Implantable device for measuring the glucose concentration of a body fluid when implanted, the implantable device comprising a glucose measurement unit, the glucose measurement unit comprising a first light source configured to emit light towards a light transmissive part of a housing of the device and a first optical sensor configured to detect light returned through the light transmissive part from the first light source, and output a first 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 first electrical signal to the external wireless communication device.
