Intramuscular injection mainly involves injecting medication into the muscle tissue through a syringe for therapeutic purposes. Intramuscular injection is somewhat painful, but the pain is not the same severity, generally based on the drug, muscle tightness, manipulation and other factors to determine the severity of pain. 1. Drugs: If the drug is stimulating or viscous, the pain will be stronger after injection, and on the contrary, the pain will be lighter. Sometimes there is also a relationship with the solvent. Such as intramuscular injection of penicillin, saline as a solvent, the degree of pain is far more benzyl alcohol (due to benzyl alcohol itself on the human body damage, now do not use the solvent) as a solvent to pain. 2. Muscle tightness: If the injection is tense, it will easily cause muscle tightness, and the pain will be more intense. 3. Maneuvering: If the needle is too slow, injecting drugs too quickly, the site is not accurate, etc., will lead to an increase in pain. However, the pain will not last too long and will usually be relieved in a few minutes. Intramuscular injection can be judged from a number of aspects of pain, most people can tolerate, do not need to be too nervous, need to be under the operation of the doctor. Diet should pay attention to low salt and low fat, light and easy to digest, etc..