Math

I woke up Sunday night after being asleep for about 30 minutes. I didn't feel right, so I checked my BG. As I expected, it was low - 52. You might think, oh that's easy to fix, just eat some carbs and you're all good, and the general recommendation is to eat 15g of carb if you are low, then wait 15 minutes and test your BG again...

Well, it's not quite that simple, and after chatting about this on the phone with my mom, I realized that it's a good thing I'm a math major!

My Insulin: Carb ratio is about 1u:33pts right now, and my Insulin: BG ratio is between 1u:60g and 1u:80g. Thus, eating 10g of carb would raise my blood sugar about 20 points. My desired BG when I go to bed (and at most other times of the day) is 100, So if I had eaten 24g of carb, my BG would be right where it should be. Right? Not quite. I checked my pump to find out that I had .37 units of "Insulin on Board" which means that it is insulin from my last bolus that could still be used by my body. I also knew that I had some Insulin on board before I went to bed, so I set a temporary Basal rate at -90% for 1.5 hr. I checked my pump to find out that this had been active for .4 hr (note: my Basal rate is .5 unit/hr). So, sum it all up and figure out how many carbs should be eaten!

...No cheating!

Let's start with the basics - 24g of carb would work, considering nothing else. .37 units of Insulin on Board translates to about 12g of carb extra to be eaten. But, a -90% basal for .4 hr equals a .18 unit deficit of insulin (-6g carb), and 1.1 more hours at that rate equals another .495 (-16g carb) unit deficit.
So, that comes out to a grand total of 24 + 12 - 6 = 30g of carb to be eaten right at that moment, then I could have canceled the temp basal and been fine. Or, I could have eaten 30 - 16 = 14g of carb, kept the temp basal going, and it would have (hopefully) worked out eventually.

What did I do then? I thought about all this math for a couple minutes, figured the temp basal for .4hr would allow me to eat about 10g less carb than I needed to, and figured that the 1.1hr temp remaining would negate the .37u on board. So, I ate as many glucose tablets as I had near me, which happened to be 6. At 4g of carb per tablet, that comes out to a grand total of 24g of carb. Math is so much fun with a low blood sugar!

...My BG when I woke up was 160. Go Diabetes.