Vitamin B12: How Much and How Often?

Image Credit: kokopinto / Flickr. This image has been modified.

Vitamin B12 is not made by plants or animals, but by microbes that blanket the earth. In today’s sanitized, modern world, the water supply is commonly chlorinated to kill off any bacteria. So, while we don’t get much B12 in the water anymore, we don’t get much cholera either, which is a good thing! A regular, reliable source of B12 is critical for anyone eating a plant-based diet. 

What does the latest research on B12 say?

  • At least 2,000 mcg (µg) cyanocobalamin should be taken once each week, ideally as a chewable, sublingual, or liquid supplement taken on an empty stomach
  • OR, at least 50 mcg of supplemental cyanocobalamin should be taken daily (you needn’t worry about taking too much)
  • OR servings of B12-fortified foods should be eaten three times a day (at each meal), and each serving should contain at least 190% of the Daily Value listed on the nutrition facts label*

                    * Based on the new labeling that started January 1, 2020, the target is 4.5 mcg three times a day.

If you’re over 65 years of age, you should take at least 1,000 mcg (µg) cyanocobalamin every day.

Tip: If you’re experiencing deficiency symptoms, the best test is a urine MMA, not serum B12 level.

For more information on vitamin B12, including recommended doses for children, see our additional resources:

–Michael Greger, M.D. FACLM

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