The most common cause of painful blood in urine in female patients is urinary tract infection, which causes symptoms such as frequent urination, urgent urination, painful urination, incomplete urination, and blood in the eyes. If the infection goes upstream and causes acute pyelonephritis, it will also be accompanied by generalized fever and chills, and the diagnosis should be made by routine blood and urine tests at the hospital. Another thing that needs to be ruled out is painful urination caused by urinary stones, accompanied by visual or microscopic hematuria, so you can go to the hospital to have an ultrasound of the urinary tract to clarify the diagnosis.