Vitamin B12 injections are generally considered to be very safe. They have no major side effects. However, in very rare cases, some people can experience side effects caused by allergic reactions or sensitivity ( 29 , 30 ). If you experience any side effects, speak with your doctor.

Is vitamin B12 injections subcutaneous or intramuscular?

Vitamin B12 is rapidly absorbed from intramuscular (IM) and subcutaneous (SC) sites of injection; peak plasma concentrations are reached within 1 hour after IM injection.

How do you give a B12 shot in the arm?

The injection site will be in the muscle directly below your two fingers. Think of a triangle and you will insert the needle in the center of the triangle. (Picture 4-D). Location of the bone at the top of the arm Injection site Page 6 The Angle of the needle: The needle must go into the skin at a 90° angle.