1- Prepare the injection site using an alcohol pad, but make sure you let the alcohol dry completely. This is probably the most common mistake people make that can cause unnecessary pain. It only takes an extra five seconds and is the easiest way to reduce pain during the injection.
2- Choose the correct site for the injection. The deltoid muscle of the upper arm is the preferred IM injection site, but viscous material or volumes larger than 2.5 ml should be given in the gluteus maximus muscle in the upper, outer quadrant of the buttock. An alternate site for larger injections is the vastus lateralus muscle on the outside of the leg halfway between the knee and the hip. These two larger muscles can accomodate a volume up to 5 ml.
3- Ensure that the needle remains at a 90-degree angle to the skin during the procedure. The needle must penetrate deep into the muscle, and a 90-degree angle puts the needle through as little skin as possible. Skin contains many more nerve endings than muscle and registers far more pain. Changing this angle while the needle is still in the muscle will cause pain in the muscle tissue as well.
4- Grasp a two- or three-inch section of the injection site and squeeze firmly but not painfully. Insert the needle quickly and firmly into the injection site up to the hub of the needle. The injection should not be so fast that it is not well controlled. Take care that you do not use a needle that is too long. Most people do not notice when a bone is hit, but it is possible to damage the needle on a bone and cause pain from a complication.
5- Perform the injection slowly. Injecting anything into the muscle too quickly will cause more trauma to the tissue. However, performing the injection should not cause the person pain because of the length of time the needle is in the arm. The speed of the injection should be about one second per ml for most medications and vaccinations.
6- Gently massage the muscle tissue after the injection has been given and the needle has been removed. The person receiving the injection may prefer to do this especially if the injeciton is in the buttock. If the person shows resistance or reluctance, this step can be optional.