Vitamin B-12 Injections For Weight Loss: Do They Work? - Mayo Clinic

Are vitamin B-12 injections helpful for weight loss?

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.

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March 20, 2025 Show references

1. Vitamin B12. Natural Medicines. https://naturalmedicines.therapeuticresearch.com. Accessed Aug. 12, 2022.
2. Healthy weight, nutrition, and physical activity. Centers for Disease Control and Prevention. https://www.cdc.gov/healthyweight/index.html. Accessed Aug. 12, 2022.
3. Wexler DJ, et al. Metformin in the treatment of adults with type 2 diabetes mellitus. https://www.uptodate.com/contents/search. Accessed Aug. 12, 2022.
4. Vitamin B12: Fact sheet for health professionals. Office of Dietary Supplements. http://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/. Accessed Aug. 16, 2022.
5. Boachie J, et al. Low vitamin B12 and lipid metabolism: Evidence from pre-clinical and clinical studies. Nutrients. 2020; doi:10.3390/nu12071925.
6. Raymond JL, et al., eds. Krause and Mahan's Food & the Nutrition Care Process. 15th ed. Kindle edition. Elsevier; 2021. Accessed Aug. 23, 2022.
7. Medical review (expert opinion). Mayo Clinic. Aug. 25, 2022.

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