An infusion pump system includes a removable in vivo glucose sensor for monitoring glucose concentration level in a patient, and for signaling an infusion pump to deliver a selected medication such as insulin to a patient. The glucose sensor comprises a sensor cable for placement through a catheter to position a distal sensor tip at a selected in vivo sensor site. A proximal end of the sensor cable seats within a connector fitting mounted on the catheter at a convenient and accessible subcutaneous position. The connector fitting couples the sensor cable to an implanted control unit which signals the infusion pump to deliver the patient medication. In a preferred system, the infusion pump is also implanted and receives control signals via a direct or telemetric connection. The sensor cable is easily accessed at the connector fitting for periodic sensor removal and replacement, without requiring removal or replacement of other system components.