Injections into the shoulder or buttocks are called intramuscular injections, and intramuscular injections allow for rapid absorption of the medication to produce its effects. Additionally, many medications cannot be injected into blood vessels and are then injected into the muscle. Intramuscular injection is a commonly used method of injection, usually chosen in the buttocks or shoulders, mainly because these two parts of the human body muscle hypertrophy, not easy to hurt the bone, and the distribution of blood vessels is relatively small, fewer nerve endings reflexes, can reduce the risk of pain and bleeding. Although intramuscular injection is easy to operate, the drug may cause allergies or other adverse reactions after entering the body. And it may also cause local inflammation if it is not sterilized. Therefore, professional treatment should be carried out in regular medical institutions.