670g Meal Woes


#1

Hey everyone - I have been on the 670g for a while now, 99% of the time in auto mode. I am also on a mostly low carb diet…I typically eat less than 60 carbs per day on a normal day. This diet in tandem with auto mode has been great. However, I notice that if I eat any sort of higher carb meal at any point…really anything about like 30 carbs, I always go high, even if I bolus well before the meal. Is anyone else experiencing this? My best educated guess is that 1) I may have been doing this before and just not noticed because I was not on a CMG 2) Because I am not already getting a steady basal delivery, I do not have enough insulin in my body to cover the food when it hits before my bolus actually hits.

My other issue is that once my blood sugar is high, the auto mode correction system seems to fail pretty miserably. The ratio of insulin I would normally take for a correction is significantly higher than that of the auto.

Would love to hear if anyone else has experienced this and resolved it.


#2

I have breakfast spikes even in Auto Mode, but it comes down (once I figured out the appropriate carb ratios).

This will usually be the case, because of the Max Delivery restriction. Auto Mode determines a maximum amount that it is allowed to use in the microboluses, so when you are high Auto Mode will most likely be unable to bring you back down without you doing a correction bolus. The purpose of Auto Mode is more to keep you level and prevent you from going high when not eating, but when food is involved, it is your responsibility to enter (at least approximately) the carbs so that the pump can give you enough insulin. I know, this is frustrating, it’s one of those safety features that many of us wish wasn’t there, but once you get all your settings tweaked (specifically the carb ratios), it should be good.


#3

Here is the actual issue with pre-bolusing on 670G: it stops giving you micro-boluses after you’ve pre-bolused, because your blood glucose is trending down. So essentially it does not calculate the meal dose correctly. Because the meal needs algorithm counts on the micro-bolus to keep doing its thing. (Let’s say the micro-boluses are correcting a high from dawn phenomenon and BGL is 175, so you give insulin through bonus wizard for meal, then wait 20 minutes. Auto mode kicked off, but needed to stay on to correct the 175.)

That’s what happens to me. If I pre-bolus while above 100, the levels will be screwed up anyway.


#4

Try changing the AIT (active insulin time). I believe it defaults to 4hrs.
I had the same problem, though I’m not low carb by any means. Changing the AIT to 2.5 helped with the after meal spikes a great deal. That along with about a 5-10min prebolus keeps me at or under 190 post meal spikes.


#5

Hi dlipscomb, I have had similar challenges on the 670G auto-mode. I know that the correction bolus calculation in auto-mode brings BG down to 150, whereas at other times the supposed goal is 120. Medtronic set it up this way for safety (one of the hurdles of getting it approved by the FDA). I, too, eat ~60-70 grams of CH a day, and have settled into a fairly successful routine during the day. I have my high alert set to 180. When I get that alert, I check my BG, enter that number into the bolus feature, and let it bolus whatever it thinks it should. (Don’t calibrate unless it’s time to calibrate.) If there is active insulin it will generally be even more conservative with the correction. Like others, I now have my AIT set at 2 hours. Sometimes I wait until my pump shows no more active insulin, then do the corrrection bolus. That usually works to lower my BG to 150, then back to 120 within a couple of hours. I am still struggling with dawn phenomenon in auto-mode. If anyone has suggestions, tips, or tricks on this topic, please share!


#6

Thanks so much! Extremely helpful tips. I made some of these adjustments when I posted the thread initially and it has already improved my experience.