Abstract: The invention concerns a method and a device for measuring an enzymatic activity in a body fluid. The method comprises the following steps: a) providing a support having a conductive surface whereon is immobilized a substrate specific of the enzymatic activity to be measured, the substrate comprising an electroactive residue; b) reacting a sample of the body fluid with the substrate so as to bring about an enzymatic reaction generating an electroactive product; c) detecting the amount of electroactive product by amperometric measurement using a support in contact with the medium containing the enzyme. The invention is useful in particular for measuring enzymatic activities related to blood coagulation.