Insulin usage time:carbs

[barrym]

Hi

I've been a T1 (or 1.5) for 8 years and have a pretty good handle on my diabetes and control it fairly well but still get very annoyed when things don't go as predicted. So that's pretty much every day what with dawn phenomenon and actual carbs being different to what I think. Anyway I have a fairly basic misunderstanding of one aspect and that is insulin time profile.

I'll try and describe a theoretical scenario to demonstrate.

I use 1 unit to 10g of carbs.

I'm at 5.5 mmol and about to eat a sandwich of 20g. So I inject 2 units.

In theory the insulin can remain in my system for 4 hours. Does this mean that if it processes the carbs in two hours I have none left and won't go any lower than where I started, or is the insulin active for 4 hours?

Does it last in your system as per the manufacturers profile at a maximum performance for the 4 hours, or does it get used in full by the carbs in what ever time it takes to do that?

I hope I explained that question OK. It's been confusing me for some time. I use mySugr and rely on its "Insulin on Board" and requirement calculator all the time, but I think I may be too trusting of it.

Looking forward to lots of answers;-)

 

[barrym]

Hmm, may not be such a straight forward question. Just had a read of this .

 

[Seacrow]

OK, this is my understanding.
If the insulin profile peaks at two hours and tails off (goes to zero) at four hours -
- there is insulin taking glucose from the blood for the entire four hours
- two hours is the point at which most insulin is being used, so this is the time when glucose is being taken fastest from the blood and probably when your bg measurement is changing most rapidly
- at or around two hours (since the profile peak is not symmetrical) just over half the insulin dose has been used.

Does this help any?

 

[barrym]

Yes that does help, but I'm still a bit unclear about the relationship between that and amount of glucose. In my example, if I had a sandwich of 40g and took just 2 units when would I run out of insulin, at 2hrs or 4hrs, but presumably with the same raised BG.

I think looking at the paper I linked above, I'm over simplifying the question.