You Make the Call

Your CGM shows you on a sharp downward trend. You've gone from 210 to 100 in about 30 minutes. Fortunately, you're about to eat a full meal.

Do you:

1) Eat the full meal without a bolus and see how your BS plays out before giving yourself another bolus later on to cover whatever the downward trend didn't cover.

2) Eat the full meal while giving yourself a bolus less than you'd typically give for the food based on the trend.

3) Forget the meal, and eat some fasting acting sugar first to level out your BS, and then have the full meal with the normal bolus dose you'd usually give for the food you're consuming.

4) Something else?

Well first off I would double check with my meter sometimes the CGM’s can be off for what ever reason not often for me but every once in a while. I personally would not bolus for a meal with this trend till after the meal. it is easier to correct for a high after a meal then to over dose on insulin with a low and really struggle to get it up and then you have to worry about over treating the low and becoming high so I would just take the easier route and do a wait and see. 1 high is not going to cause problems and since you have the CGM it will tell you when you start to go out of your target range and you can treat accordingly.

I’d probably to #2, but I’d keep in mind that I may need to bolus again later in case my “adjustment” took too much out of the bolus…

With Apidra these kinds of drops happen for me all the time though… but it also has very little “tail” for me when it stops working, so if the end of that 100+pt drop was close to two hours after the prior bolus I’d probably bolus for the next meal as normal, and not worry much about a low. I have countless drops like this documented on my CGM.

IF a fingerstick reading confirmed it, I’d go with #3.

2b) eat the meal giving myself 85% of the bolus in the form of a 30 min infusion instead of all right away.
-after double checking with my meter, of course.

I need to know how much was on board and at what time the original insulin was shot in to know what to do!
In another one hour, I would personally expect mine to go down about 50 % more or to 45-50, figuring I’m on the 2nd and a half hour of use. Therefore, I would pop (for myself) 6 g glucose tab and eat my meal and give myself the insulin to cover my meal.
If you know exactly what your grams raise you and what your insulin unit lowers you, you can figure it within 10 mm/dL.

I’d probably eat the regular meal, and cut maybe 15% off the bolus to cover the trend. Usually i’ll spike up a bit before my insulin kicks in, so it’s not a huge problem for me.

Bad choice base on a CGM. The CGM says “check my BG”, nothing else. Without the following information no action is appropriate:

  1. As med464rescue said, Check BG now
  2. Check BG in 15 minutes
  3. Based on the first and second BG test and what the last meal and insulin amount was, take the step that will stabilize your BG and with insulin or food.
  4. Based on the action taken, you may now make the choice.
  5. If needed, recalibrate the CGM.

Sorry to sound so uppity, but w/o considering ALL the factors that can impact BG, up or down, no decision will have the action you plan, unless you are lucky. You can easily be misled by a CGM if you do not confirm BGs with a meter before taking any action. T1D is a tough balance with a lot of variables to manage and consider 24/7.