Doctor's Note

This concludes our five-part video series on B12 this week. Please leave any questions you may have below. If you're new to the issue, Vegan B12 Deficiency: Putting It into Perspective and Safest Source of B12 are good places to start. The consequences of B12 deficiency can be grave (see Inverted Rabbit Sign), but getting enough is easy: B12 can be taken weekly (see Cheapest Source of Vitamin B12) or daily (see Daily Source of Vitamin B12). See my full recommendations and check out the other 1000+ topics I cover here at

  • Michael Greger M.D.

    This concludes our five-part video series on B12 this week. Please leave any questions you may have below. If you’re new to the issue, Vegan B12 Deficiency: Putting It into Perspective and Safest Source of B12 are good places to start. The consequences of B12 deficiency can be grave (see Inverted Rabbit Sign), but getting enough is easy: B12 can be taken weekly (see Cheapest Source of Vitamin B12) or daily (see Daily Source of Vitamin B12). See my full recommendations and check out the other 1000+ topics I cover here at

    • JD Mumma

      In my research B12 seems to be the most confusing and unadressed  nutrient in the vegan community and is fraught with ignorance and misinformation.

      This is how I see the B12 problem:
      1) Ignore the topic as because they don’t perceive it to be an issue or at least no issue since they have no symptoms.
      Many vegans are people who spent years destroying their health – especially damaging their digestive track, decreasing intrinsic factor… and those and many other factors lower B12 creation and absorption and tend not to just magically get fixed immediately on a vegan diet.
      2) Many vegans do not eat very health vegan foods.
      3) RE: 1) do don’t get tested or tested using methods that are well known to be fairly inaccurate (e.g. blood tests)
      4) RE: 1.2.1) Try increasing with things that have either not been scientifically vetted yet to increase B12 and/or no proven scientific track record of increasing B12 levels.
      5) RE: 1.2.2) Believe they just need to eat better and don’t need to test or can skip the retesting.Comments, additions, corrections…?

      • Toxins

        There are indeed junk food vegans and healthy vegans. The issue of vitamin b12 though is fairly well addressed and this is an absolutely necessary nutrient to supplement when on a vegan diet unless one is consuming fortified foods.
        check out this video on supplements worth taking.

        • JD Mumma

          Thanks for the reply!

          Q: On a separate topic – What’s with the “Toxins” name?

  • Mark Biddy

    I just read on my bottle of B12 that it “Contains various fish species”. What’s a good all vegan source of getting B12?

  • working at it

    Question for you: My husband, who has been vegan for 4 years, has numbness in the balls of his feet. He went to his doctor, who did a blood test which indicated his B12 levels were ok. From there he went to a neurologist, where no reason for the numbness could be found. He is suggesting that he take a high dose of B12 without bothering to get a test. Thoughts?

    • JD Mumma

      What was the type of test(s) given?

    • Michael Greger M.D.

       I assume the test was as serum B12 which is insufficiency sensitive. If he doesn’t want to get a better test (like a urine MMA), I would recommend he take a B12 replenishment regimen of 2000 mcg every day for two weeks before going back to supplementing normally.

      • Rose

        Thank you for addressing this important and neglected issue. Going back to supplementing normally is risky. If the person is malabsorbing severely, and that is possible, they should stay on at least 1000 mcg dose. Your video is great, until the end. 

  • Birdy

    Hi Dr. Greger,
    I’ve viewed the videos on vitamin B-12 and have a question regarding supplementing just this one B vitamin. I read somewhere a long time ago that taking single B vitamins alone can cause imbalances in the other B vitamins. Is there anything to this?
    Thanks for which is a great resource.

    • Michael Greger M.D.

      No worries–there is no problem taking vitamin B12 in isolation.

  • Veguyan

    Raw Food World has B-12 patches available. But it’s confusing because the B-12 researcher who spoke about B-12 states that the cobalamin is not the human active form and that we need to consume the methylcobalamin form. He says the MMA score should be between .58 and 3.56. The Homocystine test should score between 2.2 and 13.2. It’s confusing because you are recommending oral cobalamin.

  • madisontm

    So, after watching a couple videos about the importance of B12, I decided to break down and buy a bottle of B12 supplements at the health foods store. But I noticed while I was there that there are also “B-Complex” supplements which contain other B-vitamins such as B1, B2, and B6. Should vegans supplement their diet with these vitamins as well or just with B12? Are all the other B’s not as important or are they like the multivitamin – leading to higher mortality rates in excess? It seems that they are not talked about as much as B12. Why is that?

    • Toxins

      A b complex vitamin is unnecessary. We can acquire more than enough of all the b vitamins through food except vitamin b12. Vitamin b12 is the only byproduct of bacteria. If you search for any plant food you can see a full vitamin and mineral profile. You will find that all plant foods not only contain all b vitamins, but they also are all complete proteins and all contain sufficient levels of omega 3.

  • Strix

      I’d like to know too! I have been taking the Methylcobalamin because I read years ago that IT was the correct one to take. :?

    Dr. Greger, am I in the danger zone?! I’ve been taking the Methylcobalamin for years now. Should I switch to the  cobalamin??

    • Rose

      If you are taking methylcobalamin, you are taking the more natural and useful form of cobalamin.

      • Strix


        That’s what I have thought because I read it years ago; however, I infer from what Dr. Greger has stated that the cyanocobalamin is the one we should be taking.

        Here (in the comments),
        he seems to saying the Methyl- isn’t the best choice. The high amount suggested looks like a typo…I  have asked for clarification; I hope Dr. Greger can clear it up for us (me!)

    • MaryAnn

      Hi everybody. I see quite a few of you have asked about which B-12 supplement is best. When I took the Plant Based Nutrition Certificate program by T. Colin Campbell via eCornell University, we had a lecture on this exact topic. The lecturer was Dr. Matt Lederman, below is what he advised based on my notes from the class:

      There are B-12 analogs – substances which are very similar to B-12. However, analogs are not biologically active in the human body, meaning they do not perform the functions that B-12 does. Examples of a supposed B-12 analogs would be Spirulina & some algae.
      Dr. Lederman advises the use of methylcobalamin, which is a natural derivitive used by the body and he advises against the use of cyancobalamin, which is a synthetic version of B-12. And that when broken down by the body to methylcobalamin and adenosylcobalamin, the process leaves a minimal amount of cyanide behind.

      • barbarabrussels

        That’s not what Dr Greger advises, he says the cyanocobalamin is the one we should be taking. See blog quote:

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

        I also read in the comments section of this video, , Dr Greger’s advice:

        “re: cyanocobalamin (the inexpensive form) vs. methylcobalamin. Vitamin B12 supplements are so cheap to produce that supplement manufacturers try to come with all sorts of fancy ways to “add value” to products so they can make more money. The coral calcium scam is the classic example–how else can you charge $20 for a bottle of chalk? Likewise, unless you’re a smoker, have kidney failure, or base your diet around cassava root, cyanocobalamin should be fine. If it’s unavailable, then I would shoot for about 2,000 mcg a day of methylcobalamin.”

        So, I guess, if you are taking the methylcobalamin form, make sure you’re taking plenty.

      • JD Mumma

        MaryAnn – Re: “B-12 analogs would be Spirulina & some algae.”
        It seems that either your notes from Dr. Matt Lederman are inaccurate or his claim is inaccurate.
        Ether way, “Spirulina & some algae” are known to HAVE (not “be”) B12 analogs, and still they can also have active B12.
        Therefore, an accurate claim would be: Spirulina & some algae are examples of some foods that contain B12 analogs.

  • PR

    Dr. Greger, there is a video in which you talk about vegan longevity vs. meat-eaters longevity. You mentioned that a study discovered that meat-eaters live as long or longer than vegans and vegans are more propense to heart attacks and neural damage due to the low levels of B12. Can you point me in the direction of the conclusion of that video? Is there a happy conclusion for vegans? How old are those findings? Thank you

  • Stephen M Albers

    Dr Greger, three of my local collection sites have not been able to locate a lab that performs the holotranscobalamin levels test. Please supply contact information for labs that can perform this test. TNX

    • JD Mumma

      Thanks you for your “sleuthing” Stephen!
      Have you been able to “find a USA source for the test.”?

  • niinest

    Thank you for the explanative video.

    I was diagnosed 17 years ago after the birth of my first child with a vitamin B deficiency after experiencing depression, brain fog and a series of other symptoms commonly experienced by breast feading mothers. After further testing the naturopath who was treating me at the time established that I was not able to assimilate the B’s orally due to IBS and made me undergo a regimen of B injections which seem to clear the matter, along with supplement of stevia for a lazy thyroid if I remember well.

    Over the years my digestive issues have gone from bad to worth and looking back at it I have most certainly experienced episodes of mild depression and the likes, though never fully paid attention to it.

    In the last 5 years I started to experience serious insomnia issues often associated with extreme bloating which led to difficult breathing only bearable in standing position. Then a little less than 2 years ago I fell pregnant with my third child, now just over a year old and whom I am still breast feading, and to the bloating was added an extreme case of restless leg syndrome, constant day and night throughout my pregnancy which in turn transformed the episodes of insomnia to a constant state as well. Aside of that the pregnancy was great and easy but I reached delivery utterly exhausted and i am presently barely recovering from the lack of sleep.

    Shortly after delivery I experienced a sharp pain in the right side of my body, my right leg having been the one most affected by the restless syndrom as well. This vanished somewhat within a few hours, though an ongoing twitchy feeling settled down after that with a constant sensation of electric current running through my nerves from my little toe, with strong sensation in the sole of my foot and incessant debilitating itching up the outer side of my legs seemingly ending in the area of my reproductive organs. I thought at first that it must be related to the slight urethrocele that seemed to occur after the delivery, but that issue seem to resolve after a couple of months and the itch remained.

    Then all at once it seems the IRS came back in force, I started to experience irritating burning sensation in my bladder and a couple of excruciating pain in my chest and back below my rib cage. Concerns for gall stones, yeast infection were raised but quickly turned down after appropriate screening test were done and came back clear.

    Other symptoms experienced which seemed unrelated to the ones above and rather common to the aftermath of pregnancy were fatigue, brain fog though rather extreme with incapicity to focus on anything, sensitivity to light and a strange sensation of seeing fleeting shadows pass by….

    That is when my gyn mentioned that i probably was experiencing a lack of vit B, which seemed to have become quite severe. She then sent me to an internist who put me on a regimen of vit B 12 complex, first orally with dosage of 15 000 mg a day for a week with no results and then shots of 5000 mg twice a week. The latter seemed to have quite positive effect and within 2 months the brain fog, sensitivity to light, fleeting shadows and inability to focus seemed to have disappeared. The nervous itch sensation though lesser at first is now slowly creeping back in :-(, along with the burning sensation and last but not least my buttocks are covered with bruises from the injection spots.

    The midwife who administrates them suggested that I get tested for the B levels to see if what they are presently at….though as I had not previously done a serum or any of the other test you mention in the video, I feel that the answer will require more than a mere testing for vit B.

    With much hope the above is clear and you’ll be able to provide with some light and advises.
    Many thanks,


    P.S.:In addition, as this will probably come to be relevant at some point, I have had to change my diet quite early on since breast feeding my little one, as I noticed that like his older brothers he seemed to develop a crying habit and some rashes around a month old. After on going an elimination diet and reintroducing the avoided food one by one, I was able to assess that wheat product would make him cry for long periods, dairy resulted in specks of blood in his stools, eggs gave him peeling off rashes and meat/fish resulted in diarrheas. So all the above were eliminated from my diet for good and he has been an easy hardly ever crying baby ever since.

  • Lin

    Try searching home blood tests for the accurate, active B12 test. Make sure injections are methylcobalamin rather than cyanocobalamin and preferably preservative free or with minimal preservatives. Dr.Greger, please could I find out whether supplements would affect the U/MMA test or homocysteine test? My body is not retaining the supplements so I’m going to buy the injections from Trim Nutrition. I would also like a test for my records. Many, many thanks.

  • DrBarbaraHoldeman

    Dr Greger, I wanted to know – is there any evidence that if a person takes a B12 supplement daily (when B12 is normal) that a person’s body could eventually not produce it’s own and become dependent on the supplement? I have heard this but have not seen any evidence of it. I would like to know if you have. Thank you so much for your work.

    • Thea

      DrBarbaraHoldeman: Dr. Greger has a great set of videos on B12. I highly recommend watching them. This is just one of the videos.

      What other NutritionFacts videos tell us is that B12 is made by bacteria in our lower gut. The B12 is so far down in our lower gut, our bodies do not absorb it properly. What is one way that we know this? People who are deficient in B12 and then eat their own poop pills (I kid you not), see their B12 levels rise.

      In other words, it’s never about how much B12 our bodies make. The issue is how we get B12 to go into our bodies. We could get it naturally say by drinking dirty water and eating non-washed fruits and veggies the way our ancestors did (or eating feces encrusted chicken the way our friends do today), OR we could take a cheap, safe supplement one a week.

      That’s a summary of the videos. Dr. Greger does a better job of explaining it. Hope that helps answer your question though.

    • JD Mumma

      You bring up a question that I believe needs to be properly addressed based on so much misinformation on this B12 topic and especially the persistent claim that – internal B12 production will be reduced from B12 supplementation!

      I understand that your question was directed to Dr Greger. I am not speaking for him, yet I thought I might provide an informative response to your question.

      My experience so far is that every person who has made such a claim has been unable (and even unwilling – mostly what seems to be delusional arrogance) to back up (they are the ones tasled with the burden-of-proof) their claim with any form of empirical medical science data. I have yet to have someone make such a claim that has had any long term formal education in nutrition/biology. Mostly the people who make such a claim (reduction of B12 from supplementation) seem to be enthusiastic diet advisers (guru’s) or from their unquestioning followers who are simply repeating their guru’s B12 statements.

      Maintaining my critical thinking and skepticism (belief and/or acceptance AFTER sufficient facts) their claim remains as a wishful hypothesis (if that) and does not yet (if ever) qualify as a medical science theory.

      My understanding of B12 in regards to the claim that, internal B12 production will be reduced from B12 supplementation (Note: the first three are my premises and #4 is my conclusion):
      1.) B12 can be made by several types of bacteria.
      2.) In order for B12 to be controlled (reduced or increased) by the human body it would require that our body control the amount and type of bacteria that produces B12.
      3.) The B12 produced in the human body is to far down the intestinal track to be absorbed sufficiently enough to raise B12 levels.
      4.) Therefore, even if our body was able to control B12 bacteria quantity and production it would not be enough to overcome the limitations of #3

      I am open to my premises and conclusion (already verifiable by medical science studies) being proven incorrect and await (without holding my breath) for their different and/or opposing evidence that is verifiable through medical science that will have the possibility of validating their claim.

      “The great enemy of the truth is very often not the lie, deliberate,
      contrived and dishonest, but the myth, persistent, persuasive and unrealistic.” John F. Kennedy

  • sunshine1

    Hi dr Greger, fantastic site

    i am on raw food, vegan, and was hoping to find some info —friends and i wonder if we can get B12 f.i. from germinated and then fermented chickpeas

    they get a ´´french cheesy´´ smell, mixed in salads quite good, if you like frech cheese that is…

    i seem to have heard ( that slightly ´´off´´ vegetables have b12 in them

    or is that myth??

    thank you

  • Ted

    Doctor, I am confused. Didn’t you say in a previous video that we can only take 250mg of b12 a day? Is taking above that only in case of cobalt deficiency?

    • Thea

      Ted: Dr. Greger’s Optimum Nutrition Recommendation page includes the following for B12:

      >> At least 2,500 mcg (µg) cyanocobalamin once each week, ideally as a chewable, sublingual, or liquid supplement *OR*
      >> at least 250 mcg daily of supplemental cyanocobalamin (you needn’t worry about taking too much) *OR*
      >> servings of B12-fortified foods three times a day, each containing at least 25% U.S. “Daily Value” on its label

      >>Those over 65 years of age should take at least 1,000 mcg (µg) cyanocobalamin every day.


      My understanding is: The reason for the non-linear amounts is because of how the body absorbs and holds B12. Now you can put this into perspective with the video information. Here is the last paragraph of the transcript:

      “If you are deficient, … one of medicine’s best-kept secrets is the efficacious use of high-dose oral B12 — safer, cheaper. 2000 microgram supplements every day for two weeks should do it, before having patients starting or resuming their regular, reliable regimen of B12.”

      I believe he is talking about deficiency in B12, not cobalt.

  • Aqua Lamb

    Dr. Greger,
    HELP. I can’t find an answer about this anywhere on the internet. Question: Was there, or is there enough B12 for us in streams, lakes, & rivers? I’m curious about what the source of our B12 had to be for the last few hundred thousand years.

    • Aqua Lamb

      And, what percent of livestock are given a B12 supplement? I’ve heard the bacteria is depleted. Shed light on the B12 rumor mill.

    • Toxins

      Aqua, it is possible. It is also possible that it was on plant foods in the wild on their surface. Humans were never strict vegans throughout human history, though. Even if we did eat some meat back in the day, we know what is healthier for us. We are not simply trying to survive (for those of us that are lucky), we have choices. It is preferable to follow the weight of evidence rather than evolutionary ideals.

      • Aqua Lamb

        Evidence is what I’m asking for. Who’s talking about evolutionary ideals?

        • Toxins

          “I’m curious about what the source of our B12 had to be for the last few hundred thousand years.” What I am saying is that this does not matter for the purposes of our health. You started with HELP, so clearly you think this is a significant issue. Hence, why I said “evolutionary ideals”.

          • Aqua Lamb

            I see you have a lot to say.
            How do I get this question around you and to the Dr?

          • Toxins

            You can email him directly, I am a moderator and am assigned to answer people’s questions and concerns.

          • JD Mumma

            “we may once have gotten all we needed by drinking out of mountain streams or well water.” Michael Greger, M.D

          • Toxins

            Thanks JD