A wearable device, comprising:
- a light source configured to emit light that is absorbed by blood glucose, the light source positioned on the wearable device to emit the light towards a body part of a subject as the subject wears the wearable device;
- an optical sensor configured to detect the light and positioned on the wearable device to detect reflected light passing through a vein or an artery of the subject;
- an impedance sensor configured to detect an impedance signal corresponding to an impedance of blood in the vein or the artery, the impedance sensor positioned in the wearable device adjacent to the optical sensor or the light source;
- a processing device coupled to the light source, the optical sensor, and the impedance sensor;
- and
- a memory device coupled to the processing device, the memory device storing instructions executable by the processing device to:
- determine, for a set of optical measurements taken during a measurement period, optical data based on the reflected light that is detected by the optical sensor, wherein the optical data indicates:
- a first set of blood glucose measurements;
- and
- optical noise that obscures the first set of blood glucose measurements;
- determine, for a set of impedance measurements taken during the measurement period, impedance data based on the impedance signal detected by the impedance sensor, wherein the impedance data indicates:
- a second set of blood glucose measurements;
- and
- impedance noise that obscures the second set of blood glucose measurements, wherein the impedance noise is non-correlative with the optical noise;
- generate, by a correlation function, combined data based on the optical data and the impedance data, wherein:
- the correlation function is a function of amplitude and time;
- the combined data indicates combined noise that is dampened relative to the optical noise and the impedance noise;
- and
- the combined data indicates a set of combined blood glucose measurements that are amplified or maintained relative to the first set of blood glucose measurements and the second set of blood glucose measurements;
- determine first average amplitude data for a first time segment of the combined data;
- determine second average amplitude data for a second time segment of the combined data;
- determine, based on the first average amplitude data and the second average amplitude data, change data that indicates a change in a blood glucose level of the subject;
- and
- output the change data to the memory device or another device in communication with the processing device.