Blood in the urine can be a sign of an underlying disease, or it can be something that happens briefly and then goes away. A primary care physician or a urologist can help to determine if the blood in the urine is an indicator of disease or not. There are many causes of blood in the urine. The most serious cause of blood in the urine is cancer, usually cancer of the prostate, bladder, or kidney. This is more likely to happen in older people. A very frequent cause of blood in the urine is a urinary tract infection. Other symptoms that point to a urinary tract infection include pain while urinating, urinating more often than normal, and cloudy urine. Kidney stones can also lead to blood in the urine. Usually, people have severe belly or side pain when they have a kidney stone. There are other benign causes of blood in the urine. After heavy exercise, one can see blood in the urine. Finally, occasionally blood in the urine appears once and then goes away. The cause of these episodes is frequently unknown. It is not possible to determine a diagnosis without an evaluation. Your primary care doctor or a urologist can help determine the cause of blood in the urine.