Proper insertion of medical leads into medical devices is detected at the time the lead is being inserted. An external device initiates impedance testing by the medical device that is receiving the lead prior to the insertion of the lead being completed. The medical device reports back the results of the impedance testing so that the external device can determine whether the lead is properly inserted at the time of lead insertion and can provide an output to a user to indicate whether the lead insertion is proper. The medical device may poll only a last connector expected to be connected before responding, test other connector combinations before or after responding, and so forth.