In principle, insulin needles for injection can only be used once and should be replaced once for each injection. If the needle is not replaced for a long time, the needle will be deformed and the tip will become blunt and thicker, which will lead to pain and discomfort at the injection site and even bleeding, and the needle will be easily bent and folded into the subcutaneous tissue. In addition, long time will lead to blockage of insulin needles, and insulin will easily accumulate at the needles and cannot be injected smoothly into the subcutaneous tissue, which will affect the effect of lowering sugar and increase the risk of skin infection, so it is recommended to use insulin needles at once.