Cyanocobalamin (B12) Injection 1000 mcg mL, Multiple Dose Vial 30 mL McGuff Treatment with high dose vitamin B12 been shown to be safe How Quickly Do Vitamin B12 Injections Work? Prime Aesthetics A Guide to Vitamin B Complex Injection Benefits and Dosage B12 Shots Dosage for Adults: How Much, How Often, and Key Injection Guidelines Liv Hospital Cyanocobalamin is the preferred supplemental form of vitamin B 12 as there is insufficient evidence to support the efficacy of the other forms like methylcobalamin. Michael Greger MD, How Not to Die.