Vitamin B12 Injection Dose for Adults: 7 Key Facts on Dosage & Frequency Liv Hospital Vitamin B12 Monthly Injection Dose: Typical Dosages & Administration Methods Liv Hospital Not all shots are the same here's a guide Injections are a fast, effective way to deliver medications, nutrients, and vaccines directly into the bodybut not all injections are the Vitamin B12 Deficiency Vitamin B12 deficiency happens when the body does not have enough vitamin B12. Vitamin B12 is important for making healthy red blood cells and keeping nerves