Why Do I Feel Worse After My B12 Injection? PA Relief Vitamin B 12 intramuscular injections are also used therapeutically to help restore energy and combat various symptoms related to such deficiencies. Vitamin B 12 is essential to the development of healthy blood cells, nerve B12 Injections and IV Infusion Treatments to Boost Your Vitality Why Your B12 Shots Are Not Working 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. B12 deficiency can damage your nervous system with a completely normal blood count. In a landmark NEJM study, 28% of patients with neuropsychiatric B12 damage had no anemia or macrocytosis. B12 runs