Medtronic 670g Auto Mode making me go low

I’ve been on Auto mode since April, give or take. While the system has done wonders to reduce my A1C and I’m thankful for that, it isn’t without problems…

The one that’s troubling me right now though is that between roughly 5:00 pm and 7:00 pm, my pump over-delivers. So I’ll check my blood sugar at or just before 5 PM and it’s normal. Then I drive home. By the time I get home and get settled, my blood sugar may have dropped by as much as 30 or 40 points, from a level of 100 to 140 to 60 to 70 in less than an hour. If I’m active and not just commuting (say, going to the store and walking around for 20 minutes or etc.) I’m practically guaranteed to go below 60 in that hour. If dinner is delayed past our normal 6 PM or so, I’m more likely to go low. So if I plan to have a late dinner or to do anything physical after work, I know to snack first or else.

I eat lunch between 11:30 and 12, so the meal bolus is long done by this time.

It’s nuts. This happens at least 2 or 3 times a week. So yeah. The AI is trying to kill me. ^

^ (This is hyperbole. Please note that fact.)

Has anyone else experienced a pattern of lows with the 670 Auto Mode? My diabetes specialist said there wasn’t anything she could do, so I’m kind of at a loss.

Are you SURE that the CGM data is accurate?? I don’t have that model, so not really conversant with the settings, but is one of them your insulin sensitivity factor?

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There are a few things that might be happening. First, you must talk to your Diabetes Educator or doctor before you make any changes to set up.

Second, think of lowering your carb ratio for the afternoon. Most likely it is out of wack. I suggest loosening it by about 10% per week until you have it in range or high, then make carb ratio adjustments to hit it closer to real.

Third, think about your carb counting. You have to hit it very close for it to be accurate. It is said you might error by about 10% and still be in range. But you cannot use swag and expect to be in line.

Finally, think about your insulin duration (active insulin time)

Delivery settings, Bolus estimate set up, Active insulin time. Your setting may be too short. Try increasing it slightly no more than 30 minutes in any week.

The issue may be some of all three. You have not said how long you have been using your pump, but if you early int he process, it will take time to get the settings correct.

Note: I am a Medtronic ambassador. My opinions are my own. They did not pay me to say nice things. OK, they sent me a shirt and a cup but even I am more expensive than that.


Not sure who you mean by your “diabetes specialist,” but I would call your Medtronic trainer / local rep. They are the people who will be most likely to know what are good parameters to change (for example, different insulin duration, as suggested above).

You gotta do something about that, @CaM2. Don’t delay. I had issues like that last year (I was dropping 100 points an hour) because I was way over-basal-ed. I got stuck in traffic one day (during a 2 hour commute home) and crashed my car just before I got there. It sucked sooooo bad.

Need more feedback from a 670g users.

Diabetes specialist meant my Nurse Practitioner, whom I see every 3 or 4 months.

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That’s what I assumed and this person may or may not know enough about pumps in general, let alone the 670 Auto-mode. I hope by now you have reached out to the Medtronic reps!

I’ve heard this before. Doesn’t anybody know about this on the forum? Its an interesting question that pops up. I’m gonna look through old posts…

i think these are 670g users that might be contacted…The Auto Mode experience: 670G two weeks in

@DrBB @Lorraine @njsokalski @DanP @Jane_Vaugh @Lisa77 @Dave44

@CaM2, If this starts to get worse and you dont find workable solutions, maybe you could always go back to manual injection until you do. (I realize that it might not be THAT serious, but it may be. Sometimes I find that when my sugars are super stable, I become less resilient to dealing with lows and they can become an issue for me.)

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Nothing to add to what @Rphil2 said, except maybe a few refinements.

  • Re carb ratio, I went back and forth about this multiple times, but my understanding is that it only affects meal boluses, so if the problem is the microbolusing rate, as it sounds like it is, then carb ratio won’t affect that.
  • AIT does have a big effect on microbolus rate, and is the single most powerful parameter to adjust.
  • Insulin sensitivity setting, mentioned by @Dave44 upthread, is disabled in auto. Correction microboluses are adjusted dynamically based on sensor input and your history as saved in the algorithm rather than a fixed ratio setting, so adjusting this will have no effect.

If I had to guess, I’d say it’s going to be AIT that either fixes this or leaves you without a solution. Of all the reports I’ve seen from people who gave up on auto (including me), it seems they fall into two camps: those who keep running low after extending AIT to the maximum, and those (like me) who keep running high after they’ve dialed AIT down to the minimum. I’d probably still be using auto if they allowed me to set AIT just a bit lower——or provided the ability to adjust the target at all, which is the real issue. It’s not a matter of patience; I gave it 6 months and had a huge amount of back and forth with my endo, CBE and Medtronic trainer trying to get it right. I really think the design just too rigid to accommodate the full range of physiological profiles out there. If they’d built in just a bit more flexibility they’d have a lot fewer people who gave up on it in frustration.

ETA: sensor accuracy, especially overnight, is another issue, but I think more flexible control over the settings would allow you to compensate for that.


thanks for explaining that. I have no idea why Medtronic sees fit to ignore ISF, do you?

Yeah, I haven’t had time to contact my Medtronic person yet. That’s on my to-do list. Awkwardly enough, my doctor’s office (the Endo / NP mentioned early) specifically told me NOT to contact Medtronic, to go through them. Which felt weird at the time, but I haven’t had a need so… this gives me an excuse to defy that request. (She was leaving at the end of the year, so I don’t know how the replacement will handle things.)

I have other complaints about the Auto Mode. But this is the one I can point to and say “surely THIS ONE can be fixed. Right?” (The others center around the sensors and their unreliability with my body. I see calibration fails causing sensor fails on 1st day of sensor about 30-40% of the time… I also see weeks where the sensor data on screen looks good, but the algorithm doesn’t trust it, forcing me to enter BG values every 3 hours. Those weeks SUCK so much.)

Overall, it really feels like Auto Mode is a beta-test system that’s not quite ready for production use. Like it needs to mature another generation or two before it’s really ready.

Yes or your medtronic trainer. I image the NP will refer the question to the trianer, but in order to give medical advice I had to say call your NP, doctor, trainer etc. Certainly do not start this journey alone .

Note: I am a Medtronic ambassador. My opinions are my own. They did not pay me to say nice things. OK, they sent me a shirt and a cup but even I am more expensive than that .

Just to be clear, the pump still does have a fixed ISF setting, but it only gets used in manual mode. In auto mode the algorithm is retaining data about your physiological response to the correction process in the past, so instead of a fixed ISF it’s doing the same thing only in a more nuanced way. Which in theory is a really great feature. I know for me it takes a lot more insulin to get me started down from a spike around 230 than for one nearer to target range, like 170 or lower, so a system that can respond to that difference would be much better than one that’s pinned to a single ratio. But that advantage is offset by the designed-in settings. Not only is the standard target set at 120, but it actually calculates corrections based on a target of 150. The regular target is still 120, so the point isn’t to leave you at 150, but in practice it takes a really long time to get you all the way there. For me this was a big problem in the mornings, particularly, because of DP. The sensors always seemed to undershoot overnight, and I was still working my way down from DP when pre-bolusing time for lunch came along. Felt like I was always struggling to catch up and never quite getting there.

For those who keep running low like the OP there are other factors at work and I didn’t experience that so I’m less informed about it. But one thing is that when you’re low, the only thing the pump can do is pause the microbolusing, and there are issues about that as well. It can totally zero out delivery, but there’s a four hour limit, after which it will kick you out of auto and demand a finger stick confirmation. The process of getting back into auto can be fairly laborious, and is especially annoying if it happens in the middle of the night which is exactly when this pump is supposed to shine, supposedly eliminating the worry of overnight hypos. Ends up demanding attention when you most want to rely on it to take care of business FOR you.

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Ditto that from me. It’s deceptively similar to a standard pump but the underlying logic is very different and I had a lot of assumptions going into it based on my previous pump experience that turned out to be mistaken. Also, despite my negative comments above, there are a lot of people who are very happy with it, and virtually all of them say it took months to get it really dialed in right and experienced some discouragement at first. So I wouldn’t want to dissuade anyone from putting in the effort even though my own experience was ultimately negative.

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I’m glad I’m not going to get a 670. :slight_smile:

Did anyone suggest “Drive faster”? :wink: How about an hour before heading home set the “Temp Target” for 2 or 3 hours long. That will change Auto Mode’s target up from 120 to 150 and may offer relief. Maybe you’re subconsciously anxious about driving home and the stress is lowering your blood glucose level. I don’t know… I think that can happen. Have you tried having a snack before leaving work? Good luck.

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I agree. Snacks in the car. I feel uncomfortable about using a pump at all if the sensor isn’t reliable. This makes me very uncomfortable. You are trying to fly a plane without any instrumentation.

Speaking of which…I need to put in another sensor. My blood sugars low right now.

Thanks for your comments, @DrBB. I find that I have some difficulty staying above the low limit overnight. However, despite any hitches, my results are miraculous to me: typically my time in range (70-180) averaged over 30 days is about 92% and my time below range is less than 1%. I’ve been using the 670G for almost one year. (I’ve used other MedT pumps since 1980.) I’m a happy camper!

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This is exactly why i don’t CGM with loop. I also use the blood sugar to help me determine how well the infusion is working. Often times I am in a bad spot or the cannula has moved from yoga and I need to change my set. If I was relying on a loop I would be pumped with excess insulin.

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Ever try a steel needle set? I had failures, pain from cannula sets, and you can’t move them–they must be replaced if there is an issue with coming loose or due to pain.