Methods for manufacturing electrochemical sensors are described. The sensors have a working electrode and a counter electrode, which are planar, and optionally an indicator electrode. The sensor includes a sample chamber to hold a sample of no more than 1 .mu.L in electrolytic contact with the working electrode. The methods provide sensors that can be used to determine the concentration of a biomolecule, such as glucose or lactate, in a biological fluid, such as blood or serum, using techniques such as coulometry, amperometry, and potentiometry.