Blood in the urine, also known as hematuria, occurs in 2.5 to 21 percent of individuals and is usually not a significant cause of alarm, according to the Urology Care Foundation. However, blood in the urine can also be a symptom of cancers, diseases, infections, injuries and urinary stones.
WebMD states that those who see blood in the urine should see a doctor immediately to rule out serious conditions. Because not all blood in urine is visible to the naked eye, it is important to visit a doctor if certain symptoms develop, such as pain while urinating, fever, chills, lower back pain, abdominal pain, pelvic pain, weakness or swelling. These are often signs of a bladder or kidney infection, kidney stones or kidney disease.