Technologies are disclosed for a method and a device for detecting device colonization. Disclosed herein is an indwelling medical device configured to detect a biofilm. The device comprises a substrate configured to contact blood and a detecting material, disposed with the substrate, configured to detect the presence of a biofilm thereon. The detecting material is soluble in blood, removable by kidneys from the blood, and passable to urine by the kidneys for detection in the urine. A method for detecting the growth of a biofilm on an indwelling medical and a method for making an indwelling medical device are also disclosed herein.