The Omnipod insulin pump deploys the canula for delivering the insulin under the skin by way of a needle that inserts the plastic canula and then retracts, leaving the flexible canula inserted. Very infrequently, the needle will fail to retract. In three years of usage, I think my son had this happen perhaps two or three times. That's over 500 insertions for him, but only a handful of failures.
It is, however, helpful to know when this has happened. The first clue for my son is that it is painful. The needle isn't flexible, so it is felt on movement of that insertion site. Looking in the view window of the pod didn't help me, as the needle would be inside the canula and not visible. So how to know if this has happened?
We look at the "pink slide". If the needle has inserted the canula and successfully retracted, there will be a pink rectangle at the bottom of the yellow circle on the right.
The pink slide is the best way to know if the needle retracted or did not deploy the canula at all. Upon deactivating and removing the pod, we would find that in a failed insertion the needle was still inside the canula and sharp to the touch (be careful!). Another way to know that it has deployed is that once you start the insertion process, you'll hear a series of softer clicks and one louder, stronger click from the insertion.
Anytime the needle fails to retract, it is important to report it to Omnipod customer service as the feedback helps improve the product. They should replace the pod for you. A photo of the pink slide is available on Insulet's website also.
For my son, this pump is the only pump as he said "no tubes". Any pump will have a problem now and again, but the extreme benefits for us outweigh the cons.
Again, this is based on our own anecdotal and personal experience. If you have any questions, please contact your doctor or Insulet Omnipod.