Post-phlebotomy bruising is a manifestation of blood leaking out of blood vessels and seeping into the subcutaneous tissue, which usually fades on its own in about 2 weeks. The bruise after venous blood sampling can be applied with cold compress within 24 hours, and after 24 hours, local hot compress can be given, or potato slices can be applied externally to promote the bruise dissipation quickly, and other special treatment is not needed, usually the bruise will dissipate naturally after 2 weeks, so there is no need to worry too much. The reason for this symptom is that the blood collection needle is relatively thick when collecting blood from the vein, and after puncturing the blood vessel to collect blood, the puncture hole does not get the exact pressure or the pressure time is not enough, which causes the blood to seep out of the blood vessel along the puncture hole and free to the subcutaneous tissue, which will show the bruising performance from the skin surface. If the bruising is extensive, routine blood tests as well as coagulation functions are needed to rule out bruising due to thrombocytopenia and coagulation factor deficiency. Patients are advised to press the bleeding spot with a cotton swab after phlebotomy, but not to press the bleeding site, and should minimize activity or brake treatment to avoid re-bleeding from the bleeding spot.