Insulin sensitivity factor - how does it work when BG is below target on pump

My understanding is, if I increase the ISG, it will make my bolus dose weaker. So an ISG of 3.5 will deliver less insulin as opposed to an ISG of 3.0.

But how come when my current BG is below the target, a higher ISG will result in a stronger bolus dosage? I’m a bit confused.

I played with my pump wizard to test out what the bolus amount was in this scenario, I entered my current BG as 3mmol. Target is 6mmol.
So when ISG was 3.5 (more sensitive), the bolus I had to give for 10g of food was 1.0unit. But when I set the ISG to 3 (less sensitive) , for the same 10g, the bolus was 0.75Unit.

Can someone please explain to me why, shouldn’t the bolus amount be more for ISG 3 because it’s less sensitive?

When my BG is above target, the opposite happens whic is what I’m expecting.

Is anyone able to confirm for me please that this is the same behaviour on their pump when their BG is below target? I don’t know whether this is just my pump playing up.

I’ve googled this but unable to find anything that supports the pattern I am seeing.

In general I find that insulin is more sensitive when my BG is low, the fact the wizard seems to be giving a higher dose when the BG is low and not the other way around worries me a little - wouldn’t it be a higher chance of going into hypo state?

Okay, I’m going to go by the title of the thread and assume when you say ISG you mean ISF Insulin Sensitivity Factor.

I’m not completely sure what you are saying so to make sure I will explain what I think???

If you have it set at 3mmol (54) that 1 unit corrects
If you have it set at 3.5mmol (63) that 1 unit corrects

So starting at 3 mmol aiming at 6mmol the first correction 3 mmol requires 1 unit
The second 3.5 mmol requires less than 1 unit to correct

So the only way I can figure you would get more insulin at the 3.5 setting would be if it had already corrected a low BG reading?

So say for me I entered a bolus with a lower number than I wanted to, it gave me the bolus amount and then allowed for the correction. But I changed my settings and entered the amount in again to see what it would say, but since it had already done the correction it won’t do the correction in the figure the second time.

Could this be what happened???

:woman_facepalming:t2: Yes ISF. Sorry. Thanks for explaining. And I realised I have it all muddled up in my head.

The higher ISF will require more bolus than the lower ISF because it’s less sensitive. It holds true for both above target and below target.

For some reason I processed it the other way around for below target BG reading. It’s all good now, thank you.

Insulin Sensitivities

Insulin Sensitivity Factor (ISF) is the same term as Correction Factor used in some clinics and endocrinology offices. ISF represents the drop in blood glucose levels expected from one unit of insulin. Loop works best if you have tested and optimized your ISF settings for accuracy. Insulin sensitivities can change for many reasons including waiting too long to change your infusion set.

Incorrectly set ISF is the most common cause of roller coaster BGs for new Loop users. You will need to raise (increase) your ISF value/number to help smooth a roller coaster BG trend. You can read about that topic more over in LoopTips here.

ISF Testing:

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I find it easier to think of the 2 this way.

Carb ratio is a calculation to determine how much insulin you will need not the meal you are about to eat. If you enter your carbs and it suggests the right amount of insulin then you have a good ratio set up.

The sensitivity factor is what your pump uses to do it’s own bolus corrections and how it determines your basal rate from min to min.

So really your carb ratio does very little. You can alter that before you deliver anyway.

So if I’m eating and it says will deliver 2 units. I might say no way I need 3 and you can change it to 3. But then you should look into altering it. Just for ease of use.

Sensitivity factor is where it is at for control iq. But you need to make small adjustments so you don’t start going too low.

Best time to look is at night in sleep mode. Fewer variables.

Correction factor is the same thing in tandem.