On days when I don't drink a lot of liquid and I don't urinate as often, the next day or late that night when I do finally urinate there is a lot of blood in my urine. For the next 2 or 3 times I urinate, my urine is almost black in color with so much blood in it. After I drink enough liquids after a few urination it clears right back up. My doctor has treated me for a urinary track infection, thinking that was my problem. Is that correct and do I need to worry about something else?