Implantable device for measuring the glucose concentration of a body fluid when implanted, the device comprising a glucose measurement unit, the glucose measurement unit comprising a light source configured to emit light towards a light transmissive part of a housing of the device, the device further comprising an optical sensor configured to detect light returned through the transmissive part from the light source, and output an electrical signal based on the detected light, and a wireless communication module configured to wirelessly communicate with an external wireless communication device, wherein the wireless communication module is configured to wirelessly transmit a signal based on the electrical signal to the external wireless communication device.
