Bolusing with IOB

When you eat and still have IOB, do you bolus using your current bg or just food?

Thanks for this question! Have never known what to do about IOB…also, if eating near a basal delivery, already know that my pump does not take that into account.

Me either. I am still trying to figure things out. I want to get rid of the lows.

My understanding is that with current pumps you take your blood sugar, enter your carb count and your pump will do the calculation. The computed bolus will combine a correction based on your blood sugar (subtracting IOB) and a meal bolus based on your carbs.

I think the IOB display is mostly for informational purposes. If you are low 2-3 hours after a meal and you still have IOB you want to know that you will probably be going even lower. But for the most part the pump should factor in IOB automagically into corrections (but it doesn’t affect the meal part of the bolus). I hope that makes sense and anyone with a better understanding can pipe in.


I have been on the pump for exactly 1 year and there are still sooooooooooo many questions. I am reading Pumping Insulin now.

Thank you, Brian_bsc.

And in case anyone wants further reading on general pump topics, John Walsh (of Pumping Insulin fame) has a great set of presentations on pumping at his website. One presentation in particular has a good explanation of IOB (he calls it Bolus on Board (BOB)) and differences between pumps.


I’ve been pumping for decades. I consider the IOB according to my plans for after the meal, how active I was during the day, AND my current bg. My pump has no idea what I am planning. If you want to use your pump to do all the figuring, just make sure all of your settings are in order.

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I am not afraid of insulin, so I do what newbies and others more “afraid” of insulin are instructed not to do: I stack insulin. I stack when I’ve gone way out of range and want to get my bg’s back down. Sometimes it’s incredibly difficult for me to get it back down, even with numerous boluses. Usually that happens from bad eating choices, but sometimes it seems to happen out of “the blue”. Right now, today, I’m switching eating habits to greatly reduce my carb consumption. that should stop me from having to stack. I hope I can stay on a carb-reduced diet. I did so about 3 years ago and quickly lost the exact number of pounds I wanted to,but I gradually put it on at the next thanksgiving/Christmas holidays.

I don’t recommend anyone else do what I do, as many people are very sensitive to insulin, and/or don’t feel their lows until they need assistance. Follow your doctors orders if things seem to go well, and if not, consider shopping for another doc. Consider a nutritionist also.

I’ve only been on my Ping for a couple weeks, but I have noticed that whenever I enter carbs to bolus for eating it never subtracts IOB from the suggested bolus for the food. It will, however, subtract from a suggested bolus for BG correction. For me, this answered a question I had about IOB for the 4 years I was on MDI. It never made sense to me to subtract IOB if the bolus was for actually eating more food. Of course, as @karen57 says, if I’m going to be active after a meal, then I’ll take that into account myself when deciding whether to follow the pump’s suggestion.

EDIT to add this is consistent with what @Brian_bsc says above.

when active after a meal I sometimes cut a bolus down by more than half. it depends on the timing of eating-to-activity start, projected length of activity as well as type, type of food, IOB, and intuition from having done this for a long, long time.

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Just food. The pump should incorporate the IOB when it calculates the bolus. If you already have enough on board it will recommend “0.00” as the amount. Pretty sure they all do this–one of the major advantages of using a pump in the first place.

Thank you, everyone.

In my experience, there is no clear answer to your question. Reading Pumping Insulin is a fabulous idea. There are excellent descriptions and examples to help you understand IOB and pumping and how to prevent stacking insulin, but still your own experiences combined with a solid understanding of what IOB is and how your pump calculates it and uses it will help you determine the best strategy.

There are instances where I would just bolus for food - like a second serving. Food hasn’t likely had time to impact my son’s blood sugar and any insulin that was recently delivered is intended for food consumed or a correction that still needs time to work. Subtracting IOB based upon a blood sugar at that time would likely result in not enough insulin for food eaten.

One and a half hours or longer after a meal bolus is when I start to pay attention to IOB, and allow the pump to subtract it from a subsequent bolus. However, my son and I also use our intuition based upon activity and current trends. It would not be uncommon for him to skip a bolus for carbs even if the pump calculated one based upon current IOB and carbs to be eaten if he’s being active. He’s a 12 year old who partakes in many sports, so this is a common consideration for us that the pump does not account for.

It’s important for you to know exactly how your pump is calculating IOB. They don’t all do it the same. Meal boluses and correction boluses aren’t always considered equally in the calculation. So even though the pump is doing the math, it’s important to know the equation and confirm mentally that it applies in whatever your current circumstance is.


Hi, @LorraineK (great name). What do you mean when you say your pump doesn’t take basal delivery into account? Are you referring to the IOB calculation? If you are, that’s correct. Pumps do not consider basal insulin in IOB. The presumption is that if basal rates are correct, that insulin is needed as a background insulin no matter what the circumstance, and that basal insulin is delivered around the clock, therefore eating would always happen near a basal delivery.

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Bolus insulin is for food, and correction insulin is just correction insulin. Each gram of carbs is covered by your I:C ratio and if your in your target range there is no added or subtracted insulin. If your BG is under your BG target when the calculation is made it may subtract some insulin or add if your over your BG target using the BG number you enter into pump. Again if your BG is stable you should not need to change your pump bolus recommendation, but since your pump has no idea if your BG is going up or down, it just uses the one entry to calculate a bolus, so if its dropping of climbing rapidly you may need to make a manual adjustment to the pumps bolus calculation…Basal insulin is just the insulin your body needs to sit at a idle…it has nothing to do with correcting or covering food…

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Hi Lorraine! So nice to finally meet :slight_smile: My basal settings occasionally run into a time when I eat. I have sensitivity to insulin (72) with a tendency to go low, and occasionally the basal delivery will cause a low if I am not paying attention (which can be often…haha). And so wonder if I should take that into account when a basal “drip” is going on when calculating for carbs. I have been told the basals are not factored into the calculator on my pump. Is that clearer?

I am not Lorraine but I can’t not ask…when does your basal NOT “drip”? The purpose of basal is to have insulin being delivered at all times. You should be able to skip a meal and your basal keeps you in range without any food or going low or any other type of worry. Basal is not calculated in the IOB but as said in the bolus answer, if you are getting lows from basal then you need to make some adjustments. Good luck.

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Thanks Karen. I do not have many basal settings because of my sensitivity. They are set based on diagnostics done and where I tended to go high (e.g., some dawn phenomena). And yes, continue to work on them, but am not being particularly “consistent” in my bg’s the past weeks making it more difficult to figure out. Thanks for the comment “not-lorraine” ha.

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Skip one meal each day to better figure out your correct basals. If you always eat 3 meals, you’ll never get the basals locked down. Basals have to be correct prior to working on I:C ratios and ISF.