What is hematuria? It is the presence of red blood cells mixed in the urine. Routine urine microscopy can be called hematuria when the number of red blood cells is greater than 3 per high magnification field of view. 0.5~1 ml of blood in 1 liter of urine can be seen as hematuria with the naked eye. Therefore, according to the amount of bleeding, hematuria is divided into microscopic hematuria and naked-eye hematuria. Although the severity of both hematuria is different, they have the same clinical significance. In some patients who present with hematuria, blood clots are also present. Since carnal hematuria often appears suddenly, patients are very fearful and anxious and often seek medical attention with great anxiety. Patients tend to ignore intermittent hematuria, and when it stops, they are often not eager to go to the doctor, thus delaying treatment. Microscopic hematuria is difficult to detect because it lacks the attention-grabbing blood color. Hematuria is only a symptom, and the next thing we need to address is the cause of the hematuria. We generally start by dividing hematuria into medical and surgical hematuria. Internal hematuria mainly refers to hematuria originating from the kidneys, often accompanied by tubular and obvious proteinuria, such as nephropathy or nephritis, and other renal hematuria. Surgical causes of hematuria mainly include urinary tract inflammation, urinary tract stones, urinary tract tumors, and less commonly, urinary tract and vascular malformations and active hematuria. In fact, 95% of the hematuria patients seen in the outpatient clinic are caused by benign diseases. These can often be diagnosed by general tests such as routine urine and ultrasound. What we cannot ignore is the hematuria due to urinary tract tumors, which we are not allowed to miss. Some patients must be diagnosed by CT or MRI examinations, or even by some minimally invasive examinations such as cystoscopy or ureteroscopy techniques. However, we should never, and should not, abuse these invasive tests. For clinicians, detailed history taking, careful physical examination, and targeted ancillary examinations are extremely important. We should consider the patient’s gender, age, other symptoms associated with hematuria, and duration of illness to make a reasonable judgment and give appropriate tests.