How Long Does It Take Vitamin B12 Injections to Work? Vitamin B12 overdose: Side effects of taking too many supplements; know when to stop Vitamin B12: How much is too much? Health News The Indian Express Why Do I Feel Worse After My B12 Injection? Causes & Management Bolt Pharmacy B12 Injection Dosage and Frequency: 7 Essential Guidelines for Adults Liv Hospital Vitamin B12 (cobalamin) and folate (vitamin B9) are vitamins that serve important functions in the human body. Folate is needed for development and growth of cells (including red blood cells) and synthesis