I feel really silly asking this question since we've had D and been pumping for a while but we have always used the refill cartridges for the pen. Because of billing or the pharmacy..I'm still not sure, we were sent regular vials this last shipment. My question is....when we used needles, we always pushed in the same amount of air as we were going to be filling up with insulin. Do we need to do this with the pump reservoir as well? I looked through 'Pumping Insulin' and can't seem to find the answer. Any help would be appreciated. Thanks.