Monday, September 16, 2013

IOB - It Actually Does Make a Difference

I really like a lot of things about insulin pumps.

I love some of them.

I really really love Insulin on Board. It's one of those things that doesn't just claim to make my life easier...

like this handy-dandy spaghetti measurer / pasta scooper / cheese grater actually does.

Insulin lasts in the body for a certain amount of time. It varies with the type of insulin, the person and, because we're talking about diabetes, a million other variables including the number of dragons flying overhead, the weather, who won Le Tour de France and the number of children Brangelina have.

For me, Humalog (the insulin I use in my pump) typically lasts about three hours in my system. So if I take six units at noon, I will (theoretically) have four units left by 1pm, two units by 2pm and my lunch bolus should be out of my system by 3pm.

Insulin on Board refers to the amount of insulin left in my system and Lucky, my pump, calculates it for me.

"This is great because...?" you ask.

Well, here is one example. Let's pretend that I had lunch at noon and bolused for it. Two hours later, I'm 9.0. Nine is a high number that, normally, I wouldn't want to see. So I'll tell Lucky that my blood sugar is 9.0. Lucky will do his math thing and he might tell me that I should take 1.5 units of insulin to correct the high.

But wait!! Lucky says. You have 1.5 units of insulin on board from lunch so you don't need to take anything.

Before my pump I used to have to remember how much insulin I took with my lunch, do some math in my head to figure out how much I'd need to bring my BG down from 9.0, guesstimate out whether I had that amount left in my system, hope that Brangelina hadn't adopted any children over the weekend and bolus accordingly.

Last weekend Doug and I had a busy Saturday. We ran 10k in the morning, had breakfast, showered and then hopped in the car for a 2-hour drive to a family event. My blood sugar was high when I woke up but it dropped nicely down to 7.2 after my run. I bolused for breakfast (minus a bit because I had just run) and then I changed my pump. I also changed my battery since it was getting low. I showered and we left.

About 30 minutes into our drive, I felt pretty awful. A quick BG check showed that I was 15.5. My pump told me that I needed 2.5 units to correct the high so I took it.

Right after the insulin was delivered, my brain said "but what about insulin on board?".


Lucky said that I didn't have any but I had taken five units with breakfast only 1 1/2 hours earlier. So I should still have almost 3 units lefts. I double checked that I actually did bolus for breakfast (I did). I double-checked my insulin on board. The bolus I just took was there but nothing from breakfast.

That's scary.

I tried to figure out what might have happened. I haven't changed any settings on my pump. But I did change my battery. Is that it? Does changing a battery wipe out recent IOB memory? If so, that's a little disconcerting.

As it so happens, my BG was really high all day so the extra bolus I accidentally took didn't do much damage but it could have.

I'll have to be attentive the next time I change the battery to see if it happens again.

If so, I'm thinking I need to have a chat with Animas to let them know.


  1. When I did my training for the Animas Pump they did tell me that when changing the battery the IOB would go back to zero. This is definitely one thing they need to work on!

  2. Hmm I didn't even think about how changing the battery could delete my IOB far it hasn't caused a problem but I will need to start paying attention more!