There are rare reports of acneiform and hypersensitivity responses, although these cannot be completely distinguished from reactions to, e.g., excipients.
There are rare reports of acneiform and hypersensitivity responses, although these cannot be completely distinguished from reactions to, e.g., excipients.
Observational studies associate B12 supplementation and higher circulating B12 levels with increased risks of malignancy. However, these findings are inconsistent, and current evidence is insufficient to establish causality, as potential reverse causation remains a major concern.
Overall, supplementation has not shown consistent benefits in populations without overt clinical or biochemical B12 deficiency, with no clear improvements in fatigue, mood, cognition, or cardiovascular outcomes.
Effect
Neutral
Effect size
Small
Significant
No
Dose
0.02 to 1 mg/day orally and 1 to 5 mg/week intramuscularly, durations ~4 weeks to ~7 years