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Insulin sensitivity factor

S

spideog

Well-Known Member
Messages
164
The ISF on my pump was initially setup at 1:3 when I first started on the pump. But last week the nurse wasn't happy with the speed at which the correction boluses were taking effect so did a recalculation of the ISF for me. I'm now finding that the correction boluses are sending me low so am just going to split the difference between the 1:3 I was on before, the 1:2 that she changed me to and set it up as 1:2.5 and see how that goes.

They seemed to use an incredibly crude method of figuring it out though, just dividing the average total daily dose of insulin into 100. That doesn't sound a particularly good way of figuring out how sensitive you are to insulin when it is not taking into account other factors, such as how much your eating or exercising.

All I can find online about how to figure out the sensitivity is just similar calculations, although using the US units mostly. Can anyone explain the thinking behind such a basic method of figuring it out? Am I missing something obvious in how they come up with the numbers?
 
I have just started on the "My life" OmniPod pump - the ISF was worked out the same way - I have found that by increasing the amount I told the nurse of my Lantus gave me a more reliable ratio. How you finding it since you have split the difference ?
 
It does sound crude that calculation doesn't it, not very personal at all.

I think like most things as everyone is so different it's used as a starting based then on experience you can tweak from there..

a correction dose of 3:1 works perfect for me, i've never had to tweak it really!

Your nurse and professionals can only give you the theory and technique, only you can judge if it works in practice or not so trust yourself and your results to find your own needs!
 
Does your pump allow different ISFs at different times of the day? That may or may not be factor in your control.

You might check out Pumping Insulin by John Walsh and Ruth Roberts -- probably in mg/dl but just divide by 18 to get mmol/L

Like Ebony says, as you gain confidence you'll rely more on yourself and less on your "team"
 


Hi

Working out ISF is confusing isn't it?

I might be wrong here Spideog but I don't think your dsn has worked out your ISF correctly. She thinks that by altering your ISF to 1:2mmol will only make your bg levels drop by 2mmol for every 1u you use to correct but what happens is that the pump will use that calculation to bring your bg level back to being in target range so in actual fact the pump will use more insulin in its calculation instead of less. If you found yourself going hypo with the ISF of 1:3mmol then by altering it to 1:2mmol will only make you go even more hypo. I would try the ISF of 1:3.5mmol and then tinker about with the calculation by seeing what your bg levels 2-3hrs after you've done a correction.

You can alter the ISF to whatever you want it to be on every Time Block. At certain times of the day, your bg level may drop a lot more than it might do at other times so it does pay to play about with the settings just to see what happens.
 


By speed does your dsn think that your bg levels are lowering too quick or does she think that it's taking too long for a correction to lower you?

I apologise if I've got the wrong end of the stick
 
I wasn't going hypo with the 1:3 ratio, it was that it wasn't coming down quick enough or far enough. I was in agreement with her about that probably not being quite right, but when she came up with the number of changing it to 1:2 the percentage change surprised me. I did query it with her, but possibly asked the question in the wrong way.

I wasn't completely convinced that the ratio of 1:2 was "safe" for me so have manually picked slightly different boluses on some occasions in the last week where I wasn't prepared to risk things going too low at that point in that day. But have done several days of just blindly trusting the numbers now, with handy supply of Lucozade close by, and based on that testing am confident that it is the wrong ratio for me.

I have now set the pump with 1:2.5 and will test that out for a bit now and I'm perfectly happy with the "suck it and see" method of figuring the different settings out. The confidence that the nurse had in her calculations was what surprised me though considering how basic a way of coming up with the number was. I had also been expecting to see more vague calculations suggested on the interwebnet about it, but every page I found was pretty specific in their sums. I was expecting it to be shown as divide "this number" by "that number" and then adjust for other personal factors such as food intake exercise etc.

Guess I'm just trying to over analyse it a bit.
 
It was that it wasn't coming down quick enough.
 
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