Blood in urine is hematuria, also known as blood in urine. Normal urine is free of red blood cells and contains only a very small amount of red blood cells. Uncentrifuged urine can have 0 to 2 red blood cells per high magnification field under the microscope, and if it exceeds this number, it can be diagnosed as hematuria. If the eye can see blood-colored urine, or even blood or blood clots in the urine, it is called hematuria with the naked eye. It is worth pointing out that hematuria is not always detectable by the eye. Diseases of the genitourinary system that may cause blood in the urine (hematuria): 1. Urinary stones: These include stones in the kidney, ureter, bladder or urethra. 2, genitourinary infections: such as prostatitis, urethritis, pyelonephritis, renal tuberculosis, cystitis, etc. Differential diagnosis of blood in urine (hematuria): 1. When urination starts as hematuria and then normal, it is usually mostly urinary infection and urethral disease; 2. If urination starts normally and appears near the end, it is mostly cystitis and prostate disease; Potential dangers of hematuria: Since hematuria is not painful, it is often easy to be ignored by patients. Similarly, behind the silent and senseless hematuria, it often signals the onset of a serious disease. Hematuria occurs often intermittently and sporadically. Whenever the hematuria disappears, the patient must not think that the disease has also been eliminated. In fact, such intermittent, painless hematuria is often a clinical manifestation of urological tumors. Once the hematuria suddenly worsens, it is often at an advanced stage of the tumor. According to statistics, among patients with painless hematuria, bladder cancer accounts for almost 50% and kidney cancer accounts for 40%. And most of these tumors occur in middle-aged and elderly people over 40 years old. Therefore, people must be on high alert when painless hematuria occurs in middle age. Hematuria is often a symptom of a disease. When the symptom of hematuria appears, male friends should treat it correctly, go to a regular hospital in time to find out the cause, actively receive treatment after the disease is diagnosed, and avoid giving themselves too much mental pressure.