Abstract: A sensor and method for measuring bilirubin in a liquid sample are disclosed. The sensor comprises a substrate comprising a reservoir disposed within the substrate, the reservoir having a top surface and a bottom surface; a filter; at least one transparent portion, the transparent portion forming at least a part of the bottom surface of the reservoir, and a reflector comprising at least a portion of the reservoir. The method for measuring bilirubin in a liquid sample comprises inserting a sensor into an analyzer; introducing the liquid sample to the sensor; filtering the liquid sample such that the sample flows into a reservoir in the sensor; illuminating the liquid sample in the sensor using a light source in the analyzer; measuring a reflectance of the liquid sample at one or more wavelengths using a detector in the analyzer; and computing a measurement of bilirubin using the measured reflectances.