Injection is the process of injecting a drug/liquid compatible with the human blood/ intervention to treat a disease, into the body through the help of a needle (hypodermic needle to be more specific), thus having a prevailing fear of needles is common in many people. It cannot be self administered if the site of administration is deep seated and must not be practiced on your own. You need professional people who are trained to administer the injection safely into your body providing the much needed sterility of things to prevent any collateral damage or infection.