Vitamin B12

Studies in people

• Open question

  Pregnancy health²

  Vitamin B12 supplements in pregnancy may raise vitamin B12 levels, but scientists do not yet know whether they improve other health outcomes.

• Concern

  Folic acid risks³

  In people, high-dose folic acid may worsen vitamin B12 deficiency, but scientists do not yet know for sure.

• Benefit

  Nerve damage in diabetes⁴

  In people with diabetic nerve damage, taking vitamin B12 pills for a year improved nerve tests, pain and quality of life.

• Benefit

  Oral treatment for anemia⁵

  In people with pernicious anemia, taking vitamin B12 by mouth improved their vitamin B12 deficiency.

• Concern

  Skin bacteria and acne⁶

  Vitamin B12 supplements changed skin bacteria in people, and one person got acne.

Study type not stated

• Open question

  Low energy and tingling⁸

  Low vitamin B12 can cause tiredness, brain fog and tingling, and is treated with vitamin B12 pills or shots.

• Concern

  Blood and nerve health¹⁰

  Vitamin B12 deficiency can affect the blood, bone marrow and nervous system, causing anemia and nerve problems.

How it’s made and used

• B12 absorption problems⁷

  Vitamin B12 needs help from the body to be absorbed, and many gut problems can block this.

• How much the body absorbs⁹

  How much vitamin B12 the body absorbs drops as the amount eaten in one meal goes up.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least two findings in people. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.