Overview
What is vitamin B12?
What are vitamin B12’s main benefits?
What are vitamin B12’s main drawbacks?
How does vitamin B12 work?
Dosage information
The Recommended Daily Allowance (RDA) of vitamin B12 is 2.4 μg for adults without known health conditions. During pregnancy, the RDA increases to 2.6 μg.[1] For children 8 years and under, the RDA is 1.2 μg.[1] Supplementing with B12 is probably not helpful in people who are able to get enough of the vitamin through their diet and have no difficulty with absorption.
Supplements that are available over the counter contain 500–2000 μg of vitamin B12 per tablet. Long-term use is not recommended without monitoring of vitamin B12 levels.
For replenishing stores of vitamin B12, 1000 μg should be given by intramuscular injection three times per week for two weeks. This can then be done weekly for four weeks, then once monthly. In cases where absorption is not an issue, the maintenance dose can also be given orally.[2]
Examine Database: Vitamin B12
Research FeedRead all studies
In this 12-month randomized controlled trial in 160 participants with type 2 diabetes, taking a vitamin B12 supplement improved HbA1c.
Frequently asked questions
Is there a test for vitamin B12 deficiency?
What causes vitamin B12 deficiency?
What are other names for Vitamin B12?
Update History
Full FAQ and database update
References
Examine Database References
- Fatigue Symptoms - Huijts M, van Oostenbrugge RJ, Rouhl RP, Menheere P, Duits AEffects of vitamin B12 supplementation on cognition, depression, and fatigue in patients with lacunar strokeInt Psychogeriatr.(2013 Mar)
- Homocysteine - Hill MH, Flatley JE, Barker ME, Garner CM, Manning NJ, Olpin SE, Moat SJ, Russell J, Powers HJA vitamin B-12 supplement of 500 μg/d for eight weeks does not normalize urinary methylmalonic acid or other biomarkers of vitamin B-12 status in elderly people with moderately poor vitamin B-12 statusJ Nutr.(2013 Feb)
- Depression Symptoms - Markun S, Gravestock I, Jäger L, Rosemann T, Pichierri G, Burgstaller JMEffects of Vitamin B12 Supplementation on Cognitive Function, Depressive Symptoms, and Fatigue: A Systematic Review, Meta-Analysis, and Meta-Regression.Nutrients.(2021-Mar-12)
- Depression Symptoms - Almeida OP, Ford AH, Flicker LSystematic review and meta-analysis of randomized placebo-controlled trials of folate and vitamin B12 for depression.Int Psychogeriatr.(2015-May)
- Schizophrenia symptoms - Chen CH, Chiu CC, Chiu YH, Chang CH, Chang YH, Huang MC, Lu ML, Chen PYFolate and vitamin B12 supplementation in patients with schizophrenia and low serum folate level: A 24-week randomized, double-blind, placebo-controlled study.J Formos Med Assoc.(2024 Dec 7)