A glucose sensor for intravascular measurement of glucose concentration wherein the sensor is arranged to measure glucose concentration by monitoring the lifetime of the fluorophore, the sensor comprising:—an indicator system comprising a receptor for selectively binding to glucose and a fluorophore associated with said receptor, wherein the fluorophore has a life-time of less than 100 ns—a light source—an optical fibre arranged to direct light from the light source onto the indicator system —a detector arranged to receive fluorescent light emitted from the indicator system and—a signal processor arranged to determine information related to a fluorescence lifetime of the fluorophore based on at least the output signal of the detector.
