I'm a little frustrated and at the same time, wondering if I am completely wrong about my son's pump not working as it should. He had his first pump a little over a year. His numbers became so bazaar. Then, I discovered that a correction by his pump would not bring his numbers down, but a simple injection did....multiple times. So, in my mind it clearly was the pump. Medtronic did the series of testing with me over the phone and replaced the pump. Basically the testing consists of you clamping off the tubing and "filling the cannula" with 10 units of insulin instead of the normal .3 or so. Supposedly, the pump is designed to sense the build up of pressure which causes a "NO DELIVERY" alarm. I knew this when I got the second pump and tested it myself before he used it. When we first got it, we got the "NO DELIVERY" alarm after about 1.5 units so I figured the second pump was fine at that point. Fast forward about a year with our second pump and my son's numbers have been doing the same thing. This time, when I called Medtronic, through the series of testing they determined it was functioning as it should. It took the pump failing to deliver 9.8 units of insulin before we got a "NO DELIVERY" alarm. It is scary to me that for example, my son could bolus with 5 units of insulin, the pump may fail to administer the insulin (resulting in extreme highs) and then out of no where..release it without warning (resulting in extreme lows). Am I crazy or has anyone else struggled with this? Medtronic is sending a replacement, but doesn't seem too happy about it. Of course, I don't really care what they think when it comes to my son's safety, but I don't like feeling guilty either.