Optimal Vitamin B12 Dosage and Treating Deficiency 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 B12 injections deliver high doses of this essential vitamin directly into your bloodstream for better absorption than oral supplements to boost energy, support red blood cell production and maintain nerve function. Vitamin B12 Injection Dose for Adults: 7 Essential Dosage Facts & Schedules Liv Hospital Optimal Vitamin B12 Dosage and Treating Deficiency Cyanocobalamin vs Hydroxocobalamin (Vitamin B12 forms) Key Clinical Differences Hydroxocobalamin is preferred in: Pernicious anemia Severe vitamin B12 deficiency Neurological symptoms (subacute combined degeneration, neuropathy) Cyanocobalamin is