Expert Q&A

Vitamin B12: How much should you take?

I’ve heard B-12 absorption decreases with age.  How do I know how much I need to take?

-Tia from Minnesota

Vitamin B12 is a complicated nutrient.  Adults need a mere 2.4 micrograms per day.  The main food sources are meats and animal products, so strict vegetarians are at risk of deficiency.  The B12 in food must be released by stomach acid, and then bound to a substance called intrinsic factor, which enables B12 to be absorbed into the body.  Insufficient stomach acid or a lack of intrinsic factor will drastically reduce absorption.  May older adults have one or both of these problems. In addition, many common prescription drugs can interfere with absorption, including drugs for ulcers, reflux disease and metformin for diabetes

How do you know if you have a B12 deficiency?

The only reliable way is through a lab test ordered by your doctor. If your doctor finds you are deficient and your absorption is compromised, you may need shots of B12. You may also be put on a high dose supplement because the form of B12 in supplements is not dependent on stomach acid for absorption. 

B12 is found in multivitamins. Some senior multiples have as much as 10 times the recommended intake.  If you’re taking a supplement, check the label for B12. You might already be getting plenty of B12 from your supplement. 

Just a note: A B12 deficiency causes a distinctive type of anemia. This anemia is linked to several problems common to the elderly: fatigue, poor memory, dementia, confusion, loss of appetite and weakness. Of course, these problems have many other possible causes. If you are suffering from these symptoms, talk to your doctor about a possible link.

Donna Feldman, MS, RD
Contributing Expert

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