As a type 2, you may observe different action profiles for corrections than a T1 might see. The reason? You still produce some insulin. The injected insulin "helps" but is not enough to fully do the job of bringing your blood sugar down. Instead you are depending on your natural insulin production for the last part of the action to bring your blood sugar down.
The solution? A larger novolog injection. This is accomplished by making appropriate adjustments to you Correction Factor (sometimes called Insulin Sensitivity Factor). You can consult with a CDE or your doctor for help doing this if you don't know how to do it.
ps. The same sort of observation may also occur with T1s who have improper settings for their insulin regime where their basal is partly covering meals.
What I am saying is that for a T2, they may still produce some insulin, just not enough. So if you are hyperglycemic after a meal, without insulin, your blood sugar will just slowly drop over a period of hours. If you add on a correction, it may bring your blood sugar down "some," but unless you take a big enough correction your blood sugar will still be high after 3 hours. At this point, your natural insulin production still continues to slowly drop your blood sugar.
Did I explain it any better?
It sounds like your corrective insulin doses are working. Novolog, like all the fast acting insulins, is rated in terms of onset, peak, and duration. According to Novo Nordisk's website, its onset is 10-20 minutes, it peaks in 40-50 minutes, and its duration is 3-5 hours. That being said, everyone has a unique metabolism and your times will vary somewhat from this. In fact, the insulin action will probably vary a bit each time you take it, depending on the time of day and a variety of personal factor.
If you're like me you want to bring down high blood glucose numbers as quickly as possible. Unfortunately, Novolog is one of the fastest insulins available today. If your BG returns to the normal range in 4-5 hours then your corrective dose is working. I know that seems like forever when you're high but that's the current state of the art with today's fast acting insulins.
If I want my BG to respond as soon as possible to a correction dose then I try to go out for a 30 minute walk when the insulin peaks at 40-50 minutes after dosing. That's one of the few things that I know helps speed things up. I hope this helps.
I'm a T1 but when my blood glucose is high I become more resistant to insulin and it can take several hours before my BGs drop. As a T2 you already have insulin resistance going against you. Adding more insulin won't make it drop faster and might increase that resistance.
That makes sense--a couple of week ago (when I was still on 1/3 for adjustments) my BG went to 580 (for no reason!) and I took 154 units of novolog. It took over 3 hours just to get it down to 300. I was scared to try walking at that high a number so I just drank a lot of water. The next day it dropped from 219 to 73 in 2 hours without taking any insulin (and not eating).
My old endo had told me "if it's too slow, then just increase your dosage"--clearly that didn't work (hence the dose of 154).
What happens if you get totally insulin resistant?
Well, this is different. A large bolus is absorbed more slowly. The size of the bolus is the volume, but the absorption surface is basically the surface of the bubble of insulin, namely the area. Thus a large bolus absorbs more slowly. It is for this reason that Bernstein recommends only injecting 7 units at once and that syringes only come in 50 unit barrels.
Should you need to do large corrections, you may find it works better to use a syringe and break the injection up into a number of smaller injections.
Also, remember you don't know where you're catching the bg curve when you dose. If you check your blood sugar and it's high, it could be that it's still climbing from a previous meal--some foods take longer to digest. You take your insulin, and it starts working . . . but your blood sugar is still climbing too, so the net result is that your bg number remains the same for a time before the blood sugar stops entering your system, and the insulin starts working to bring it down.
I'm on a Dexcom 7 CGM so I can see if it's still climbing or not. (although it only diplays numbers up to 400, it still shows the arrows to indicate direction of change)
Another contributing factor is if you have any food in your stomach that you're still digesting that is continuing to push your bg higher.
You didn't say if this was a "wake-up" high situation, which would be very much different than if you tested 90 minutes after a large meal and were way out of range.
Great responses here - that's one of the things I love about TD!!!!
It was three hours after eating a small meal.
Looks like I'll have to continue keeping detailed records to determine what the other factors are that affect my response to insulin (because sometimes it DOES work fast).
what is TDD?
TDD is your total daily dose. It looks like you have some serious insulin resistance going on there. I would be interested in knowing what your last meal consisted of. If it was high in fat then the fat might be slowing the digestion of the carbs and thus your carbs are still with you for a while but that's just a shot in the dark.
Insulin resistance is one of the hardest thing to deal with for T2's. My doses have been pretty high in the past but not quite as high as yours. My solution was to limit the carbs that I eat. I have managed to lower how much insulin I need but it is still much higher than your average T1. My TDD now is 60 to 80 units but has been as high as 250.