How do I make sure I do not hit a blood vessel or a muscle when I give my son his insulin shot? I’ve noticed on a few occasions the area in which I give the shot turns black and blue, or bleeds a tiny bit after the shot.

The probable reason for the bruising is that you are giving the insulin intramuscularly using an ordinary length needle and holding it perpendicular to the skin. Muscle has a much richer blood supply than subcutaneous tissue. You should either use the ultrafine short needle which is unlikely to reach muscle however you inject, or if you continue with standard needle, you need to pinch up the skin and inject at around thirty degrees to the skin surface.

DOB
Additional comments from Linda Mackowiak, diabetes nurse specialist:
Bruising occasionally is common, as is a little drop of blood. You may have
just nicked a superficial capillary (very small blood vessel) and is of no
concern. If bruising or bleeding is happening frequently, then see your
doctor or diabetes educator for individual advice in injection technique or
further evaluation. Concerning the angle of injection with insulin syringes,
unless the person is extremely thin, the insulin syringe is held
perpendicular to the skin (90 degrees). It is important to lift up the skin
to make sure that the injection does not go in too deeply, but rather the
insulin is given into the fatty tissue just under the skin.

LM