Presence of blood in urine may be due to:
1. Diseases of the kidney like glomerulonephritis
2. Medications like aspirin
, heparin, certain antibiotics, etc.
3. Vigorous exercise can also cause urine to have blood in it due to trauma to the bladder, breakdown of red blood cells, or dehydration
4. However urinary bleeding without pain may also indicate some serious disorder like cancer of the Urinary bladder
So...it will be better to consult an Urologist
to find out the exact cause.
Investigations like Urine examination & Ultrasound
scan of Abdomen & Pelvis will be helpful in clinching the diagnosis.
Wishing you a Good Health. Let me know if I need to clarify further.
Thanks & take care.