The invention concerns a control device for a medical test system which has a lancing element that can be inserted into body tissue to collect body fluid and a lancing drive for the lancing element. A sensor element for body fluid is arranged on the lancing element and a control unit is coupled to the sensor element for detecting a fault when collecting body fluid. In order to improve the success rate, the control unit actuates the lancing drive for an automatic puncture repetition in less than 1 second when a fault, e.g., inadequate wetting of a detection field, occurs.