It is normal for there to be a very small number of red blood cells in urine, according to MedlinePlus. However, the exact amount that counts as normal may differ, depending on the laboratory that performs the test.
A higher than normal red blood cell count in one's urine may be a symptom of a serious condition, such as a tumor or injury to the kidney, states MedlinePlus. Another common cause of blood in the urine is a bladder infection, as stated by WebMD. A bladder infection is usually accompanied by a burning sensation while urinating. Even though blood in the urine may not be a serious condition, patients should see a doctor to find the underlying cause.