Is there such a thing as too much B12?

Question: Isn't taking too much B12 dangerous? I'm confused, because I've read several articles from you recommending large doses of the vitamin.

Dr. Wright’s Answer: I've been working with vitamin B12 therapy since 1973, and I can tell you that the only way you could kill yourself with this nutrient would be to fill your bathtub with it and drown.

Over two decades ago, there was some concern that metabolic breakdown of very large quantities of a certain form of B12 (called cyanocobalamin) might set excess quantities of cyanide (from the "cyano" part of "cyanocobalamin") loose into the body. This theory has never been proven, but you can avoid even the very remote possibility of such a reaction by using different forms of vitamin B12: hydroxocobalamin or methylcobalamin. Both are just as effective -- if not more so -- than cyanocobalamin.

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About the author


Jonathan V. Wright, M.D. has degrees from both Harvard University (cum laude) and the University of Michigan. More than any other doctor, he practically invented the modern science of applied nutritional biochemistry and he has advanced nutritional medicine for nearly three decades.

As of today, Dr. Wright has received over 35,000 patient visits at his now-famous Tahoma Clinic in Washington State.

To learn more about Dr. Wright, and to sign up for his free Health e-Tips eLetter, please visit


Anonymous's picture


Can B12 cause leukimia symptoms? My sister has been getting B12 shots for years and a few months ago was diagnosed with leukimia symptoms. A holistic medical practitioner told her this could have been caused by B12. Her alternative MD has since taken her off and I believe this is helping.

Anonymous's picture


i heard that b12 thickens the blood or creates more blood i am a woman with 16 hemoglobin will this make it worse how do i lower my 16 hemoglobin should iuse blood thiners

Anonymous's picture

Miriam Jones

I have told my daughter and other people many times that anything to excess is a poison. In other words, go for moderation on anything, even a good thing.

sirajul's picture

Mr. Sirajul Islam

Scientists have known for decades that nearly 80 percent of asthmatic children share one glaring nutritional problem. We can relieve wheezing in 80 percent of asthmatic kids through the use of one vitamin. I think, you (Dr. Wright) have found this. We shouldn’t just suffer and blame our heredity. We're probably just not getting enough of the very important foods that contain this vitamin. Lack of it creates extra pressure inside our intestines, and this also swells the veins in our legs. The remedy is so easy. The bursitis buster. Often bursitis is simply a signal that we're deficient in good old vitamin B12. By supplementing correctly the aching can go away. But we must take a form that our body can handle. Liver is the best known source. And, Sir, cobalamin concentrates, I think, are not natural, but co-natural. Would you beam some light on this?

Anonymous's picture


Anonymous@ 7/16 7:44pm: A great blood thinner is vitamin E. See a qualified naturopath for the best combination and dosage for you.

Anonymous's picture


I will always remember what my 'health Guru' mentioned years ago (Dr. Richard Schulze) concerning the cyanocobalamin form of B12, in that it is derived from sewer sludge.
For sure - both my wife and I take the methylcobalamin.

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