Recommended Daily Vitamin B12 Intake
The recommended daily intake of vitamin B12 for adults is 2.5-4 μg per day, with higher doses of 250-350 μg daily recommended for those at risk of deficiency or with absorption issues. 1
General Recommendations by Population
For Healthy Adults:
- European Food Safety Authority (EFSA) guideline: 4 μg/day 2
- German Nutrition Society guideline: 3 μg/day 2
- UK Reference Nutrient Intake (RNI): 1.5 μg/day (notably the lowest in Europe) 2
For High-Risk Groups:
- Vegans and vegetarians: 250-350 μg daily or 1000 μg weekly 1
- Adults over 75 years: Consider supplementation of 250-350 μg daily 1, 3
- Post-bariatric surgery patients: 1000 μg daily indefinitely 1, 3
- Patients with Crohn's disease (ileal involvement): 1000 μg monthly 1
- Pregnant and lactating women: 4 μg daily 4, 5
Absorption Considerations
Vitamin B12 absorption is a key factor in determining appropriate intake:
- The intrinsic factor-mediated intestinal absorption system becomes saturated at approximately 1.5-2.0 μg per meal 6
- Bioavailability significantly decreases with increasing intake per meal 6
- Bioavailability varies by food source:
- Fish meat: approximately 42%
- Sheep meat: 56-89%
- Chicken meat: 61-66%
- Eggs: poor absorption (<9%) 6
Special Considerations
For Deficiency Treatment:
- Oral supplementation: 1000-2000 μg daily is as effective as intramuscular administration for correcting anemia and neurologic symptoms 1, 3
- Intramuscular therapy: 1000 μg monthly for more rapid improvement in severe deficiency 1, 3
For Prevention in High-Risk Groups:
- Patients on metformin for >4 months should be monitored for B12 deficiency 1
- Patients using proton pump inhibitors or H2 blockers for >12 months are at increased risk 3
- Supplementation with fortified foods or supplements is recommended for those >50 years 3
Safety Considerations
- Total daily intake of folic acid should not exceed 1000 μg (1.0 mg) unless prescribed by a physician, due to potential concerns about masking timely detection of B12 deficiency 2
- However, recent evidence indicates that food fortification has not led to a major increase in masking of vitamin B12 deficiency 2
- Research suggests that daily doses of 647-1032 μg of cyanocobalamin are associated with 80-90% of the maximum reduction in plasma methylmalonic acid concentration in those with mild deficiency 7
Vitamin B12 is water-soluble and excess is typically excreted, making toxicity rare even at high supplemental doses. The focus should be on ensuring adequate intake, particularly for those at risk of deficiency.