Kidney infections, injury to the back, kidney and urinary stones, urinary tract infections, tumors, and sexually transmitted diseases. You have to go to a doctor, because only then can they determine where the blood is actually coming from. It's probably fine, and all of these things can be taken care of. Good luck!
blood in the urine means something is going on within your urinary tract. the amount of blood seen isn't supposed to be indicative of the seriousness of the issue. It could be from a small blood vessle, inflammation, infection, something in the prostrate gland, or the least likely, tumor. whatever the reason, you need to be evaluated. from what the urologist told me, while cancer is the least likely reason someone sees blood in their urine, it always merits a doctor's visit. i just went through this, and it was pretty scary. all okay here, tho, and you probably will be, too :)