Vitamin B12

Supplement Forms/Alternate Names

Cobalamin, cyanocobalamin, hydrocobalamin, methylcobalamin


Vitamin B12 is found in seafood, dairy, and eggs. The body uses B12 to keep nerve cells and blood cells healthy. Vitamin B12 has been used for pregnancy support and to improve mental well-being. It has also been used to improve bone, lung, and heart health. It is used to manage vitamin B12 deficiency. Vitamin B12 can be taken as a pill, powder, or tincture. It can also be injected into the bloodstream or muscle by a healthcare provider.


2.4 micrograms for adults

3000 to 5000 micrograms daily for vitamin B12 deficiency

What Research Shows

Likely Effective

May Be Effective

  • Shingles —likely to improve quality of life in those with postherpetic neuralgia F1

Unlikely to Be Effective

Not Enough Data to Assess

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Safety Notes

It is likely safe to take vitamin B12 in small doses for a short time. Not enough studies have been done to say whether it is safe to take for a long period.

Weakness, skin tingling, and headache may happen in some people. Women who are pregnant or breastfeeding should not take large doses of vitamin B12.


Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse, such as:

  • People taking nasal medicines or bone marrow suppressants should talk to their doctors before taking this vitamin.
  • People with infection, iron deficiency, Leber disease, megaloblastic anemia, renal impairment, or blood in their urine should talk to their doctors before taking this vitamin.
  • Talk to your child’s doctor before giving this vitamin to a premature infant.


A. Depression

A1. Almeida OP, Ford AH, et al. Systematic review and meta-analysis of randomized placebo-controlled trials of folate and vitamin B12 for depression. Int Psychogeriatr. 2015;27(5):727-737.

A2. Schefft C, Kilarski LL, et al. Efficacy of adding nutritional supplements in unipolar depression: A systematic review and meta-analysis. Eur Neuropsychopharmacol. 2017 Nov;27(11):1090-1109.

B. Diabetic Peripheral Neuropathy

B1. Xu Q, Pan J, et al. Meta-analysis of methylcobalamin alone and in combination with lipoic acid in patients with diabetic peripheral neuropathy. Diabetes Res Clin Pract. 2013 Aug;101(2):99-105.

B2. Deng H, Yin J, et al. Meta-analysis of methylcobalamin alone and in combination with prostaglandin E1 in the treatment of diabetic peripheral neuropathy. Endocrine. 2014 Aug;46(3):445-454.

C. Infant Support

C1. Strand TA, Taneja S, et al. Vitamin B-12, folic acid, and growth in 6-to 20-month-old children: a randomized controlled trial. Pediatrics. 2015;135(4):e918-926.

D. Lumbar Spinal Stenosis with Neurogenic Claudication

D1. Ammendolia C, Stuber KJ, et al. Nonoperative treatment for lumbar spinal stenosis with neurogenic claudication. Cochrane Database Syst Rev. 2013 Aug 30;(8):CD010712.

E. Osteoporosis

E1. Ruan J, Gong X, et al. Effect of B vitamin (folate, B6, and B12) supplementation on osteoporotic fracture and bone turnover markers: a meta-analysis. Med Sci Monit. 2015 Mar 24;21:875-881.

F. Shingles

F1. Wang JY, Wu YH, et al. Vitamin B12 for herpetic neuralgia: A meta-analysis of randomised controlled trials. Complement Ther Med. 2018;41:277-282.

G. Stroke Prevention

G1. Dong H, Pi F, et al. Efficacy of Supplementation with B Vitamins for Stroke Prevention: A Network Meta-Analysis of Randomized Controlled Trials. PLoS One. 2015 Sep 10;10(9):e0137533.

G2. Spence JD, Yi Q, et al. B vitamins in stroke prevention: time to reconsider. Lancet Neurol. 2017 Sep;16(9):750-760.

Last reviewed July 2019 by EBSCO NAT Review Board Eric Hurwitz, DC
Last Updated: 3/26/2020