It is our turn to report on our expired insulin experiment. We focused on evaluating what happens to insulin that has been opened, then left in the fridge.
We opened a Novolog insulin pen in August 2016, used it once, and left it ouf of the fridge for a week. We have left it in the fridge ever since. About once a month (very approximately), we have taken it out of the fridge, brought it to room temperature for a few minutes, then put it back in the fridge.
Yesterday we experimented with it. What we found:
The plunger had a little bit of initial friction. We had a hard time getting it going. For a few seconds, we even thought it was actually frozen.
We were able to inject after about one minute of experimentation. The insulin (a 6-unit dose) was effective, although my son went a touch high. it could well be due to his being a bit sick right now – or it could be that the insulin has lost a bit of efficiency. But – what is clear is that it still works.
We will continue experimenting with it over the next few weeks/months, and report.
[EDIT] added the first week out of the fridge which I had forgotten to mention.