What is the cause of red urine in men? First of all, urine with 1ml of blood mixed in 1L of urine can be shown as hematuria. The most likely cause of red urine in men is hematuria, which is usually determined by routine urine tests and morphological examination of urine red blood cells to clarify whether it is hematuria and the source of hematuria. If you have more than 80% abnormal red blood cells, you can think that it is from the renal tubules or some lesions in the kidney unit, such as nephritis; if it is less than 20% abnormal red blood cells, then it may also come from the kidneys or ureter, bladder, and prostate, and the prostate gland is worn bleeding this kind of possibility. The main thing is to be aware of painless carnal hematuria, which is a common symptom of tumors, and to be aware of this, and must be treated promptly.