A system for non-invasive measurement of a substance, such as glucose, includes a detector configured to sense radiation and an optical subsystem configured to focus the radiation on a sensitive area of the detector. The system includes one or more temperature sensors attached to one or more of a plurality of elements of the optical subsystem and to the detector and two or more temperature sensors configured to measure two or more respective ambient temperatures. The one or more temperature sensors are configured to measure the temperature of the one or more elements of the optical subsystem and the temperature of the detector. A method of measuring a concentration includes detecting an infrared radiation value, measuring the temperature of the detector, one or more components of the optical system, and two or more ambient temperatures, and correlating the temperatures with calibration parameters to correct the detected infrared radiation value.