How long it takes for a subcutaneous hematoma to form a hard mass to be absorbed depends largely on the size of the subcutaneous hematoma. Most subcutaneous hematomas are caused by trauma. Usually, a mass formed by a subcutaneous hematoma less than 2 cm in diameter can be completely absorbed in about 7-10 days. In the case of a hard hematoma of 2-5 cm in diameter, the absorption time may be longer, usually taking about 3 weeks to subside. For hematoma hard masses over 5 cm in diameter, it is usually difficult to absorb on its own and requires waiting for the mass to liquefy and then performing a puncture aspiration to remove the fluid, a process that may take 3-4 weeks. In addition, during the recovery period of subcutaneous hematoma hard masses, patients can take appropriate oral blood-stasis activating drugs, such as blood-stasis activating capsules, which can promote the absorption of local blood stasis. If the hard mass formed by the hematoma is larger or produces local pressure symptoms, the patient should preferably undergo surgical excision treatment.