A device includes an optical circuit that obtains a first signal at a first wavelength using light reflected from skin tissue of a patient, wherein the first wavelength has a high absorption coefficient for nitric oxide (NO) in blood flow and a second PPG signal at a second wavelength using light reflected from skin tissue of the patient, wherein the second wavelength has a low absorption coefficient for NO in blood flow. A measurement of a level of NO in blood flow is determined using the first PPG signal and the second PPG signal. A health condition is determined using the measurement of the level of NO, such as hyperglycemia or hypoglycemia.
