One of the modern ways to diagnose diseases is through exhale gas of patients, which is non-invasive and therefore desirable to doctors. The composition of exhaled breath contains valuable information for identifying hyperbilirubinemia disease. The accumulation of bilirubin and its lack of excretion causes jaundice, and the production of bilirubin has a direct relationship with exhaled carbon monoxide (CO). A CO diagnostic sensor based on a photonic crystal fiber (PCF) that can detect hyperbilirubinemia has been designed. This method can be used repeatedly to detect and treated jaundice in time. The PCF is designed as a hexagon. The holes in the cladding are circular and the holes in the core are circular and oval. Finite element method is used to do all the numerical simulations. COMSOL Multiphysics software was used to obtain the results. In this setup, CO absorption wavelength is 1.567 μm, and the relative sensitivity of 64.28% is reported with confinement loss of 3.81 × 10 ^{− 3} dB / m.