We present a case of pyelonephritis following the extended andsolitary use of over-the-counter phenazopyridine in a forty-year-oldfemale. The patient initially had uncomplicated cystitis signs andsymptoms which partially resolved with phenazopyridine and therefore she continued use. She presented to the emergency department with systemicsigns and symptoms of acute pyelonephritis. As phenazopyridine is devoidof antibacterial properties this allowed the lower urinary tractinfection to progress to acute pyelonephritis requiring intravenousantibiotics. Better patient education may preclude this complication.