vitamin b12 injection where on body A Vitamin B12 is a quick shot that gives your vitamin B12 directly into the muscle. This helps your body absorb it faster than tablets. Vitamin B12 helps B12 vitamin Store A Manual

This article examines the main differences between methylcobalamin and cyanocobalamin two of the most common sources of vitamin B12 found in supplements

Third, aggregated peptides and immunogenicity

This includes confirmed low serum vitamin B12 levels, pernicious anaemia, malabsorption states such as coeliac disease, inflammatory bowel disease, or post-gastric or bariatric surgery, unexplained anaemia, neuropathy or neurological symptoms consistent with vitamin B12 deficiency, a long-term vegan diet with symptoms or low levels, or failure of oral vitamin B12 supplementation

Summary: B12 injections begin working at a cellular level immediately, though noticeable symptom improvement typically occurs within 4872 hours to several weeks depending on deficiency severity