If you have a low vitamin B12 level, injections can go a long way toward improving your health and well being. But if your B12 level is normal, don't fall for claims that I receive monthly intramuscular vitamin B12 (cobalamin) injections, but my serum B12 level measured two weeks after the injection is only 268 pg mL; why is it low and how should the dosing Vitamin B 12 Injections B12 Shots Cincinnati Vitamin B12 injections for MTHFR: Injection or sublingual B12? Methyl Life Supplements When Do You Feel Less Tired After B12 Shot? 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.