read the study. I get the impression that the increased cancer risk for B-vitamin supplementers was confined to certain groups (male smokers yes, but not male non-smokers, and so on). But still, since Dr. Greger recommends large-dose B12 supplements, it would be great to have him weigh in.

  38. What do you have to say about the VITAL trial and data from the PROOF trial that found B12 supplementation to significantly increase the risks of lung cancer and colorectal cancer, respectively?

  39. Hi Jamie Hydro, thanks for your question. In this study they found that B6 and B12 had sex- and source-specific associations with lung cancer risk. In addition, the association in men was more pronounced in cigarette smokers. Shi et al20 reported that the genetic polymorphisms of an important enzyme involved in folate metabolism, 5,10-methylenetetrahydrofolate reductase, interacted differently between men and women with dietary vitamin B6 and B12 intakes, cigarette smoking, and lung cancer.

    Men and women have different susceptibility to tobacco-induced lung cancer and supplementation with high-dose vitamins B6 and B12 for longer duration may support more rapid cell growth and promote carcinogenesis in already mutated cells in smoking men. Because androgen signaling regulates key enzymes involved in the one-carbon metabolism pathways, the increase of androgen levels or activity in men may lead to a more profound effect.21 A study by Suzuki et al22 reported significant interaction between a polymorphism in methionine synthase reductase and smoking, resulting in synergistically increased lung cancer risk.

    The biology of the B vitamins involved in one-carbon metabolism suggests that intakes should be beneficial to cancer risk. Folate serves as a methyl donor in the process of nucleotide synthesis and methylation reactions.24 Deficiencies in these nutrients may result in greater chances of DNA damage, possibly influencing gene expression through aberrant methylation patterns, leading to initiated cells or promoting already initiated cells.24,25

    Intakes of B vitamins that meet recommended levels among those who are deficient should be useful for these reasons. On the other hand, excess supplement of folic acid and vitamin B12 was found to be associated with changes in DNA methylation of several genes that could be reactivated or deregulated during carcinogenesis.26 Like colorectal cancer, these B vitamins may have a double-edged sword effect on lung cancer by possessing dual modulatory effects that are time and dose dependent27. Most people in the United States should have sufficient intakes from diet, particularly for folate, which has been added to foods. Nonetheless, half of the US adult population uses one or more dietary supplements.16,28 Our study found that consuming high-dose individual B6 and B12 vitamin supplements over a 10-year period is associated with increased lung cancer risk, especially in male smokers. Consistent with prior evidence of harm for other vitamin supplements on lung cancer risk in smokers,29-32 the associations we observed provide evidence that high-dose B6 and B12 supplements should not be taken for lung cancer prevention and, in fact, may increase risk of this disease in men.

    So in conclusion the source, the amount and gender play a role when taking B vitamin supplementations. Dr Greger mentions if you’d rather get it from B12-fortified foods instead of supplements, I’d suggest three servings a day, each containing at least 25% of the “Daily Value” on its label

    1. It would be great if Dr Greger could respond with a more definitive recommendation on B12 supplementation for different people in light of this new research and higher risk of lung cancer for people taking high dose B12 supplements.
      Dr Kim Williams, cardiologist, was interviewed by Dr. John McDougall in a May 2019 video. Dr. Williams is recommending less than 55 mcg/day of B12 for everyone, especially for those in the higher risk category of male, over 60, and ex-smokers. But this dose is difficult to actually implement due to commercial supplements existing in such high dosages, and hard to break it down into 55 mcg portions.

  40. Hello,
    Is there a significant difference between cyanocobalamin and methylcobalamin? And which one is healthier with regards to B12 level.
    Thank you!

  41. I’ve read as much as I can in the peer reviewed literature on this and have not found any evidence of difference. There are several other forms as well…all appear to lead to the same common metabolic pathway; i.e. no difference.

  42. Hello Dr Greger,

    I want to explore the whole food plant based diet. I am worried about vitamin b12 deficiency though. Will eating a portion of meat once a week help in this regard?

    1. Hi, Jacob! You can follow a whole food plant-based diet without having to add in meat to get vitamin B12. Here is Dr. Greger’s suggestion:

      • At least 2,000 mcg (µg) cyanocobalamin once each week, ideally as a chewable, sublingual, or liquid supplement taken on an empty stomach
      o or at least 50 mcg daily of supplemental cyanocobalamin (you needn’t worry about taking too much)
      o or servings of B12-fortified foods three times a day (at each meal), each containing at least 190% of the Daily Value listed on the nutrition facts label (based on the new labeling mandated to start January 1, 2020—the target is 4.5 mcg three times a day).
      • Those over 65 years of age should take at least 1,000 mcg (µg) cyanocobalamin every day.
      • Tip: If experiencing deficiency symptoms, the best test is a urine MMA (not serum B12 level)

      See here: and here:

      For most of us, it’s probably cheaper and most convenient to just take a supplement.

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