Blood in the urine is also called hematuria. Normally, urine does not contain blood.

There are two kinds of hematuria:

  • Microscopic hematuria—Urine contains a small amount of blood, which is not visible to the naked eye
  • Gross hematuria—Urine is visibly discolored by blood, appearing red or tea-colored

In some cases, the cause of hematuria is never found. The list of known causes is lengthy. Some more common causes include: