In some implementations, an apparatus includes a physiological light monitoring subsystem that includes a source-detector assembly having a first side that has three transmitters of electromagnetic radiation frequencies in ranges of 375-415 nm, 640-680 nm and 920-960 nm frequencies and a first photodiode receiver of electromagnetic radiation in a 350-1100 nm range to measure an amount of electromagnetic radiation that is reflected by a subject, a microprocessor configured to determine an indication of an amount of glucose in the subject calculated from a ratio of electromagnetic radiation received by a first photodiode receiver of electromagnetic radiation in the 350-1100 nm range to measure an amount of electromagnetic radiation that is absorbed by the subject at the 375-415 nm frequency range in comparison to electromagnetic radiation received at the 920-960 nm frequency range, the subject being positioned between the first side and a second side.
