An infusion system that includes a controller device and a communication system to provide for two-way communication between the controller device and an infusion device that controls delivery of fluids to a user's body. Either the controller device or the infusion device may be integrated with a characteristic determining device in a single housing. The housing, in turn, may include a test-strip receptacle and an illuminator disposed so as to illuminate an area covering the receptacle and a test-strip inserted therein. The illuminator may be configured to be activated automatically when a test strip is inserted into the receptacle, selectively by the user via a button, key, or similar mechanism, and/or when the ambient light level, measured, e.g., with a light sensor, falls below a predetermined intensity. The illuminator may be a LED emitting white light, and may provide illumination at various levels of intensity.