Blood in urine in the elderly may be caused by acute injury, urinary tract infection, urinary stones, urinary tract tumor and other factors. 1. Acute injury: for example, external blows, resulting in local damage to the urinary system, causing bleeding, it will lead to blood in the urine, may also be accompanied by pain, swelling and other symptoms. 2. Urinary system infection: when there is an infection in the urinary system, resulting in localized damage and bleeding, blood in the urine will occur, such as cystitis, which may also be accompanied by pain in urination, frequent urination, urinary urgency and other symptoms. 3. urinary stones: for example, bladder stones, may be related to long time holding urine, metabolic abnormalities in the body and other factors, the stones may lead to damage to the bladder, there will be hematuria, may also be accompanied by difficulty in urination, urination pain and other symptoms. 4. Urinary system tumor: when the tumor surface tissue necrosis, may cause bleeding, there will be blood urine visible to the naked eye, for example, bladder tumor, there may also be lower abdominal swelling, difficulty in urination and other symptoms. If the elderly have blood in urine and there are other abnormal manifestations, it is recommended to consult a doctor for examination and treatment to avoid delaying the condition.