Blood in the urine can occur due to a urinary tract infection, kidney infection, kidney stone or bladder stone, according to Mayo Clinic. Other potential causes of blood in the urine are kidney disease, an enlarged prostate and cancer.
An injury to the kidney can also cause blood in the urine, says Mayo Clinic. Genetic disorders such as sickle cell anemia and Alport syndrome also cause the condition. Sometimes, drugs such as Cytoxan, penicillin and blood thinners cause blood in the urine, as can strenuous exercise. Whatever the cause, a person should seek medical attention immediately if he sees blood in his urine.