However, some rare side effects of too much vitamin B12 can include: Headache Weakness Nausea Diarrhea Tingling sensations in the hands and feet Allergic reactions or skin rash (uncommon) When To Seek Medical Advice Risk of vitamin B12 deficiency: Groups at a higher risk of vitamin B12 deficiency include older adults, people who only eat plant-based foods (vegans and vegetarians), and those with certain chronic conditions (gastrointestinal disorders that can affect vitamin absorption)
However, the publicly available evidence does not support broad conclusions about complete toxicological safety, long-duration exposure, reproductive or developmental risk, immunological risk, genotoxicity, or suitability for any non-research application
Key considerations for oral formulations: Convenient: Familiar to most patients and easily integrated into daily routines without clinic visits
Vitamin B12 shots are especially helpful for certain groups of people, including: Vegetarians and vegans : Since B12 is mostly found in animal products, those who avoid meat may have lower levels