Vitamin B12

Vitamin B12 is needed for nerve function and red blood cell formation, and the recommended intake rises slightly in pregnancy. It is found in animal foods and fortified foods, so people who eat no animal products usually need a supplement or fortified foods. Many prenatal vitamins contain B12.

People who are pregnant or planning pregnancy, particularly vegans, vegetarians or people with absorption problems. Whether it suits you depends on your health, medicines and test results — ask a clinician.

The recommended daily intake in pregnancy is 2.6 mcg from food and supplements. People who eat no animal products often need a supplement or fortified foods; ask your provider about dose. Doses vary by product and person; this is not personal medical advice.

B12 is stored in the liver, so deficiency can develop slowly.

Generally well tolerated; rarely, mild stomach upset or skin reactions.

Forms of B12 vary (for example methylcobalamin and cyanocobalamin); evidence that one is better for most people is limited.

Evidence level (our editorial summary, not a formal grading): Established for deficiency.

Pregnancy & breastfeeding: Recommended intake in pregnancy is 2.6 mcg per day; ask your provider whether your prenatal vitamin covers it.

Medication interactions: Metformin and acid-reducing medicines can lower B12 levels.

Talk to a healthcare professional before use if you are pregnant, breastfeeding, planning pregnancy, have a medical condition, take any medicine, or are scheduled for surgery. Dietary supplements are not approved by the FDA for safety or effectiveness before they are sold, and quality varies between products.

Reliable sources to check: NIH Office of Dietary Supplements fact sheets · NCCIH Herbs at a Glance · MedlinePlus Herbs & Supplements · FDA — Dietary Supplements