We present a MEMS sensor aiming to enable continuous monitoring of glucose levels in diabetes patients. The device features a magnetically-driven vibrating microcantilever, which is situated in a microchamber and separated from the environment by a semi-permeable membrane. Glucose sensing is based on affinity binding principles using a solution of dextran concanavalin-A (Con A) as the sensing fluid. The glucose concentration is determined by detecting viscosity changes induced by the binding of glucose to Con A through the measurement of the cantilever's vibration parameters. The device is capable of measuring physiologically relevant glucose concentrations from 0 to 25 mM with a resolution better than 0.025 mM and a phase sensitivity better than 0.4° mM-1. The response of the sensor to glucose concentration changes has a time constant down to 4.27 min, and can be further improved with optimized device designs.