Are there any risks of excess vitamin B12 consumption?


I have just posted some of your recent B12 videos on facebook to try and help my friends who refuse to accept the need to have an intake of B12 on a vegan diet. Most are convinced their ‘friends’ have been told by the doctors they have ‘abnormally high levels’ of B12 and have to avoid Soya milk etc. Can you advise on this? I have read there is no upper recommended limit on B12 set, and surely consuming fortified soy products wont take you to dangerous levels? I have never heard of this before. Can you advise if there are any known risks of excess consumption?

Peter /  Originally asked on Vegan B12 Deficiency: Putting it into Perspective


You cannot take too much B12 orally–your body will just pee out the excess. High serum “B12″ levels (a lousy test–see New Vitamin B12 Test) may be reflective of high levels of inactive B12 analogs (if, for example, they were eating sea vegetables). These B12 “look-alikes” are considered worse than useless and so they may in fact be at particular risk and I would urge them to start consuming B12-fortified foods or supplements with actual B12 in them. See, for example, my video Safest Source of B12 and my blog post Vegan B12 deficiency: putting it into perspective.

Image credit: Charles Haynes / Flickr

  • Tikune

    At my urging, my wife, mother and I have been vegan for seven years, during which time we’ve not been taking vitamin B12 supplements. I’m understandably concerned since seeing your videos on the risks of B12 deficiency, and I’ve spent the last week trying to “catch up” by taking 500 micrograms sublingually every 3-4 hours, approximately 3-4 times a day.

    Your statements above are clear enough, but searching for ‘B12 side effects’, the first result I find is this article – – warning of doses as high as 5-10 mg/week. At my “catch-up” run rate, I’m probably consuming 10-14 mg/week. Should I be concerned?

    Is spacing these 500 microgram doses every 3-4 hours throughout the day a good idea for someone who’s neglected the importance of vitamin B12 until now and is likely deficient? Should I get tested or just maintain these higher doses for a while?

    Thank you for the work you’re doing to educate people on how best to care for themselves and their families through nutrition. After seeing you speak at the ‘New Year New You’ event in Marshall, TX, even my “carnivorous” dad has been eating a purely plant-based diet!

  • Duke

    80-10-10 Raw Food Diet FAQ says,

    “At the same time, frozen and ice-cold foods kill the bacteria in the gut that are responsible for the production of vitamin B-12.”

    Is there any evidence for this?

    • Wade Patton

      Dunno but i did 80-10-10 a few years back and it was labor-intensive. EAT EAT EAT EAT wait five minutes and then–EAT some more. Lost a lot of weight and quickly, but the eating style did not survive my kicking of the nicotine monkey off my back. Quitting nicotine is such a miserable experience that I used every motivation and reward possible to get through it. GLAD now that the 80-10-10 was abandoned because the WFPB way of eating is much easier with less bulk consumption. Either way might be okay (and either beats the hell out of SAD), but I like this one mucho beuno.

  • alexih

    strange that you never got a response

  • Jasper

    What about other vitamins (or minerals). Are there any risks for other excessive vitamin consumption? I’m considering taking multivitamin supplements, but I don’t think I need a lot of the extra vitamins and minerals. I recently became vegetarian and I’m trying to find a way to be sure I get enough Calcium, B12, D, Omega-3.

  • carolyn

    Dr. Greger,

    I have been vegan for 19 years, and I have 4 vegan children, ages 2, 4, 6, and 8. I recently had their blood work done, and requested to have their B12 levels tested to make sure they were getting enough. Instead of their B12 levels being low, as one might suspect, all four of my children had extremely high levels – ranging from 1550-1750, when the normal range is somewhere between 200-1100. These levels are without any supplementation! The pediatricians and the doctors at the Children’s Hospital of Philadelphia are stumped, and it’s hard to find a doctor well versed in the vegan diet. All of their other blood work looked great, and they seem like perfectly healthy and happy little kids. The only information I have been able to find that seemed like maybe it could be the cause was a few brief articles stating (or in some cases only hinting) that excess consumption of high estrogen foods like soy, flaxseeds, beans, etc. could elevate B12 levels. I’m reaching out to you with the hope that you that you could shed some light on this situation for me. I appreciate all of the work that you do to keep us informed!

    Thank you.

    • Thea

      carolyn: I’m not an expert, but I have a thought for you: In one of Dr. Greger’s videos, he explained that one of the tests for B12 can produce flawed/incorrect results, showing that B12 levels are fine when in fact it is not. That test is the more common test. I strongly recommend that you watch the following video, which among other things, talks about the various tests. Maybe your kids got the inaccurate test?
      A thought for you: I think it is super awesome that you are raising your kids vegan. I may be biased, but so far, every vegan kid I have met has been super amazing, with great dispositions/calm temperaments and so smart. The thing that Dr. Greger recommends is that every vegan person, from breast feeding moms to toddlers on up do the B12 supplementation. I think (if memory serves) NutritionFacts has a video somewhere about a kid dying from the lack of B12. There are definitely videos of various people suffering permanent, horrible damage from the lack of B12. Once you see symptoms, it may be too late Why take your chances? It just isn’t something worth messing with when the insurance against the problem is so cheap and easy. Something to think about.