I am sorry to hear you are worried about your cat. My name is Rebecca. I am a veterinarian and will do my best to help.
Blood in the urine can be caused by more than one condition in cats. It might be a bacterial infection and need antibiotics. Sometimes it means that there is sand or crystals or stones in the bladder. These can sometimes be dissolved by special diets, but sometimes stones have to be surgically removed.
There is a condition in male cats that is serious. If they form crystals in the urine, sometime the crystals form a plug that causes a blockage in the urethra, and the cat can't pass urine. This is an emergency; a cat can only go a day or so without urinating before they go into kidney failure. As long as he is passing urine, even bloody urine, this is not a problem (or if your cat is female it is not a problem).
Sometimes cats get "sterile cystitis", blood in the urine but no infection. They are uncomfortable and medication helps. We do not know the cause of cats getting this condition, but it can be helped with special diet.
The best place to start is with a urinalysis, to find out if there is an infection, and if your cat needs antibiotics or if there are crystals in the urine.
Let me know what else I can help with or answer. Rebecca