There are many reasons for microscopic hematuria, which may be caused by nephritis syndrome, urethritis, urinary tumor or urinary stones and other pathological reasons, or physiological reasons such as strenuous exercise. 1. Nephritis syndrome: glomerular injury can appear microscopic hematuria, while microscopic protein and abnormal tubular pattern. 2. Urethritis: due to inflammation stimulation, the whole urethral mucosa appears congestion, oozing blood, so in urinalysis, there will be red blood cells under the microscope, which can be accompanied by urinary frequency, urinary urgency and other symptoms; 3. urinary system tumor: due to tumor bleeding and infiltration caused by microscopic hematuria or hematuria, especially the elderly must pay attention to, it is recommended to go to the hospital to do abdominal ultrasound or cystoscopy and other tests to assist in the diagnosis. 4. Urinary stones: when the stones are active, it will cause damage to the mucous membrane of the urinary system, so there will be microscopic hematuria, accompanied by severe back pain and other symptoms; 5. Physiological reasons: in the case of strenuous exercise, mental tension, etc. will also appear microscopic hematuria, at this time, generally do not need treatment, adjust the lifestyle can be relieved by themselves. The causes of microscopic hematuria are many, it is recommended to go to the hospital in time to find out the cause of the disease, under the guidance of the physician active treatment.