Very first step to give injection to any patient is cleaning of the site where injection need to be applied, cleaning must be done in a circular fashion, starting from centre towards periphery like in whirlpool.
Now understand the techniques to give injections.
Intradermal injections are given by pulling the skin tight, insert the needle, bevel up, holding it an angle of 10 degrees as it penetrate skin, turn the needle bevel down and inject a small amount of medication into the skin at junction of epidermis and dermis, until a wheel appears, slowly inject all medication, have a look at the photograph shown. You can watch out the video below on how to give intradermal injection at you tube.
Subcutaneous injections, here amount of medication is around 1 ml, given by holding the needle at 45 degree angle while piercing the skin, skin is pinched tight, insert needle so that hub of needle shaft touches the skin, aspirate to check the location of needle. If blood is aspirated, withdraw the needle and try at other site, if not gently push the medication into subcutaneous tissue, withdraw needle and gently massage the area to help in absorption, never massage insulin or other drug which stains the skin.
Intramuscular injections are given at 90 degree to the skin, penetrate deep, aspirate to check whether you have puncture an artery, vein or nerve, if blood comes, withdraw the needle, change position, new needle should be used, because blood gets clotted in that old needle, as well now a days disposable syringes are used, and push the medication deep in muscle.
How to give injection without pain or discomfort to patient?
Here comes the experience part, give injection by stretching the skin apart, so that nerve endings are spread apart, so when you prick needle, less number of nerve endings are damaged, making it less painful, even you can apply local anesthesia over part where you are giving injection.
Never do following things
Never touch needle by cotton, as seen in films, wiping it in outward fashion, it contaminates needle with microbes.
Never keep air bubbles in medication while giving intravascular injections, however , small air is beneficial in giving intramuscular injections.
Never reuse the needle
Never touch the cap of medication ampule.
Image credits: from http://medicalimages.allrefer.com
watch out the video below on how to give intramuscular injections.