Thursday, July 18, 2013

Heat + Insulin = ??

I mentioned in my Gravenhurst race recap post on Monday that my blood sugars in the wee hours before the race were pretty horrific - hovering above 13 for hours and hours.

I changed my pump and popped in some fresh insulin and everything seemed to return to normal.

On Tuesday, we drove home from Gravenhurst after breakfast. I was feeling pretty rotten in the car so I checked my blood sugar. It was 20.4. Bah! I bolused and rechecked an hour later. 17.5. I repeated this cycle for a few hours and drank three huge bottles of water. I got it down to 10, took a double bolus for a protein bar because I was starving, ate it, and spiked again.

We got home, unpacked, did groceries and laundry and I fought to bring my blood sugar back under control again.

Then it dawned on me. We had spent most of Monday outside. In the shade and on a boat with the wind whipping by but still outside. It was 35 degrees.

Did I cook my insulin?

Sick on feeling high, I changed my site and my insulin for the second time in three days.  We had dinner and I settled nicely down to a more normal number.

There are lots of other logical reasons for my pre-race high (jitters being a big one). There are also other possible explanations for my Tuesday high. I hadn't exercised in three days. I was probably a little dehydrated after the day before.

Or both days of highs could have been caused from the heat wave we were in the middle of. Did I cook my insulin twice in four days simply by being outside?

The thing is that my insulin rarely, ever, does that. Even when I've done 2-3 training runs in the heat of summer, the insulin remained effective.

What's the difference this time?

I haven't changed the type of insulin I use but I have changed my pump.

Could different pumps be insulated differently? Do different pumps react differently to heat? It is the reservoir? Do they react differently in the heat?

I don't know but I will definitely be more vigilant as this heat wave continues. It's turned into a pretty expensive diabetes supply week.


  1. This has been happening to me, too, and it seems especially bad this summer, which has been very warm. I have yet to figure out why it happens, but I'm all but certain the heat has something to do with the highs that I've encountered over the last month. As with you, when I change sites and refill the insulin in the reservoir, I get back to "normal." By the end of the third day, it's crazy town again. I've started swapping insulin/infusion sets every 2-3 days, and that seems to help (even though it's super-annoying).

    I've also noticed via my CGM that my level of hydration is all over the place, which I'm sure has a role to play here, too. But I really think the insulin just becomes less potent the longer it's in the reservoir and tubing.

  2. Oh, we should also remember that heat is a form of stress. So it can cause higher blood glucose all by itself.