Injecting substances can expose individuals that use injection drugs to serious harm, but understanding the difference between safer and more harmful sites can help reduce these potential dangers. Here's a breakdown of 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 Methylcobalamin Injection (Vitamin B12) Empower Pharmacy B12 vitamin Store Intramuscular vs Subcutaneous Injections for vitamin B12 supplements.