Vitamin B12 Injection IV or IM Lets do my first B12 injection together This is something Ive been nervous about for a long time, but today I finally did itand it honestly wasnt bad at all. I used the Union Medico needle guide How Long Does It Take Vitamin B12 Injections to Work? B 12 (Methylcobalamin) Therapy MedClub by Dr Jenn 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 Vitamin B12 Monthly Injection Dose: Typical Dosages & Administration Methods Liv Hospital