"Stacking" pre-meal insulin

I’ve been diabetic for about 8 months now and this has happened to me a couple of times.

A few times I’ve been eating dinner, after 2 units of insulin (for instance), and halfway through my meal, I realize that maybe I should have taken one more because I’ve done my carb math wrong. And it’s usually in a situation like “oh eff, my mom just got home from the holiday cookie exchange at work…damn!” or “WOW that def had potatoes in it. I’m totally gonna be high later,” or “that BBQ sauce tastes way too sweet…”

So…let’s say I take pre-meal (Humalog) of 2 or 3 units, and surprise, the dessert fairy arrives (or some other event that’s related to this delicious magnitude), can I take another unit while I’m still eating? Or shortly after?

Hermm…any advice is greatly appreciated.


Yes. I do it all the time. It’s a lot easier to do with a pump as it keeps track of active insulin and the duration, but it’s not all lost without one. Remember to account for what’s active and all when you’re checking two hours afterwards.


If I’m going to be eating more food than I originally thought (like if I decided half-way thru dinner that I want desert) I’ve always given more insulin (diabetic 18 years). If it’s something that I’m not sure about, like maybe my carbs are off, I’ll wait until afterwords and check again to see if I’m high and then correct for it. That way I don’t over bolus and go too low. And then I know for the next time that I eat that to give more insulin. Sometimes it’s just trial and error with some foods. maybe your body doesn’t process that carb like most would so maybe you need more or less insulin.

Sure, you can do this. It’s not really stacking insulin if you’re taking what’s needed to cover food. For something like dessert with carbs that hit quickly, don’t delay taking insulin. Of course, it’s all trial & error to learn what works best by testing.

You can definitely do that. That’s just carb dosing. It’s fine.

Yes. You need to or you’ll be high later. This isn’t really stacking.

Stacking is when you take a correction for a spike in your BG, not considering that you already have insulin in you from an earlier bolus or correction that is still working.

Yup, what Kari said. Boluses for carb-counting are generally administered independent of insulin on-board, whereas correction boluses must take it into account. When you start needing a calculator, that’s when you’re in trouble…

absolutely. ditto what Kari said.

Actually, if you are eating a slow digesting meal, perhaps something with lots of fat and protein (yum), then actually doing two injections can actually be a good way of covering the meal. In “Using Insulin” John Walsh gives the guidance that 20% of Humalog or Novolog is used in each hour after injection. I believe Walsh has been vocal that Insulin on Board (IOB) should be accounted for in both carb and correction bolues. I think a key problem with most current pumps is that they only account for IOB for correction. I take Regular, so it is even worse. So in the first hour, a second injection stacked on your first injection is the same as if you injected both at once (+/- 10%). That is pretty darn close, even for government work.

But as time goes on, like having dessert 2 hours after your first injection, I might actually test and then consider your insulin on board in figuring out the insulin needed to cover the dessert. At 2 hrs, you would still have 60% of your first insulin injection still on board and if you are back to 80 mg/dl you really should “subtract” that IOB from the carb bolus needed to cover the dessert. A stacking like this can lead to mandatory second desserts and it is best not to go there.

With most current pumps you would presumably be told to correct an 80 mg/dl at 2hrs (and 60% IOB) with some carbs. Why would these correction carbs not be factored into your carb bolus? I know that most pumps don’t do it this way, by Walsh thinks they should (see pg 43). Perhaps I don’t understand.

I know what bsc is saying. I think it’s really a matter of how you think about it. I’ll admit that, for better or worse, my thinking has adapted to MM’s bolus wizard over the last 6 years. That may be a big part of why I see IOB as a part of correction boluses, because that is the only time it comes into play.

In a situation where you don’t know the bg, as in the op, you simply bolus for the carbs and you’re done. You assume that any previous correction or carb bolus was correct because you don’t know otherwise. IOB doesn’t enter the equation, it’s just Bolus = Food.

When you know your bg, you add on correction and IOB adjustments. It becomes Bolus = Food + (Correction - IOB), where Correction can be + if you’re high or - if you’re low.

Because IOB only comes into play when a correction bolus (+ or -) is calculated, I always think of IOB as a modifier of the correction rather than a standalone component. But I guess that I don’t disagree with bsc either. In a mathematic sense, if you know your bg and it doesn’t require correction, then the equation just becomes Bolus = Food - IOB. But, like John said, this may or may not pan out. I’ll often adjust the final bolus in situations like this because IOB calculation is too imprecise and there are too many other factors that could affect the result.

I suppose if we all find what works for us, that is all that really matters. In my case, taking R, perhaps I need to worry more about the stacking. I openly admit to a certain absurd focus on having everything consistent. But I’ll probably need to take some care with my R and if I eat and bolus late afternoon, I probably should not ignore my IOB for my dinner carb bolus.

Please clarify stacking. Are stacking and IOB similar ? thanks
I’m still sort of new to this. If I bolused, let’s say 2 units, based on what my best “guesstimate” for a “mystery food” let’s say a croissant (guess 30 g carbs) , or some type of a bun, is being served to me and I could not measure it, and lets say two hours post meal, the BG is high around 200 and the Dexcom reads slow rising, not the double straight up fast rising, what’s the strategy for “correcting”? At two hours my 2 units of insulin has peaked and will be losing its effectiveness. If I bolus to correct the high, the correction won’t peak until 2 hours later. By then, wouldn’t the BG 200 have declined? Do most people correct “cautiously” (unless one knows definitely, that one under bolused due to miscalculations).

I tend to stack post meal bolus’s more than a pre-meal bolus. Now I cannot say I do it well, but I do it. I think the key is to use a cool head and test, test, test. The fat is a big factor in how I digest food.

best to all