Cant swallow your Vitamin B12 tablet? Dont quit., Most people think tablet = only option., Thats not true., If B12 tablets cause, nausea, bad smell, metallic taste, gag reflex, You still Signs You May Have a B12 Deficiency Understanding the B12 Vitamin Shot: Benefits, Risks, and Dosage Guide Vitamin B12 Side Effects: Risks of Excess Intake B12 Shots at Home: How, Where & How Often to Inject Yourself AZ IV Medics Low B12 levels can lead to fatigue, numbness, irritability, and moreyet many people don't realize they're deficient. The good news? Testing and treatment are simple with options like injections or dissolvable tablets.