Recommended Daily Vitamin B12 Supplementation for Adults
For healthy adults, the recommended daily vitamin B12 supplement dose is 2.4 micrograms per day, with higher doses of 1000-2000 micrograms (1-2 mg) daily recommended for those with deficiency or absorption issues. 1
General Recommendations by Population
Healthy Adults
- The World Health Organization (WHO) Recommended Daily Allowance for vitamin B12 is 2.4 micrograms per day for adults 1
- Adults over 50 years should consume vitamin B12 in crystalline form (supplements or fortified foods) rather than relying solely on dietary sources due to decreased absorption with age 2
High-Risk Groups Requiring Higher Doses
- Adults over 75 years may require 500-1000 micrograms daily due to age-related absorption issues 3
- Vegans or strict vegetarians should take vitamin B12 supplements or consume fortified foods to meet requirements 4
- Patients using metformin for more than four months may need supplementation 4
- Patients using proton pump inhibitors or H2 blockers for more than 12 months often require supplementation 4
Therapeutic Dosing for Deficiency
Oral Supplementation
- High-dose oral vitamin B12 (1000-2000 micrograms daily) is as effective as intramuscular administration for correcting deficiency in most cases 4, 2
- Oral doses of 2000 micrograms daily have shown comparable effectiveness to intramuscular injections for hematological and neurological responses 5
Intramuscular Administration (for severe deficiency)
- For patients with severe deficiency or neurological symptoms, intramuscular therapy leads to more rapid improvement 4
- Treatment protocol: 1000 micrograms intramuscularly three times a week for 2 weeks, followed by maintenance treatment of 1000 micrograms every 2-3 months 1
- For neurological involvement: 1000 micrograms intramuscularly on alternate days until symptoms improve, then 1000 micrograms every 2 months 1
Special Populations
Post-Bariatric Surgery
- Patients who have undergone bariatric surgery should receive 1000 micrograms of oral vitamin B12 daily indefinitely 4
- For patients with more than 20 cm of distal ileum resected, 1000 micrograms of vitamin B12 should be administered monthly, typically via intramuscular injection 1
Pregnancy and Lactation
- Pregnant and lactating women require 4 micrograms daily according to the Food and Nutrition Board recommendations 6
- For pregnant women after bariatric surgery, vitamin B12 supplementation should be continued at 1000 micrograms every 3 months via intramuscular injection or 1000 micrograms daily orally 1
Monitoring and Adjustments
- Serum vitamin B12 levels should be monitored in high-risk individuals 4
- Measurement of serum methylmalonic acid should be used to confirm deficiency in asymptomatic high-risk patients with low-normal levels of vitamin B12 4
- Treatment response should be based on symptom resolution rather than solely on serum B12 levels 7
Important Cautions
- Folic acid supplementation can mask vitamin B12 deficiency and should not be given before checking vitamin B12 status 1, 6
- Untreated vitamin B12 deficiency can lead to irreversible neurological damage even if anemia is corrected with folic acid 6
- Patients with pernicious anemia require lifelong vitamin B12 supplementation 6