Insulin duration?!

[Finn]

If "fast" acting insulin can still be influencing your blood sugar SIX hours after in had been injected, then what is the point of testing your blood sugar TWO hours after a meal? I understand that the effects of the bolus are winding down and there is no set time frame as to how long the insulin will offically be working because everyone is different. However, I would think the most accurate (blood sugar reading) information would be to test when the insulin is almost gone. That way you can judge the effects of most of the bolus instead of some of the bolus. Does that make sense? Am I missing something or have I just confused everyone? (perhaps I am just grumpy from low blood sugar)

[David]

However, I would think the most accurate (blood sugar reading) information would be to test when the insulin is almost gone. That way you can judge the effects of most of the bolus instead of some of the bolus.

While that may be true, having a high BGL for 2 hours and correcting is less damaging than being high for 4-6 hours and then correcting. It's better to keep BGs as level and close to normal as much as possible.

Conversely, catching lows early is important too.

Checking at two hours keeps me on track in a way impossible waiting until my next meal would be.

David

[seacomp]

If "fast" acting insulin can still be influencing your blood sugar SIX hours after in had been injected, then what is the point of testing your blood sugar TWO hours after a meal? The longest action time for Humalog or other rapid-acting insulin that I've seen is five hours and 85% or more is used up in three hours. Without getting into the math, the insulin functions on an expondentially decreasing curve.
The two hour mark represents, for most people, most of the time, the expected highest BG after a meal. Exactly when the highest BG is experienced depends on the composition of the meal, the amount of carbs, how fast they are absorbed, and similar factors and on exactly when the insulin was taken.
The remarks above about catching highs or lows early enough to do something about them is also relevant and correct.

[corwin]

Funny I wanted to ask the exact same thing. With my limited experience (only 2 weeks since I was diagnosed) I found out that if I really want to know how a meal effects my BG level I need to wait more then 2 hours. Most of the time I see a pretty big dif between 2 hours after a meal and 3-4 hours after.

I agree with David and seacomp about the reasons to check 2 hours after, however I think that if you really want to know how a meal effected you 3 hours reading will be more accurate. Please correct me if I'm wrong.

Cowrin.

[seacomp]

I think that if you really want to know how a meal effected you 3 hours reading will be more accurate. Please correct me if I'm wrong.

I think the question you are asking here is "What is the Net effect of a meal?" You want the net effect of a meal on your BG to be zero, which is what it is for a non-diabetic.
The amount of time to check for this depends on the meal and the medications, if any, that you are on. If you're not on meds and you have a meal of fast-acting carbs (high glycemic index), the net effect should be zero in 3 hours.
If your meal is more complex with long-acting carbs, meat and fat and you are taking insulin then 5 hours is more realistic.
"This is complex", you might say, "I have to know how everthing I eat affects my body, my blood glucose!"
Yes, if you are to manage your diabeties with any success.
But, it's not as bad as you might fear, over time, but not that long a time, you begin to get a "feel" for the various food and how they affect you. These calculations become almost second nature.

[Erin]

I'm not sure when we started being told to check our bg's at 2 hours after... Probably with the invent of Humalog / Novolog and the other really fast acting insulins. The theory is 2 hours post meal is the *Highest* your blood sugar will go, and as such, is the number you want to try to keep into a set range. (Many people say not to go over 140, but I find that QUITE a difficult goal to reach, I tend to be a bit more flexible) Back when we all used Regular, we had to *eat* 2 hours after each meal, because that's when R peaks.

While it is a good idea to check after each meal, the exact amount of time to wait is quite arbitrary. It's based on how the insulin is designed to work in an average body, but we're all different. If you find checking 3 hours later works better for you, do that. But as David and Seacomp said, it is better to be high for 2 hours rather than for 3.

[Shotokan]

Here's my 2 cents: The main reason was stated earlier: you want to keep your BS from being too high for an extended period.

How many times have you "guessed" the number of carbs in a meal and been wrong? How many times have you been perplexed that your BS is higher than it should be even when you "know" the number of carbs in a meal?

If you figure that, let's say 25 %, of the insulin you took for the meal is still active after 2 hours, then you can estimate whether that's enough insulin to get your BS into an acceptable range over the next 1 or 2 hours. In fact, you might still have undigested food running around, so it's possible that your BS would keep rising even more if the remaining insulin is inadequate to cover it.

However, if you do not have enough insulin remaining in your system at 2 hours, then you can inject enough at the 2 hour mark to bring your BS in line within the next 2 hours. If you wait 3 or 4 hours to test and correct, then you will have extended the time you have high BS by 1 or 2 hours. All these hours of high BS add up over time.