Skip to main content

Vitamin B-12 injections for weight loss: Do they work?

Medically reviewed by Last updated on Sep 13, 2022.

There's no solid proof that vitamin B-12 shots, also called injections, help you lose weight.

Vitamin B-12 is a water-soluble B complex vitamin. It's found naturally in many foods, such as meat, fish and dairy products. Vitamin B-12 is added to some foods and is available as a dietary supplement. Health care providers commonly prescribe vitamin B-12 shots to help prevent or treat pernicious anemia and B-12 deficiency.

Some researchers have studied vitamin B-12 to find out if it can raise energy and endurance during exercise. But there isn't evidence to prove this. And unless you have low vitamin B-12 levels in your body, vitamin B-12 shots aren't likely to give you more energy or improve your performance.

Metformin (Fortamet, Riomet, others) is a drug that may be used as part of a weight-loss tool for people with type 2 diabetes. Low vitamin B-12 levels in your body can be a side effect of this drug. If you take metformin, talk to your health care provider about ways to keep enough vitamin B-12 in your body.

Getting large amounts of vitamin B-12 through vitamin B-12 shots is not likely to harm your health. But vitamin B-12 may affect how well some drugs work. And some drugs can affect vitamin B-12 levels. So if you want to get vitamin B-12 shots, tell your health care provider first.

If you're hoping to lose weight, avoid giving in to quick and easy fixes. What counts is a healthy lifestyle. Enjoy healthier foods in proper portions. And get physical activity every day.

© 1998-2023 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. Terms of use.