Small blood clots in the urine, the urine test is normal may be a transient mucosal bleeding, the most common cause is injury, urinary tract infection, stones and other diseases lead to. 1. injury: if there is frequent, intense masturbation or sexual life, there may be damage to the mucous membrane of the urethra, resulting in mucosal bleeding, mucosal injury healed quickly, the urine routine will be normal. 2. Urinary tract infection: the infection causes the patient to appear frequent urination, urinary urgency, urinary pain symptoms, can also appear hematuria, if the examination of the urinary tract infection has been cured, the urine test may be normal. 3. urinary stones: if the stone is relatively small, the discharge process may cut the urethral mucosa, resulting in blood clots in the urine, if completely discharged, the examination of the urethral mucosa repaired, the urine routine is not a problem. If the urine routine is normal, you can temporarily observe to see, if the blood clots appear again should go to the hospital. Improve the relevant examination to clarify the specific cause of the disease.