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IOB When Snacking

PepperTed

PepperTed

Well-Known Member
Messages
104
Type of diabetes
Type 1
Treatment type
Pump
I'm quite confused about insulin on board. I had my lunch at 12pm and bolus'ed appropriately for it, plus a small correction as my BG was 8.1. I gave what the pump calculated.

Now it's almost 2pm and I'm eating an apple. I used the pump calculator which recommended 1 unit bolus for the apple, but then said I still have 3 units on board so advised no bolus. This doesn't seem right to me. The bolus I had is 'covering' the food I ate for lunch, so if I eat an apple and don't bolus again surely my BG will rise beyond target? Or does the pump somehow take that into account and has decided that I won't go over target from the apple? :S

I overrode the pump and gave myself 1 unit, so I'll wait and see what happens to my BG. I'm quite insulin resistant so 1u shouldn't send me into hypo. What would you have done?
 
when you tested your blood at snack time, you were obviously lower than your pump expected, and so the pump will assume that with 3 units still to go, you will drop even lower and likely below target, and that's why it doesn't give you anything.............

in a perfect world, when we test between meals, the correction we need should match the remaining IOB...........

I trust my pump...........if I was 6.3 mmol for example and still has 2 units to go, I wouldn't take insulin for a 20g bag of crisps.........

what was your BG reading before the snack?
 
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Thanks @novorapidboi26. I think you've shown me where I went wrong. I didn't test before the snack (after hourly testing for a few days, my arms are really sore) so I told the pump my BG was 6.5, my target, so that it wouldn't suggest a correction. As you say, that must have been lower than it was expecting.

I did test at 2:30pm and it had shot up to 16.9, so clearly my insulin:carb ratio is wrong at the moment!

I'll be honest with the pump in future :D
 
lol, I do this quite often too actually...........if I am having a snack not long after a main meal I will put in 5.5 as my reading so that it only gives me insulin for the carbs and not any more or less..........but that's within 1 hour of the meal when the meal dose is still reaching its peak....

the beauty of the pump is that it can work out an accurate dose for a snack because of the IOB, but it can sometimes catch a wrong dose too and compensate allowing you to be on target next meal....
 
Yes the dose correction was because of your relatively low reported BG, lower than expected, vs the IOB. The pump will never reduce a bolus dose due to IOB alone. It only reduces a bolus dose if you also provide a BG and the BG is low relative to IOB. In effect, if you provide a BG with a bolus dose, the pump calculates a correction dose and combines it with the bolus dose. The correction dose part may be negative, if BG is too low relative to IOB.
 
How clever our pumps are... I feel quite in awe of their maths skills :D
 
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