Correction dose when BG is going up or down?

Hello fellow diabetics:

I’ve had T1D for about 47 years and now have a t:Slim X2 and Dexcom G5 (that, as a Medicare guy, I hope will be upgraded soon).

I’ve got a question about correction bolus and how you do or don’t adjust that if your CGM readings are going up or down.

For example, if my current BG is 200 mg/dl, my target is 100 mg/dl and my correction factor is 50 mg/dl/unit, my guess is that most of us would agree that if my current BG was FLAT at 200 mg/dl, then an appropriate correction dose would be 2 units.

However, if my current BG is 200 mg/dl (and by that I mean CGM reading which I know may not be the same thing) and is going up by 1 mg/dl/min or even 2 mg/dl/min, do you increase your correction dose and, if so, by how much? The same question, of course applies if my current CGM reading are at 200 mg/dl but dropping by 1 mg/dl/min or 2 mg/dl/min.

In other words, do you adjust correction dose based on both current value and rate of change of your CGM readings? Do you have a firm rule for determining that or do you a more gut-level adjustment?

Thanks for your consideration.


In the up case you laid out I would adjust my bolus up by about 1/2 unit. In the case of the BG going down, I would correct with 2U. My reason is that it takes more insulin to reverse a high than a stable blood sugar. A small drop will make almost no difference in dose.

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I like to correct for a little higher number than I actually am at. If I am going up the odds are I would be a higher number before dropping, plus it takes extra insulin at the higher the number anyway,

And the added bonus, If I look like I am going to drop too low, I get to eat more pineapple so it’s a win win! If I am out and about though I am more likely to try to dose on point. I can make any more adjustments needed later.

Once I got a CGM I realized all these ratios and correction factors I was always trying (and always failing) to perfect were mostly nonsense, and that my own intuition combined with relying on the CGM is much more effective. There are so many variables that cause blood sugar to rise and cause you to need more insulin sometimes and less insulin at other times. If I’m high I always take more insulin, I don’t pay attention to insulin on board too much honestly. If my CGM isn’t showing me go down within a time I expect I would start to drop based on my own experience, I’ll take more. If I drop too low I’ll correct with food. The actual amount of insulin? It’s different every time honestly, and the higher I am the more I need.


You just made an excellent case for avoiding the Bolus Wizard, which is what I do about 90+ percent of the time.


I agree, cgm can lead to a much different thinking about insulin dosing and timing to eat. First you see almost real time what impact the insulin and food does, and see what YOUR individual circumstances are.

Stephen Ponder’s website and book “Sugar Surfing” explains and demonstrates this well.

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This is the joys of having a CGM with trend arrows. The doctors at TCOYD talk about this a lot. A number of 120 tells you currently your blood sugar is 120 but with a CGM a 120 with two arrows up tells you some action maybe needed or 120 with two arrows down tells you some action maybe needed. Those arrows really do help me keep my sugars in my target range. Dexcom now has a leaflet in the box that give you some guidelines on how to adjust, keeping in mind that your ratios and corrections will be different. Wish I had the paper with me but I am sitting at Starbucks having my pre work coffee. Maybe someone has it and can post it.
A static number is just a number. A number with arrows is telling a story and now a story that can have a happier ending with intervention. Good luck and hope you enjoy the knowledge a CGM can give you as much as I have!


I tend to be less formulaic in these situations as I know my multi-variable gut instincts enjoy a higher percentage of success than employing a formula. If you want to see a formula that looks reasonable to me, consider the one developed by Steve Edelman and Jeremy Pettus of TCOYD, both endos and T1Ds. It’s at least a good place to start.

Here’s a presentation with similar information.

And another document

Continuous_Glucose_Monitoring_Guide_by_Dr_Steven_Edelman_and_Dr_Timothy_Bailey.pdf (1.2 MB)

Thank you all for sharing some good and useful information. It gives me a lot to look at.

I’m particularly embarrassed by the fact that there is relevant information in every box of Dexcom sensors. I’m going to blame my prior failure to read that on a Y chromosone and failure to read MOST instructions. Shame on me …

But thank you all. I now have a much better set of information as to how to determine correction boluses. And, thanks to those of you who pointed out that it takes more insulin to beat down high BG levels … I seem to chronically forget that fact.

Thanks again,


Yes, I do this. I go off of gut and by taking recent events into account.

So very true @Terry4! I also don’t use the guidelines as they are listed. Each number is a different situation but I do know if there is 2 arrows up, if I don’t do something, even with insulin on board, I could be higher than I want. I tend to be a little sensitive to corrections, so sometimes just a .3 will do the trick. Sack and everyday is another experiment in the making.

I always take the arrows with a grain of salt and pay more attention to the dotted line. The arrows are only a prediction based on the last three readings over the last 15 minutes. It doesn’t acknowledge when you’re straightening out or when the line starts to change directions.

From a pumping insulin book, if you are using cgm and have a diagonal up arrow, add 10 points to bg level then issue a correction bolus. 1 vertical arrow, add 20 points. Double vertical arrow at 30 points. You can experiment to see what works best for you. Similar for diagonal down arrow but subtract 10 points. If I have have a Vertical down arrow, I usually don’t take any insulin and eat something.