A quantum weak measurement scheme based on a Mach–Zehnder interferometer is proposed to detect the concentration of glucose, bringing this mechanism into the field of biomedical sensing for the first time, to the best of our knowledge. With a Mach–Zehnder interferometer system, we can analyze tiny phase differences between the two paths by measuring spectrum shift. We measured the concentration of glucose with weak measurement to achieve a concentration resolution of 8.98×10−5 g/L corresponding to a volume refractive index of 1.39×10−8 RIU, which was more than five times higher than the resolution achieved by conventional interference, 4.99×10−4 g/L. In the detection of glucose concentration in the blood serum of mice, a resolution of 1.0136×10−7 g/L for weak measurement was obtained.