Hematuria refers to the presence of blood in the urine.   Two types of blood can exist in the urine, visible or invisible blood.  Blood which can be seen in the urine is referred to as gross hematuria, while blood which can only be seen with a microscope is called microscopic hematuria. In hematuria, one or various parts of your urinary tract, which includes the kidneys, urethra and bladder, allow blood cells to leak into urine. While this symptom is not necessarily something to worry about, in some cases it does point to more serious conditions. Hematuria can have symptoms like pain, blood clots, red tinged urine, or you could be asymptomatic. Because the causes of hematuria vary so greatly, paying close attention to symptoms if they arise is key.