670G Automode - suspending question, active time question

So far I am loving my switch from Tandem back to Medtronic 670G. Now that I am running in Automode, I noticed it never Suspends on Low, and I also know that this feature turns off when you switch to AutoMode. I don’t understand how Automode handles Lows. Yesterday, was my first day on Automode (and my overnight was awesome btw!) and during the day I went in the 40s but it appeared that the pump was still supplying basal. I was surprised it didn’t Suspend. When the White Shield Safe Mode appeared, is that an indication that the pump may have suspended behind the scenes? If so, it’s confusing because the White Shield has multiple meanings and without the pump stating it’s suspended, then I just don’t feel confident when I’m low. Maybe it does suspend and I just don’t know where to look to see that. Or do I manually suspend myself if I’m going low in automode? Keep in mind I am only on day 2 and still learning so please have patience.

The second question is that I have read and some places mention that if you Active Insulin Time was 4 hours, you may need to lower to 3.5 or 3 while on AutoMode. Does this sound accurate?

Thanks everyone!

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Automode suspends before or at low. When it sees your blood sugar dropping below 120 mg/dL, which is its target, it stats cutting insulin. You can see where it is dosing and how much by looking for the pink dot on the top of your SG graph on screen. If you click the graph button and scroll over the pink dot, it will tell you the amount.
The white shield means that automode is in safe basal mode. Usually it is caused by some kind of discrepancy between the amount of insulin it has given and your current SG. If your SG is off by more than 35% from where the pump thinks it should be based on the active insulin in you, it will exit to safe basal mode. If you are at minimum or maximum basal rate for a few hours it will also go into safe mode.

I currently have my active insulin time at 2:45 with Fiasp, I was at 3:00 with Novolog and 3:15 Humalog, IIRC. 4 hours is a safe number. The doctor starts you off with a long active insulin time, usually 4 hours, so that the bolus wizard doesnt stack correction boluses. You could try lowering it to 3:30 and see how it works. Its easier to determine in manual mode once you have a closely dialed in basal rate, you can watch the graph with a correction bolus minus food to see where it stopped lowering your blood glucose.

If you had everything else perfectly set though, active insulin time would be irrelevant. Its only useful for calculating insulin on board for correction boluses.


@SpecialEDy , I realize this is an older thread but wanted to confirm what it’s saying about reducing Active time from 4 to 3. So, with Novolog, with a Medtronic 670G, 3 active insulin time would mean the Insulin works faster than at 4?

@HighHopes , Active insulin parameter is for the pump to calculate IOB (insulin on board). If you put in 4 hours then the pump tracks the insulin “usefulness” decay over 4 hours. Example using 4 hour active insulin; you bolus for a big cupcake 10 units. At hour 2 after the bolus the pump will show 5 units as IOB. If you tell the pump your blood sugar is 190, the pump won’t give you insulin if it thinks the 5 remaining units will get you ti the top of your bs range. If you put in 3 hours active, at 2 hours after bolus your pump will think you have only 3.3 units on board and will allow you to correct if it thinks the 3.3 won’t get you to the top of your bs range. A smaller number will translate to more aggressive correction bolus if you need it after a meal. Hope this helps.

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@joe, yes, this helps a great deal. Perfect explanation.

My endo suggested I make an adjustment, but I wasn’t sure why. She thought I was doing great looking at my Carelink data, but I had some issues I mentioned. I’m doing much better lately, but some days go f track and annoys me. The problems are sort of like the opposite of each other, so I’m not sure which way to go, with this in mind. In auto mode, I tend to go high for some reason, even if I have had no carbs…just water after first rising in the morning. Not every morning, but enough. Correction boluses seem to take forever and I chase the high for hours. (Is is anxiety?)

On the other hand, during the night, with no carbs, no Insulin on Board, and in auto mode, I will run low, like 70, to the point I have to treat it, UNLESS I have a 15 carb snack (no bolus) before bed. That snack seems to work ok, but I can’t forget it. It’s not about Basal rates, because I’m in auto mode. I’m wondering how switching my Active time from 4 to 3 will impact this for evening BG numbers. Hmmm….I’ll give it more thought tomorrow. Thanks.