Recommended Daily Intake of Vitamin B12 (Cobalamin)
The recommended daily intake of vitamin B12 for healthy adults is 2.4 micrograms per day according to the World Health Organization guidelines, though European guidelines suggest higher intakes of 4-6 micrograms per day may be more appropriate for optimal health. 1
Regional Guideline Variations
- The UK Reference Nutrient Intake (RNI) for vitamin B12 is 1.5 μg/day for adults aged 15+ years, which is the lowest recommendation in Europe 2
- The German Nutrition Society recommends a higher intake of 3 μg/day 2
- The European Food Safety Authority (EFSA) recommends 4 μg/day, noting that intakes between 4.3 and 8.6 μg/day are associated with normal ranges of functional markers 2
- Comprehensive analysis of vitamin B12 status alongside intake in Danish postmenopausal women found that 6 μg/day was required to normalize all parameters in individuals with normal absorption capacity 2
Special Populations and Considerations
- Adults over 50 years should obtain vitamin B12 from supplements or fortified foods due to decreased protein-bound B12 absorption related to age-associated atrophic gastritis 3
- Vegans or strict vegetarians require regular B12 supplementation as vitamin B12 is primarily found in animal foods (meat, milk, eggs, fish, and shellfish) 4, 5
- Patients who have undergone bariatric surgery should receive 1 mg (1000 μg) of oral vitamin B12 daily indefinitely 6
- Elderly populations (>65 years) have a higher prevalence of vitamin B12 deficiency, with estimates ranging from 10-40% in community-dwelling and institutionalized elderly 2
- Pregnant women after bariatric surgery should continue vitamin B12 supplementation at 1000 μg every 3 months via intramuscular injection or 1000 μg daily orally 1
Therapeutic Dosing for Deficiency
- For vitamin B12 deficiency treatment: 1000-2000 μg (1-2 mg) daily is recommended 1, 6
- Severe deficiency with neurological symptoms: 1000 μg intramuscularly three times weekly for 2 weeks, followed by maintenance treatment of 1000 μg every 2-3 months 1, 7
- Oral high-dose vitamin B12 (1-2 mg daily) is as effective as intramuscular administration for correcting anemia and neurologic symptoms in most cases 6
Absorption Considerations
- Absorption of crystalline vitamin B12 does not decline with age, but protein-bound B12 absorption decreases in elderly due to atrophic gastritis 3
- The intrinsic factor-mediated intestinal absorption system is saturated at approximately 1.5-2.0 μg per meal under normal physiological conditions 5
- Bioavailability of vitamin B12 varies by food source: fish meat (42%), sheep meat (56-89%), chicken meat (61-66%), and eggs (<9%) 5
- Patients with more than 20 cm of distal ileum resected require 1000 μg of vitamin B12 monthly, typically via intramuscular injection 1
Clinical Pitfalls and Cautions
- Folic acid supplementation can mask vitamin B12 deficiency and should not be given before checking vitamin B12 status 1
- Screening average-risk adults for vitamin B12 deficiency is not recommended, but may be warranted in high-risk patients (those with gastric/intestinal resections, inflammatory bowel disease, long-term metformin or acid-suppressing medication use, vegans, and adults >75 years) 6
- Diagnosis of deficiency can be challenging due to diverse symptoms and differences in diagnostic assay performance 7
- Neurological symptoms of B12 deficiency can occur without hematological abnormalities, and these neurological effects may be irreversible if not treated promptly 2