Blood in urine may be physiological, or it may be caused by urinary tract infections, urinary stones, tumors and tuberculosis. 1. Urethral infection: it is an infectious disease caused by different pathogens, which leads to low immunity as well as inflammatory infections, which in turn cause damage to the mucous membranes of the urinary tract, thus leading to symptoms such as blood in the urine and irritation of the urinary tract. 2. Stones: If stones grow inside the urinary tract, they can also cause damage to the epithelium of the urinary tract, resulting in blood in the urine. 3. Tumor: if you suffer from a series of malignant tumors of kidney, ureter, bladder, urethra and so on, it will also induce symptoms of blood in urine. 4. Urinary stones: patients may have blood in urine when urinating, in addition to lumbar pain and other discomforts. There are other reasons for bleeding in urine when urinating, patients need to consult the doctor in time for examination and early treatment.