Bruising of the arm after drawing blood is mainly caused by bad compression after drawing blood, strong permeability of blood vessels or abnormal coagulation function of the patient, and how to deal with it depends on the specific situation of the patient. If the bruise is very light, it can be observed without any treatment. If the bruise is large and shows aggravation, the patient’s coagulation function and blood routine need to be checked first to determine whether there is any abnormality in the coagulation function. If there is any abnormality of coagulation function, medication or blood transfusion is needed according to the situation. If the patient’s coagulation function is not abnormal, the main consideration is that the pressure is not good or the brittleness of the blood vessel increases, you can choose to press the hemostasis or ice hemostasis, and so on, after the situation is stabilized, the blood clots or the bruises on the arm no longer increase, the patient can choose to use hot compresses, the use of magnesium sulfate wet compresses, or the use of rhubarb, manganese nitrate and other traditional Chinese medicines that activate the blood circulation and eliminate blood stasis, which will dissipate the bruises in a timely manner.