Doctor's Note

This is the third of a five-part video series this week on B12. For why one might choose supplements and fortified foods see yesterday's video of the day, Safest Source of B12. Tomorrow I'll cover various daily regimens. B12 is one of the few Vitamin Supplements Worth Taking. And if you're new to the issue, please see my blog post Vegan B12 Deficiency: Putting It into Perspective for some background. If you're that much of a nutrinerd to enjoy these derivations, see my nine-part video series on vitamin D starting with Vitamin D Recommendations Changed. If you'd rather just cut to the chase, see my recommendations here. As always these are just a few of the 1,500 or so topics I have videos about.

For some context, please check out my associated blog posts: What Is the Healthiest Meat? and Best Nutrition Bang for Your Buck

  • Michael Greger M.D.

    This is the third of a five-part video series this week on B12. For why one might choose supplements and fortified foods see yesterday’s video of the day, Safest Source of B12. Tomorrow I’ll cover various daily regimens. B12 is one of the few Vitamin Supplements Worth Taking. And if you’re new to the issue, please see my blog post Vegan B12 Deficiency: Putting It into Perspective for some background. If you’re that much of a nutrinerd to enjoy these derivations, see my nine-part video series on vitamin D starting with Vitamin D Recommendations Changed. If you’d rather just cut to the chase, see my recommendations here. As always these are just a few of the 1,500 or so topics I have videos about.

  • Greg Milette

    What does the equation look like for fortified soy or rice mik? How many cups a day provide sufficient b12?

    • Toxins

      Dr. Greger is recommending 250 mcg minimum of b12 per day. Silk original soy milk has approximately 1.2 mcg per cup serving.

      • BanGMOs108

        Unfermented soy products like soy milk, tofu, etc are not a safe food for anyone. It causes hormone imbalances, speeds aging, and lowers intelligence.

        Most Silk products are no longer certified organic and some are processed with hexane, a neurotoxin. And yet they can still be labeled “natural”. Some of their products may contain some organic ingredients, so the label “made with organic ingredients” is still used.

        • Massimo

          A troll paid by the milk & meat industry who cites Mercola, one of the most famous charlatans on the web, targeted even by FDA:

          • M Bel

            Wow, even a link to quack watch, brainwashing alive and well. Educate yourself a little.

    • Michael Greger M.D.

      The 250 a day is only if you take it in a single dose. Three servings a day of B12 fortified foods like soy milk should be finet. See the next video in the series for details: Daily Source of Vitamin B12

  • MacSmiley

    Please make this…. and EVERY VIDEO… EVERY DAY… visible on your YouTube homepage.

    Asking you to do this every day is getting very tedious.

    For many weeks this wasn’t a problem. So why now?

    • Toxins

      Mac, I think Dr. Greger wants people to visit the website, not youtube. Posting annoyingly everyday to a video is not a good approach to get your way.

      Furthermore, if people want to ask “Ask the doctor” type questions they can’t do so effectively on youtube, the comments are better controlled on

      • MacSmiley

        Hello Toxins,

        Thanks for your observations. Please allow me to clarify. I am not whining to “get my way”. I am asking for a reasonable accommodation.

        For the forseeable future, my only web access is an old Palm Centro which accesses YouTube videos by auto-launching the Kinoma player, but only at The player will not launch at

        I do not want to comment at (nor can I due to login issues).

        Funnelling comments to makes sense, and I believe the good doc has the option of closing off commenting at YT if he wants to.

        Thank you for your understanding.

        • Toxins

          I understand your predicament, I check the comments several times a day so if you happen to post a comment requesting a direct youtube link I can assist you with this.

        • hcdr

          you are pushing the boundaries of web accessibility :)

          • MacSmiley

            @ hcdr I know, I know. The march of web technology continues on unabated with or without me.

            @toxins Thanks for the link. There’s no substitute for my being able to access at the doc’s YouTube homepage,though, especially for a watching a series of related videos. Since Kinoma player won’t launch here, setting up a playlist is futile.

        • hcdr

          Also, youtube can take a while to update its feeds, I’ve noticed this with subscriptions I have. It’s nothing to do with Dr Greger… you just need to be patient, that’s all :)
          (or subscribe to email alerts)

  • Ted

    In the video “Vitamin B12 Recommendation Change,” dietary intakes of 4 to 7 ug dietary B12 were found to reduce the methylmalonic acid and homcysteine to desired levels. It seems to me then that “dietary intake” already accounts for the low absorption rate of B12, and hence I do not see why there is a need to up-adjust the recommended levels. Perhaps in the study the B12 was injected and that’s the reason for up-adjusting the recommended levels?

  • Meha

    How much time it takes to receptor de-saturate? I take a 2000 pill twice a week. Is iherbs a reliable brand?

    • Toxins

      It takes 6 hours for the receptors to desaturate. Stay tuned for the next 2 videos on b12.

  • Kal

    Ted beat me to my question, I suspect the good doctor made a mistake on this one.
    A plasma concentration of 200 pmol/L is typically considered sufficient and <150 pmol/L is typically considered deficient. There is a school of thought that to protect the most people the sufficient level should be raised to 400 pmol/L with under 200 pmol/L being considered morbidly deficient.
    In the Framingham Offspring Study (a source of data for some of the cited papers) it was found that people who consumed an average of 16.3±0.8 µg B12 per day, largely from suppliments, attained an average plasma B12 level of 398.1±7.8 pmol/L.
    In that study, even people who got just 4-5 µg B12 per day from food sources typically had a plasma B12 concentration nearing 300 pmol/L, a level most modern researchers would call sufficient.

    Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring Study:

    Its true, there are several mechanisms by which some people either do not absorb, can not use, or can not retain B12 well enough and thus manifest symptoms of deficiency and anyone with deficiency symptoms should be tested despite daily intake level, but for the majority it seems somewhere on the order of 16 µg B12 per day should be enough.

    As a strict vegetarian and the grandson of a pharmacist I have the habit of recompounding cyanocobalamin pills into a food ingredient so I can easily add 50 µg B12 into my food each day. There seems to be no harm to using too much B12 but I see no scientifically supported reason to alter my current practices.

    • Toxins


      Stay tuned for 2 more videos on vitamin b12 following this one.
      “Daily source of b12″
      “New vitamin b12 test”

      hopefully they answer your questions.

  • BPCveg

    Does anyone have any leads for where you get a 20 year supply of vitamin B12 for $40?

    • rhy7s

       Just another query on where to get cheap bulk b12?

  • Jessica

    Vitamin B12 is an important topic, and I’m very grateful to Dr. Greger for making this series of videos to shed light on supplementation. My question is: How much do kids need? My kiddo eats fortified foods, but probably only once a day, so I suspect we need to be supplementing weekly. What would an appropriate weekly dose look like for a child? And are there any concerns about overdoses at any age?

    Thanks so much!

    • Jessica

      I’ve done a little more reading on this topic, and found these recommendations: Do you agree that a child ages 4-8 should be taking 500 ug twice a week?

      As always, thanks!

  • Dz

    VVeeeerrryyy informative!

  • Pincopallino

    Dear Dr. Greger,
    I read on the net some statements about the negative effects of high doses of vitamin C taken together with B12. Sources are not given, or taken from general encyclopaedias. I found only one reference to a scientific study, from the ’60s in Russian in an obscure Russian journal. Do you know whether this statement is correct? If yes, do you suggest to avoid taking normal doses (below 1g) of vitamin C together with B12 supplements? Do you have any reference on this subject?
    Thank you in advance.

  • LumLum2500

    Unlike Dr. Oz, whose shows seem more like infomercials for supplements that we can’t afford if we bought everything he recommends, Dr. Greger always considers cost when discussing supplements, and I appreciate it.

  • mikeysbro

    There are several forms of b12 (like 8 to date). Thus its important to understand that cyanocobalamin and cobalamin are two different forms of b12. Cyanocobalmin is toxic 1. Nutritional yeasts commonly have this form of b12(such as red star re fortification Conversely, cobalamin found in plants can be either assimilable or not. Chorella, nori, 2 unwashed unsprayed produce 3 has the usable form while spirulina does not. Our understanding of b12 was enhanced by this study from MIT 3 a few years back which helped to solve the mystery of b12.



    Thus the cheapest source may not be the best source as its always the best choice to get our nutrition from the plants.

    • Michael Greger M.D.

      Cyanocobalamin is not only cheapest but best studied to prevent and reverse B12 deficiency safely and effectively. I’m afraid none of the plant sources you list are reliable sources. See here for a review of the available science. Thanks for leaving a comment!

      • mikeysbro

        so you are saying MIT, pubmed , etc are not reliable sources of information?

        • Michael Greger M.D.

          pubmed is just a database of articles, some useful, some less so. And the MIT source you cite does not appear to support your assertions. The paper cited in the news release you mentioned is available full-text here.

          • mikeysbro

            so what do you do with the studies like the one cited that show cyancobalamin is toxic and other studies about cobalamin in chorella, nori are bioavailable?

          • Michael Greger M.D.

            Did you read the review link I sent? One cannot rely on chemiluminescence to determine human bioactivity. I’ve addressed cyanocobalamin elsewhere. The balance of available evidence clearly shows it is the most safe, stable, and effective form of B12. Thank you for your interest in my work.

          • Massimo

            Dr. Greger,
            what do you think of this study, where the authors have found methylcobalamine (active form of B12) in spirulina?

          • Michael Greger M.D.

            Once again, your question is answered by the link I sent before.

          • Fidel Castrati

            You yourself admit that cyano-b12 is not the safest & most effective form of b12 for everyone. Common sense suggests hydroxocobalamin is superior to cyano-b12, since it has the added ability to bind cyanide which all of us can breathe in from second-hand smoke, exhaust fumes, etc. It’s so effective at binding cyanide that it’s used as an antedote in cyanide poisoning. Methylcobalamin & adenosylcobalamin also appear superior to cyanocobalamin, since they are already active and do not need to be detoxed to work for us. There are many who haven’t been able to sustain vegan eating, and maybe lack of active b12 is the reason, since most are getting their b12 as cyano-b12, either as supplements or in fortified food products. Please seriously consider altering your general recommendation on b12. Either way, thanks for all of your work!

          • mikeysbro

            I read both links but it still leaves most of my questions unanswered; namely is cyanocobalamin toxic as reported, how is it made, is mma testing sufficient for determining b12 levels, and if plant sources are deficient in b12 does it not prove that one is supposed to eat meat, and finally, if a herbivore (ie a cow) maintains adequate b12 levels where do they get it from if not from the bacteria on the plants ? Thankyou, in advance for you answers.

          • mikeysbro

            I read associated links provided (re elsewhere) and they fall short of any explanation to my questions.
            The link has not disproved aforementioned studies (re pub med) that cyanocobalamin is not toxic.
            In addition, no repudiation of the MIT study about b12 as a bacteria found on plants is the source of b12 that animals uptake but apparently humans do not for some unknown reason (though humans seem to uptake animal sources of b12 which they obtain from plants sources ..).
            The only explanation is that I cannot rely upon “chemiluminescence” to determine bioactivity . Hence the recommendation for b12 cyanocobalamin supplementation from non plant food sources (b12 is typically made from sewage).
            This only proves to me that vegans are deficient in b12 and cannot obtain it from plant sources unlike animals.
            Although I find this explanation lacking since animals obtain b12 from plant sources while apparently humans do not. Therefore are you able to address the non plant food cyanocobalamin toxicity issue and the failure of humans to uptake b12 on plants like animals can?
            You see I find it strange that animals can uptake b12 from plants though apparently humans cannot. Though there is overwhelming evidence that animal foods cause destruction of the human body’s systems that they clearly shorten human lifespan. Thus I believe that plants are the food that humans are designed to eat.
            Though this b12 issue makes no sense in that humans are unable to uptake b12 from plants. Therefore in light of the multitude of evidence that animal food causes pathological conditions to arise though humans do not uptake b12 from plant foods, this begs the question as to why humans are not getting b12 from plants.

            Personally, I theorise the the answer is three fold.
            One in that pesticides/herbicides are covering those plants preventing the bacteria from adhering to the plant or even kill them (including in the environment) .
            Two, that the artificial fertilisers etc used in modern agribusiness have destroyed/altered the microorganism environment that create the proper conditions for the bacteria to grow and thrive.(this includes water treated with chlorine, fluoride, etc)
            Three that current scientific knowledge is not sufficient to determine which form of b12 is the best form for humans to utilise including knowledge of how the human body functions as regards to b12 utilisation.

            Thus at this time there is not sufficient knowledge to understand the b12 situation properly.

      • Ravi K

        I seem to recall that the type recommended for supplementation was methylcobalamin. I am confused now. Is CyanoCobalamin better than MethylCobalamin? What is the difference between the two?Thanks.

  • BanGMOs108

    Dr. Greger. Most of the cyanocobalamin on the market is recovered from activated sewage sludge or chemically produced. How can we tell if it’s from sludge or not. In this light, methylcobalamin seems a safer choice.

    Also I would hope that you would warn people off of vegetable sourced B-12.
    It’s an analog which blocks the uptake of true B-12, the result being that the body’s need for B-12 actually increases!

    • Tom Goff

      As I understand it, the claim that most cyanocobalamin is extracted from activated sewage sludge is just an internet myth.
      If you have any credible evidence to the contrary, I’d be interested to see it. By credible I don’t mean some quack, charlatan or crackpot with a website but a professional journal etc.

      If you are a full vegetarian, you don’t eat dairy because it comes with too much baggage – transfats, saturated fats, cholesterol, hormones and antibiotics. It’s far safer to just take a B12 supplement.

  • Israel Navas Duran

    Actually your poo would be much more expensive than your pee.

  • Sílvia Melo

    Does this applies while taking a chlorella our spirulina supplement?

  • Don Perlis

    There are many conflicting reports as to the safety of high doses of B12. Some (like you) say it is perfectly safe. Others (like the Mayo Clinic) say it must be used with care in people who have dermatologic, urinary, gastrointestinal, hematological, and other issues. How can one tell who is right?

  • Eva

    Looking forward to seeing you next month in Marshal Texas

  • Gregg Stern

    What are your thoughts for those of us vegans near & over 50? More than 2,500 mcg of B12 per week? Use the Hydroxo or Methyl forms? Are you a fan of either the Hydroxo or Methyl forms over the standard Cyano form? I would appreciate your thoughts. Thanks

  • Soymoon

    I am over 50 and have a B12 absorption issue. I felt as if I had lightning bolts up and down my legs. My doctor recommended 5000mcg B12 every day. Is this over kill? It stopped the pains. Now I have a bunion that can become quite painful. Taking 10,000mcg every other day settles it down.

    Is this crazy or am I actually helping the nerve pains go away? Thanks!

  • Margasandoval65

    Dr. Greger, you must know that I love the way you teach us. If you had been one of my professors in the university, be sure, that I would never have miss one of your classes, no matter if I were in labor. Margarita Sandoval.

  • Derrek

    Where can I get b12 for $40 for 20 years. Any links?

  • Victoria

    Dear Dr. Greger,
    I’ve been vegan for the last 1.5 years and reciently got tested for B12 levels in blood. Turns out they came up pretty low, 250 pg/ml.
    I was wondering how much cianocobalamin should I take to boost B12 levels, and for how long.
    The cianocobalamin I could get comes in tablets (5 mg of cianocobalamin + vit. B6 and B1).
    Always following your amazing work.
    Thank you.

  • Dr Health Flex

    Doc ,interesting video, however cyanocobalamin has two cyanide molecules that once bound to IF are routed to the liver for methylation-conversion to methylcobalamin the bioavailable form. Synthetic B-12 is actually harmful as it is synthetic B-9 folic acid. Those who suffer with MTHFR can’t process these synthetic vitamins and those who can are robbing from the methyl groups when they have a heavy load already due to our ever increasing toxic environment. Cyanocobalamin is actually banned in some foreign countries such as the UK. I love your videos on estrogen from animals so keep
    up the good work.

  • Dr Health Flex

    As a Formulator of Transdermal nano patches I use only metylcoblamin B-12 with all my patients to bypass the hepatic pathway.

  • Natalia Nikolaevna Govyadnikov

    How to view transcripts?

  • Alexandre B

    Hi, I have read pratically all the post, but I have not find good URL for cheap B12, I mean large supply for 1 years and up. Presently I use Jamieson B12 2,500 mcg sublingual and cost me about 20$ for only 60 capsules.

    Anyone can help me to find where to buy in bulk online ?

    Thank you !

  • sara

    which web site or company should i trust for toxic free vitamin

  • Derrek

    Where can you find the $40 for 20 years? Any cheap sources you recommend?

  • veronika neukirch

    i noticed in that diagram above, the gallbladder also has a part to play in the absorption process. does one have to up the b12 dosage or frequency of taking b12 tablets, if the gallbladder has been removed?

    • veronika neukirch

      in fact what are the best ways to up absorption of b12?

    • Don Forrester MD

      This should not be a problem. The only time the dosage needs to be adjusted up is when you have problems making intrinsic factor. Pernicious Anemia is an autoimmune condition which causes the loss of gastric cells which make intrinsic factor which gives us the 1.5 part of the equation in the video. Given individual variation it is always easy enough to get your B-12 level checked with other blood work.