Why is there blood in my urine?

Overview
It can be scary to see blood in urine, also called hematuria. In many cases, the cause is harmless. But blood in urine also can be a sign of a serious illness.

If you can see the blood, it's called gross hematuria. Blood that can't be seen with the naked eye is called microscopic hematuria. It's such a small amount that it can be seen only under a microscope when a lab tests the urine. Either way, it's important to figure out the reason for the bleeding.

Treatment depends on the cause.

Source and all the information you need:
https://www.drugs.com/health-guide/hematuria.html