A biosensor that includes working and counter electrodes of substantially the same size and made of the same electrically conducting material. A reagent is contained in a reagent well in the biosensor. The reagent includes a redox mediator, an enzyme, and a buffer, and covers substantially equal surface areas of portions of the working and counter electrodes. When a sample, containing the analyte to be measured, is added to the reagent well, a reaction occurs that oxidizes the analyte and reduces the redox mediator. After this reaction is complete, an electrical potential difference is applied between the electrodes. The amount of oxidized form of the redox mediator at the counter electrode and the applied potential difference must be sufficient to cause diffusion limited electrooxidation of the reduced form of the redox mediator at the surface of the working electrode. After a short time delay, current produced by the electrooxidation of the reduced form of the redox mediator is measured and the observed current is correlated to the amount of the analyte in the sample. In some cases, the analyte sought to be measured may be reduced and the redox mediator may be oxidized. In such cases, current produced by diffusion limited electroreduction of the oxidized form of the redox mediator is measured and correlated to the amount of analyte in the sample.