- Dermatologic: Itching, rash, transitory exanthema, and urticaria have been reported. Vitamin B12 has been associated with cases of rosacea fulminans, characterized by intense erythema with nodules, papules, and pustules. Symptoms may persist for up to 4 months after the supplement is stopped, and may require treatment with systemic corticosteroids and topical therapy.
- Gastrointestinal: Diarrhea has been reported.
- Hematologic: Peripheral
vascular thrombosis has been
reported.Â
- Leber's disease: Vitamin B12 in the form of cyanocobalamin is contraindicated in early Leber's disease, which is hereditary optic nerve atrophy. Vitamin B12 can cause severe and swift optic atrophy.
Pregnancy and breastfeeding
Vitamin B12 is likely safe when used orally in amounts that do not exceed the recommended dietary allowance (RDA). The RDA for vitamin B12 in pregnant women is 2.6mcg per day and 2.8mcg during lactation periods.There is insufficient reliable information available about the safety of consuming greater amounts of Vitamin B12 during pregnancy.
