Insulin on Board calculation with pump

Hi there

Our 8 year old boy has been pumping for about 3 months now. One thing I feel might need adjustment is his insulin on board setting. At the moment the setting is at 4 hours but a couple of things seem to indicate it could be a little shorter

1. After using a CGM we can clearly see how long corrections take to complete their adjustment ( night time corrections while fasting)

2. Sometimes the insulin stacking calculation as part of the wizard feature does not allow enough insulin to be used to make an adjustment.

My question to everyone is What time setting are you using ? and if if you did change the setting what indicators did you use ? and how did the changes go ?

many thanks


Hi Felix, in case of my 13 year old boy we finally decided to set the pump IoB time as 3 hours. This is to use a very prudential approach. Still we believe that for about 80% of the cases the real IoB time is shorter (about 2 or 2.5 hours at most). What we have noticed is that the action of a single bolus is longer when the basal rate is lower: in a sense, when the basal rate is really well adjusted, and not too low, then the real IoB time doesn't exceed 2 hours.

Of course, this is just our singular experience.

The leaflet that comes with the insulin that you purchase for the pump will give you detailed information.

Our son uses Novorapid. Action start is 15 minutes, peak 45 to 90 minutes and duration is 3 - 5 hours. All aspects from start to finish will vary from individual to individual and will also vary with blood flow, site absorption, temperature and exercise.

That being said, we use an active insulin setting in our son's pump, in between the 3 - 5 hour suggestion. His pump active insulin time is set at 4 hours.

We use 3 hours also right now, but I really prefer to use 2.5. We were dealing with a couple of lows so backed off from 2.5 a bit. I truly don't think this setting was causing the lows, but we wanted to remove any factor that might be contributing.

I use the 4-hour setting for my son's pump (he's on Humalog) and it seems to work for us. There've been a couple times recently that we had site failures happen within 3-4 hours of an insulin dose and we saw no ketones, which is a pretty good sign insulin is working in the body to deliver glucose into the cells, even if it's not clearing all of it out. I think the last one, on Monday, I took a blood ketone reading about 2 hours after setting a site that turned out to be bad, and it was 0.1—he had had his last insulin bolus at ~8:30, and I took the reading at 12:30. His blood sugars were climbing, but we didn't see ketones until afternoon. So I think the 4-hour window is about right for us.

We have ours set at 2 hours. I know, I know...but it works for us. I know, from numerous finger pricks, that I really don't see much of a drop after 2 hours in her BG post correction. I would use the CGM to see how long corrections take during the day AND at night (because it will differ) and then use your son's own body to set the insulin duration based on that. Trial and error, trial and error...but 4 hours seems a wee bit long. Maybe try 3 and see how it goes.

Our sons pump is set on 3.5 hours requested by his endo. I think it is more like 4 because anytime I bolus in less than 4 he tends to fall low. She argues and wants it changed each time we visit.

Hi Riccardo Thanks for message. I brought the IOB down about two weeks ago from 4 to 3 and so far so good. I will watch out for possible shorter IOB when we nail the basal's

Hi Cheryl

Thanks very much for message. I reduced the IOB about three weeks ago to 3 hours and it seems to have helped so far best regards