In mathematics, the term injection refers to an injective function.

In medicine, an injection is a method of putting liquid into the body with a hollow needle and a syringe.

There are generally three types of injections - subcutaneous injections, intramuscular injections and intravenous infusions.

A person with Type I diabetes typically injects insulin subcutaneously. Places on the body where people can inject insulin most easily are:

  • The outer area of the upper arm.
  • Just above and below the waist, except the area right around the navel (a 2-inch circle).
  • The upper area of the buttock, just behind the hip bone.
  • The front of the thigh, midway to the outer side, 4 inches below the top of
  • the thigh to 4 inches above the knee.

These areas can vary with the size of the person. Changing the injection site keeps lumps or small dents called lipodystrophies from forming in the skin. However, people should try to use the same body area for injections that are given at the same time each day-for example, always using the stomach for the morning injection or an arm for the evening injection. Using the same body area for these routine injections lessens the possibility of changes in the timing and action of insulin.