Glucose rising/falling and correction dose?

Diabetes Technology
#1

Hello insulin pumpers and CGM users:

I currently use a Dexcom G5 CGM and a Tandem t:slim X2 pump … although I think that my question is not brand specific.

In my example, assume that my target glucose level is 100 mg/dl, that I have a correction factor of 50 mg/dl/unit, and am currently reading a glucose level of 200 mg/dl.

In that case, if I have a current IOB of 0 units, and enter a glucose level of 200 mg/dl, the pump will calculate a correction bolus of 2.0 units. That seems correct (and logical) if my glucose is steady at 200 mg/dl.

However, if my glucose level is rising significantly at that time, it seems as if the calculated correction dose 2.0 units is too low. Conversely, if glucose level is falling significantly at that time, it seems as if a correction dose of 2.0 units is too much.

While I believe that more automated correction dose calculations in future systems will better compensate for rising or falling glucose levels, I’m curious as to how you calculate a correction dose if glucose levels are rising or falling.

To make this more concrete, how (if at all) would you adjust a correction dose if your glucose level was 200 mg/dl but rising at 1 mg/dl/min? Or if it was the same instantaneous level, but rising at 2 mg/dl/min?

Thank you for your consideration,

John

#2

No one here should be giving you dosing instructions nor suggesting that what they do is pertinent to your situation. You should speak with your endo if you want dosing instructions

#3

Dave44:

Yes, I always check things out with my endocrinologist and my diabetes nurse (who is also T1D …), but I was hoping to get a sense of the things that others do. There are clearly some bright and creative folks in this community that come up with creative solutions to all manner of things.

I certainly understand the guidelines quoted below, but thought that asking folks what they do does not violate those guidelines.I certainly do not plan to make any changes to my strategy without discussing this with my own endocrinologist and diabetes nurse.

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Thanks, John

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#4

I am going to ignore Dave44’s caution and share my feedback. Pump recommendations are very elementary. Just looking at a current BG reading misses so many important things.

I encourage you to look beyond the simplistic pump recommendations. Look at the bigger picture. Consider all of the factors:

  • Which direction is your BG going?
  • How quickly is your BG going up or down?
  • How active have you been recently?
  • How active will you be in the coming hours?
  • Since different times of day often require different dosing, what time is it?
  • What kind of food have you had?
  • What are you about to eat?
  • Are you having dessert?
  • How well has your body been responding to insulin today?
  • How long before you are going to eat?
  • Is there easy access to a sugar source later if you get low?
  • Are you alone or do you have a safety net if you get low?
  • Do you want to run lower or higher?
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#5

Unfortunately a pump is just a computer that works with the numbers entered into it. Current pumps don’t think about previous situations or what is currently happening. The artificial pancreas type pumps in trials do use that info, to make a more complete decision on what to dose.

But until that happens, everyday is an experiment in the making. And as stated above, everything needs to be taken into consideration. It can be mind numbing and exhausting. But keep records and see what worked well today and what didn’t and use that info for the next time. Those records will also help when taking with your medical team. You will have everything right there when stating what happened.

A pump is a great tool to help with your management of your diabetes but it sure doesn’t make it go away. It’s a 24/7 battle. I find the flexibility is the big thing and biggest reason I love my pump but it is a lot of work. Good luck and keep fighting the fight!

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#6

With us, in terms of @Eric2 first two points (although completely agree - everything needs to be taken into account), in general we will add about 1/2 unit for what I would ballpark to be a “moderate” increase BG rate per cgm. As well, I will try to guess-timate where I think the BG will be at when the insulin starts to hit. So, based on rate and ICF and BG and DIA and such, I might add another 0.75 units if I think the BG will end up being another 30 points higher by the time the insulin kicks in.

And if we over-dose by a bit then I would try to catch it on the downside maybe around 100 or 90 (depending on drop rate) with some carbs with the intent of trying to level out at 80. (Or whatever target you might be attempting at the time.)

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#7

The initial post raises a question whose answer has often been mentioned on this forum. Although we all have our standard insulin dose to reduce the blood sugar by x amount (for me it is now 1 unit of insulin reduces the blood sugar by 40 units), if the blood sugar goes very high, it seems to accumulate ‘interest,’ in what the correction dose required to bring it back to normal is much greater than what would normally be calculated. In part this may be because blood sugar measures produce only a static value and do not indicate the vector, so some of the higher readings may represent a value like ‘250 rising at 50 per hour,’ so the correction dose will have to take the unmeasured vector effect into account. But it also seems that even a stable high blood sugar level has some additional resistance to being reduced, so just empirically I think we have all developed fudge factors to adjust our standard insulin to blood sugar ratios to handle higher levels.

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#8

When I get to a little over 210, my insulin resistance increases, so I goose up my correction bolus to compensate.

It’s something to consider and discuss with your Endo, and, unfortunately no factory pump can adjust for that.

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#9

Thank you ALL for your thoughtful comments. You each made useful comments and suggestions … I appreciate the fact that you took the time to do that. @Eddue2 provided a very nice comprehensive list of many of the factors that come into play. Other comments were equally useful. To be honest, I hadn’t really considered the fact that insulin-to-carb ratios and correction factors might change at higher glucose levels … but have certainly noted that it seems to take a lot of correction dose when glucose levels are high.

Having been diagnosed with T1D in 1972 during my first year in grad school, I can certainly say that we have come a LONG ways. With the advent of excellent pumps coupled with new CGM systems, it’s an exciting time for us … particularly as we are just in the earliest phases pf integrated pump/CGM functionality.

Thank you all,

John

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#10

As much as we like to use our basic formulas to help control blood sugar, there always seems to be some “x-factors” that play a role. I like the formulas because they give me a place to start my thinking. They can get me in the right neighborhood and then I can start to add or subtract based on a number of other factors. Monitoring BGs post-fix is a great way to not only learn but also to stay safe.

Like many things in medical practice, the best medicine is a combination of art and science. @Eric2 has made a good list of things to think about and I like the variety of points made by other commenters. This is a good issue to revisit. Good questions, @John_S2!

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#11

@John_S2: To make this more concrete, how (if at all) would you adjust a correction dose if your glucose level was 200 mg/dl but rising at 1 mg/dl/min? Or if it was the same instantaneous level, but rising at 2 mg/dl/min?

Given my Dexcom, I feel free to try adjustments to the wizard’s suggestion, because I can watch closely to see whether they work well in my body, today, and if not I can fix it with glucose or insulin to get a good result.

So on your t:slim, you could enter your glucose of 200, let the wizard calculate a 2u correction, tap on the units and type a mildly higher bolus amount because you observed that your glucose is still rising, and watch what happens. Try these kinds of compensations and learn what your body needs to get a good result in these circumstances.

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