Insulin sensitivity as a fn of BG

[Eddy]

In

http://www.diabetesforums.com/forum/type-1-diabetes/25972-what-is-going-on.html#post306328

Bluesky made an interesting point about insulin resistance during elevated BG numbers. I _thought_ that insulin (and especially lispro) seemed to take longer to kick in when my BGs were high.

This morning, I awoke with BG of 82 mg/dL. :) I ate 4 U , covered with 3.5 U R (2h duration), added 1 U reg-N (to cover beginning of Lantus fade), and went back to sleep.

When I awoke 2h after eating, I felt as if I might be about to drop. Then I felt like I passed through 65... 60... into the 50s... so I checked. Sure enough, 52.

To get from 82 to 52 requires 1.2 U of excess. Yet I shorted myself 0.5 U. Even if the reg-N somehow finished insanely quickly, that wasn't _quite_ enough insulin to explain the drop.

Any other data, information, observations, insights?

And it was a food that I understand very well. Whole-grain raisin-cinnamon english muffins. BG usually remains constant when I cover with R.

[morrisma]

Eddy,
For me, this scenario sounds like you weren't at a steady 82 but at 82 and dropping. I get that from time to time when I do not have any idea of the rate my bg's are changing. For me it's the biggest push for cgms.

You were in an overnight situation so I'm not sure the mechanism needed to explain that! Let's see what others think.
Mike

[Eddy]

Eddy,
For me, this scenario sounds like you weren't at a steady 82 but at 82 and dropping. I get that from time to time when I do not have any idea of the rate my bg's are changing. For me it's the biggest push for cgms.


No, I'd be willing to bet that I was a stable 82. I'd have felt the drop while I prepped food. I _did_ feel myself dropping at the 2h postprandial mark; that's what awakened me the second time.

I've also had similar situations at other times of day. The other day I covered pizza (white flour) with insulin instead of lispro, and still went hypo. Mealtime BG was 60. (I was a bit late in eating, and Lantus stacking had caught up with me.)

Conversely, corrective boluses take _longer_ to kick in when I go over 200. That put me in a jam once when I unknowingly stacked an extra 4 U (worth 100 mg/dL drop) of lispro...

FWIW, my basal is pretty flat and easy to predict. Overnight drops _can_ happen when ambient air is cool enough, but last night's 68 deg-F (20 deg-C) is a temp that keeps me "on track".

[Eddy]

Quick addition:

Had I neither eaten nor bolused, I'd have climbed 15 mg/dL, presumably due to the beginning of Lantus fade. I ate and bolused at the 14h Lantus mark, where I consistently begin to climb a little. (The 1U reg-N combats the Lantus fade. At lunchtime, I use an extra 2U reg-N.)

This was just the most recent datapoint. I've noticed this at different times of day, with different foods, different insulins, etc.; the common factor is starting BG.

[Eddy]

Ehhhh.... I think this hypo may have been due to slower digestion. I'm now at 130, about 25 mg/dL than expected. That's roughly the balance....

But my question/curiosity still stands. If anyone has any observations correlating insulin sensitivity to BG at injection time, I'd love to hear more.

[Cyborg]

I know my insulin sensitivity is based on my current bg. If my bg gets anywhere near 200, it takes a lot of insulin to bring it back down. My ISF changes from about 20 to around 12 or less. The cozmo pump actually has supports a variable ISF based on bg.