Is a vitamin B12 shot better than taking B12 orally?

Your doctor may want you to get vitamin B12 shots, but did you know that oral B12—even for those who can’t absorb it well—has long been considered one of medicine’s best kept secrets? In fact, it’s been found that B12 supplements taken orally are just as effective as intramuscular shots in overcoming states of deficiency when you take up to 1,000 micrograms a day.

You may have heard that vitamin B12 can cause acne, but that isn’t the whole story. As first described back in the 1950s, about one in ten people erupted in acne within days or even hours of getting an injection of vitamin B12, but it disappeared rapidly when the B12 shots stopped. Certainly, those on plant-based diets have to take supplemental B12, but we don’t have to get B12 shots. Vitamin B12related acne tends to occur only in dosages in excess of 5,000 to 10,000 micrograms a week, which is well in excess of the 50 daily micrograms or single 2,000 mcg weekly dose I recommend. (Those over 65 years of age, however, should take at least 1,000 mcg cyanocobalamin every day.) If you get a B12 injection, the likelihood of it triggering acne may only be about one in ten.

I have much more detailed information on B12 and acne here:

To learn more about vitamin B12, visit our topic page, which covers a broad range of the latest evidence-based research.


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

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