Injection is the act of injecting into the body, through a needle (hypodermic needle to be more specific), a drug / liquid compatible with the human blood / intervention to cure a disease, hence having a widespread fear of needles is normal in many people. If the administration site is deeply rooted and is not to be done on your own, it can not be self-administered. You need professionals qualified to safely administer the injection into your body ensuring the much-needed sterility of things to avoid collateral harm or infection.