Vitamin B12 Injection IV or IM B12 Injections Vitamin B12 Therapy Hanover, MA ALDA Aesthetics How Long Does It Take Vitamin B12 Injections to Work? Instruction Guide for Intramuscular (IM) Self injection of B12 Methylcobalamin 1mg 5mg Injections are a fast, effective way to deliver medications, nutrients, and vaccines directly into the bodybut not all injections are the same. There are five main types. Intramuscular (IM) injections deliver