A biosensor for monitoring nitric oxide (NO) of a patient in vivo, includes a PPG circuit configured to obtain a first spectral response for light reflected at a first wavelength from skin tissue of the patient, wherein the first wavelength has a high absorption coefficient for nitric oxide in arterial blood flow and obtain a second spectral response for light reflected at a second wavelength from skin tissue of the patient, wherein the second wavelength has a low absorption coefficient for nitric oxide in arterial blood flow. The biosensor further includes a processing circuit configured to determine an NO measurement value for nitric oxide using the first spectral response and the second spectral response and obtain an adjusted measurement value of nitric oxide by compensating the NO measurement value using a measurement value for at least a first species of hemoglobin.