Kidney disease
The kidneys are responsible for making the urine that gets stored in the bladder before excretion. If you have blood in your urine, it could be a sign that something is wrong with your kidneys. The kidneys filter waste materials from the blood while keeping blood cells out. If the interface where this activity happens becomes damaged or the efficiency drops due to disease, some blood may leak into the urine. This blood is what is observable as hematuria. At the earlier stages of kidney disease, the blood may be microscopic. With more severe damage, it may seriously tint the color of the urine.