Single-use electrical leads include a status flag element such as a fuse. The nerve stimulator has a "test mode" that determines a current value for treatment, and a "therapy mode" that administers treatment with the chosen current value. If the fuse in the electrical leads is blown, then the stimulator assumes that the leads have already been used and does not enter therapy mode, and optionally test mode. If the fuse in the electrical leads is intact, then the stimulator assumes that the leads are as yet unused, and allows the user to enter either test mode or therapy mode. The fuse is deliberately blown after a particular amount of time spent in therapy mode. After the fuse is blown, the user may still complete the therapy mode, even though the fuse is non-conducting. Preferably the fuse is electrically isolated from the leads that contact the patient.