Vitamin B12: how much, how often?

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 $2/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.

Image credit: kokopinto / Flickr

  • Michael Greger M.D.

    A full list of my latest recommendations for optimum nutrition can be found at:

  • MsAdventuress

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

  • JJ

    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.

  • JJ

    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.

  • JJ

    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.

  • pc

    Why is it that B12 vitamins are sublingual? Is the absorption better that way/how does it work? Interesting site!

  • NCVegan

    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?

    • Toxins

      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.

  • GorillaFit

    @Dr. Gregor MD

    Did you see this? Is it possible that Cyanocobalamin converts to cyanide? Or is this unproven?

    This is from a guy who was a chemist at MIT

    • Michael Greger M.D.

      See my answer below. Thanks for asking!

  • GorillaFit


    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?

  • 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

    • Toxins

      Here are Dr. Greger’s current supplement recommendations.

      Vitamin b12 cannot be overdosed on, it is water soluble.
      Dr. Greger recommends a 250-500 mcg supplement a day or 2,500 to 5,000 per week. If you exceed this amount there is no danger.

  • Joanne

    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,


  • Johndaddy64

    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.

  • theslaw
  • Angelina

    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.

    • Toxins

      Vitamin b12 is water soluble, like vitamin c, and you cannot overdose on vitamin b12. Dr. Greger recommends 250 mcg per day or 2500 mcg per week. Check out the Vitamin b12 video series.

      Click the link, watch the video then hit “Next Video” to continue the series

      • Angelina

        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.

        • Toxins

          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.

          • Angelina

            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.

          • Angelina

            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

          • Toxins

            Correct, is online ordering an option for you?

        • Matthew

          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.

  • rachel

    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

  • alanjw

    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…

  • carlos iglesias

    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

  • jerrylamos

    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.

  • Scott Lipscomb

    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!

  • Tracy

    Can you tell me what is the best way to boost B12 for children, specifically 8-12 years olds? How much? How often?

  • Benoît Boucher

    As I write this comment, the article is 2 years old and the link does not lead to a B12 supplement. I was unable to find cyanocobalamin supplements at NutraBulk or other sources. I also came across an article that favors
    Methylcobalamin over cyanocobalamin

    So, do you have an update for B-12 supplement?

  • roy

    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!

  • bcomp

    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

  • Toni Pujades

    Would it be OK to add B12 dissolved pills to a soup or stew once it’s cooked (but still hot)? Thanks

  • Pj

    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.

  • Leiah

    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

  • Anthony Barbarossa

    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 =)

  • haripetrov

    This link: is not valid anymore. You can find it above: “but I’ll link to the $2/year one only because”.

  • Wade Patton

    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).

  • Rybakova Kristina

    Is it ok to take 500mcg every 3 days ?

  • henri

    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)???

  • Spiral

    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?

  • SoniTheEchidna

    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?

  • dan

    The article’s link to the B12 supplement he recommends needs updating.

  • SheriOrlo

    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!

  • Marcia Germain

    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