A substance concentration monitoring method comprising: inserting a temperature probe (1, 2) noninvasively into a healed piercing in a volume of a body in which a concentration of a substance is to be measured, the temperature probe (1, 2) contacting an internal surface of the volume and the substance being glucose; measuring an internal temperature of the volume as determined by heat transfer from the internal surface to the inserted temperature probe (1, 2) and producing an internal temperature signal indicative of the internal temperature; while the volume exhibits the internal temperature, directing an incident first near infrared, NIR, beam in a first wavelength band from a light source (4, 5) into a portion of the volume, the first wavelength band including a wavelength at which an absorption peak exists in a NIR absorption spectrum of the substance and the first NIR beam transmitting through the portion of the volume; while directing the incident first NIR beam, detecting an initial power of the incident first NIR beam and producing a first initial power signal indicative of the first initial power; while the volume exhibits the internal temperature, receiving the transmitted first NIR beam exiting from the portion of the volume onto a detector (6, 7); while receiving the exiting first NIR beam, detecting an exit power of the exiting first NIR beam not absorbed in the volume and producing a first material absorption signal indicative of the first exit power; while the volume exhibits the internal temperature, directing an incident second NIR beam in a second wavelength band from the light source (4, 5) into the portion of the volume, the substance exhibiting no absorption or negligible absorption in the second wavelength band and the second NIR beam transmitting through the portion of the volume; while directing the incident second NIR beam, detecting an initial power of the incident second NIR beam and producing a second initial power signal indicative of the second initial power; while the volume exhibits the internal temperature, receiving the transmitted second NIR beam exiting from the portion of the volume onto the detector (6, 7); while receiving the exiting second NIR beam, detecting an exit power of the exiting second NIR beam not absorbed in the volume and producing a second material absorption signal indicative of the second exit power; and calculating substance concentration in the portion of the volume based on values corresponding to the internal temperature signal, the first and second initial power signal, and the first and second material absorption signal. inserting a temperature probe (1, 2) noninvasively into a healed piercing in a volume of a body in which a concentration of a substance is to be measured, the temperature probe (1, 2) contacting an internal surface of the volume and the substance being glucose; measuring an internal temperature of the volume as determined by heat transfer from the internal surface to the inserted temperature probe (1, 2) and producing an internal temperature signal indicative of the internal temperature; while the volume exhibits the internal temperature, directing an incident first near infrared, NIR, beam in a first wavelength band from a light source (4, 5) into a portion of the volume, the first wavelength band including a wavelength at which an absorption peak exists in a NIR absorption spectrum of the substance and the first NIR beam transmitting through the portion of the volume; while directing the incident first NIR beam, detecting an initial power of the incident first NIR beam and producing a first initial power signal indicative of the first initial power; while the volume exhibits the internal temperature, receiving the transmitted first NIR beam exiting from the portion of the volume onto a detector (6, 7); while receiving the exiting first NIR beam, detecting an exit power of the exiting first NIR beam not absorbed in the volume and producing a first material absorption signal indicative of the first exit power; while the volume exhibits the internal temperature, directing an incident second NIR beam in a second wavelength band from the light source (4, 5) into the portion of the volume, the substance exhibiting no absorption or negligible absorption in the second wavelength band and the second NIR beam transmitting through the portion of the volume; while directing the incident second NIR beam, detecting an initial power of the incident second NIR beam and producing a second initial power signal indicative of the second initial power; while the volume exhibits the internal temperature, receiving the transmitted second NIR beam exiting from the portion of the volume onto the detector (6, 7); while receiving the exiting second NIR beam, detecting an exit power of the exiting second NIR beam not absorbed in the volume and producing a second material absorption signal indicative of the second exit power; and calculating substance concentration in the portion of the volume based on values corresponding to the internal temperature signal, the first and second initial power signal, and the first and second material absorption signal.