What is the formula for calculating lows?

[Loweryclan]

Ok, leave it up to a 'too smart for his own good' 9yo to have me stumped doing mathematical equations tonight, LOL So, I give up and turn to you for answers.

Connor asked me the simple question of how does the pump know how much insulin to give him for a meal when he is low. If he is low before a meal or a big snack, we tell the pump to do a correction and it adjusts for the low, but what is the formula?

Ok, use these facts.

Carb to Insulin Ration 1:15
Correction Factor 90
Target BG - 120

Hypothetical Situation
BS 90
Carbs 60grams

What would the dosage be?

[Eoin'sMam]

Ok this is what I reckon...but could be wrong..trying to get this into english is the challenge...but here goes

His intake is 60 so divide 60 by 15 to get what he normally should have of 4

He is 90 but needs to be 120 so he needs to increase by 30

His ISF is 90 so it;s the reverse of a correction he needs 90/30 of a minus correction being 3

so his blus would be 4-3 = 1

BUT it depends if there is any active insulin...(I think that's any bolus given up to 4 hours previous) that would be deducted from the 1 to give the bolus needed

Make sense???

[Hollyb]

Hi,

There is one more factor that makes this easier to figure out. Sorry this is so vague -- I forget what it's called AND where I found the calculation (probably in the book Pumping Insulin) but it's how many points 1 gram of carb will push up your blood sugar and you get it from the ratios etc. you already have.

So for Aaron, we made a rough calculation that 1 gram should raise him about 5 pts; or 15 grams about 75 points (well 4 up here in Canada).

So if he's low, we figure out how many grams he needs to get up to his target, subtract that from what he's eating, and bolus for the rest. I imagine the pump follows a similar sequence, but it would be interesting to compare!

I'll try to find that formula and post it.

[Hollyb]

Hi again,

Here's the link. There's a calculator there; you enter the insulin to carb ratio and the correction factor and it gives you the new factor. I'm sure it's quite approximate -- Aaron for example, has wildly different insulin to carb ratios in the morning and an lunchtime, so I just used an average.


http://insulin-pumpers.org/howto/HOWTO-calculate-CBS-1.shtml

[zimbie45]

HI
any any one please correct me if im wrong... this is what i would think and i compared my math with calcualtions and it seems to work..when we where on lantus and not pumping we had to do all the calcualtions our selfs

example

( bs = current blood sugars)

bs goal was 150
isf was 120

so we would take bs -150/ 120

ok so for a high of 200 it would look like this

200-150-=50 50/120 = .41 ( so we would round up to .5 and give an extra half on top of what ever we had to do for her carbs

well for a low basically we just gave her extra carbs and called it a day, but the math still works if you dont do that

example for a low

75-150= -75 -75/120= -.62 so the pump should decrease it by this amount....

what a great thinker your 9 year old.. now i know what is to come i a few years...

[Loweryclan]

Thanks for the info ladies! As it was he was low before dinner so I'll get the logs off of his pump later and see if I can figure out what it did and then I'll post it.

Amanda

[Loweryclan]

Ok, I guess sometimes we do make things much harder than what they really are.

Last night Connor was 74 prior to dinner. At 1:15 that should be 5 units, but the pump subtracted .5 for the low. The .5 was his BS(74) - Target(120) =46 / ISF (90) = -.5

I think I was trying to confuse it too much PLUS when I was first asked and trying to figure it out I didn't have all the facts the other day. There was IOB playing into the equation that I wasn't thinking about then. Now THAT is math I will gladly leave up to the pump. I do have a copy of Pumping Insulin that I think tells you how IOB is figured up, but again, that is more than I want to deal with! LOL

Amanda