Combo Boluses and Corrections

Ok, I'm confused about something. Tonight I had a meal that I thought would need a combo bolus. I bolused 45/55 and 5 hours duration. Then I tested two hours after dinner and I was 213; yikes! I probably needed more up front. Anyway I went and dialed up BG bolus for a correction, taking into account the IOB. But then afterwards I thought about it and wondered if the IOB included the amount still waiting to be bolused in the remaining 3 hours. Probably not, huh? So I probably over-corrected. That's confusing! How are you supposed to know the right amount to correct? (I hope I explained that clearly)

That might be an Animas trainer question. It's a good one. That's where my CGM comes in handy, I can see where I am trending, is still going up or evening out. As an aside, the hardest thing for me on the combo bolus is the time frame part. I can pretty much guess the % for now and later, but the time frame. Who knows?

If you do find out from Animas - and I think they would know - please let us know.

Thanks, artwoman. I actually have changed the duration I use. I used to do three hours but then realized that for a high carb/high fat meal it's more like 5.

After my first response, I checked with my Think Like a Pancreas and Pumping Insulin books. They didn't really address the IOB beyond stating that it is calculated in the recommended dose. I don't know if there is a "secret formula" for the part two of a meal bolus (some math greek combination equation that I'll never figure out). John Walsh does have a "ask John" section on his website ( That would be a great place to pose your question.

What an idiot I am. I just realized that when I brought up the BG bolus to do the correction I could have looked at the IOB and then done the calculation to see if it was (as I suspect) just the amount that had already been delivered and not the anticipated amount to be delivered over the 5 hours. Duh! I didn't think about it until after I did the correction. If nobody knows off the top of their head I'll do that next time. I'm not a math geek but I can do that much of a calculation!

So I understand (cuz I am still tweaking the combo stuff) if you do a combo bolus you have say, 50% now and the other 50% 5 hours later for that highcarb/highfat meal? I was using only an hour. Sometimes that works, but other times I just try to remember to check in an hour (after part two of the bolus is delivered) to see if I need a correction.

No, my understanding of the combo bolus is that in that example it is 50% now and 50% spread out over 5 hours.

Thanks. I probably should re-read the owner's manual as well. Damn! it can be complicated. But doing it with a pump is a lot better than trying to figure out combo boluses and IOB with MDI.

I do 7 hours overnight. I put a higher percentage of insulin up front if I'm too high at bedtime. I use the ezbg correction amount as a starting point and then factor in the fat content (I eat a bowl of nuts at night, so I know my bg will creep up and I'll need more insulin later, rather than sooner.)

Do you know the answer about the combo bolus, etta amy; if the IOB includes the amount still to be delivered or just the amount already delivered?

Btw I just perused the manual under combo bolus, bg bolus and insulin on board and there is no answer to the question there.

I'll send John Walsh an email, asking him to come to this discussion. Perhaps he'll have an answer.

I just sent the email to Walsh. I had to guess at his email address at the Diabetes Mall (his website). Hopefully it went through.

I have noticed that when I do a combo bolus it keeps adding to the IOB as time passes & more of the dose is given. But I don't think it looks ahead to what is coming. On the other hand you probably need the full correction minus current IOB because that insulin to come will be needed for the rest of the meal as it is digested which is why you gave a combo bolus in the 1st place. Sorry that wasn't very clear I hope you understand what I'm trying to say.

Thank you, artwoman. I have never seen John Walsh actually participate in discussions here! But I do think Annabella's answer makes sense!

I agree that Annabella's answer makes a lot of sense. I 'spose if I were John Walsh, I'd participate under a pseudonym! You know, to maintain his personal life.


I've always thought that Endo's should lurk here to see what people with diabetes are concerned about - and to learn that there are those who do a good job and are pro-active. You've read enough of my postings to know the battles I've had getting respect for my experience with diabetes from healthcare providers.

Oh I absolutely agree. And it would make sense that they wouldn't identify themselves, even the non-famous ones because then people would be asking for free medical advice. Maybe that would be a good "test question" for a prospective doctor or endo: "How do you feel about your patients researching information on the internet?" I once actually asked that of a prospective new doctor and when she said "I like having educated clients" I immediately made an appointment. My "hmmmm..." was that I started wondering who he was posting as!

IOB only includes insulin actually delivered and not yet expired due to the duration of insulin action time. If a portion of the extended bolus is still pending then the pending amount is not part of the IOB. I do combo boluses everyday but avoid the confusing percentage split.

I always do a separate carb bolus for my carbs and then do an extended bolus for fat and protein with the percentage split at 0% now and 100% delivered over X.x hours. This split, on my terms, is easier for me to understand and troubleshoot later.

For me, doing corrections during the extended bolus period are more art than science. I look at the IOB and the amount of time of the extended bolus remaining. If my correction plays out while I am still awake, I can be more aggressive. If it's during the evening before bed, I might back off some. If I still want to be aggressive in the evening, then I'll set an alarm to check.

I have noticed that when I do a combo bolus it keeps adding to the IOB as time passes & more of the dose is given.

I've seen the same thing, Annabella.