A contact lens having an integrated glucose sensor is provided. The contact lens includes an electrochemical sensor configured to measure the level of glucose in the tear fluid of the eye of the user wearing the contact lens. The electrochemical sensor is powered by radiation off-lens, through an RF antenna or a photovoltaic device mounted on the periphery of the contact lens. The power provided to the contact lens also enables transmission of data from the electrochemical sensor, for example by backscatter communications or optically by an LED mounted to the lens.