The subcutaneous injection area on the arm is at the lower edge of the deltoid muscle of the upper arm. Subcutaneous injection is a biological agent or a small amount of liquid injected into the subcutaneous method, suitable for small-dose drug injections, and should not be taken orally and need to occur within a certain period of time the effect of the drug, such as insulin therapy, vaccination and local anesthesia medication and so on. The injection point is mostly selected from the lower edge of the deltoid muscle of the upper arm, both sides of the abdominal wall, the back, thighs and other parts of the anterior lateral. Usually choose the lower edge of the upper arm deltoid muscle vaccination, the location of the thicker subcutaneous tissue, blood vessels and nerves less distribution, injection is not easy to inject the drug into the muscle layer, and the location is easier to observe and choose the specific injection point, easy to operate. Insulin injection can also be selected from the lower edge of the deltoid muscle of the upper arm, long-term injections need to pay attention to maintain local hygiene to avoid bacterial invasion and infection. After subcutaneous injection, we need to pay attention to observe the situation, and inform the medical personnel in case of discomfort to avoid serious accidents.