670g problems: why microbolus when low BG going down?

I’m new to pumps period and started with the 670g, not sure it was the greatest idea. In manual mode I’ve done very well, the trainer that’s working with me said it was the best she’s ever seen. That being said the switch to auto mode has been awful. The biggest thing is the micro bolus do not bring me back into range at all. The bigger thing that happened this morning was my sg was 52 and it gave me a micro bolus, really my bg was 102. The issue of the gap in readings aside if my sg was 52 that’s what the pump thought my glucose level was. Why did it deliver insulin? Medtronics was zero help on this they referred my to my trainer and doc. They aren’t going to be able to say why your pump did something that it in no way should have. Had anyone else seen this?


Welcome to FUD, @Dragonspirt35!

@Nickyghaleb and friends, what do you think?

I am sorry you aren’t able to understand how your pump is behaving. That is in large part why we have stayed away from any of the black box type algorithms, i.e. my son and I are too much of control freaks. I hope you get a satisfactory answer, but I suspect it will be less satisfying than it should.


Thank you. I’m a control freak too. My trainer was astonished that i asked how to record the carbs I ate to counter a low so I could do my best to not have a spike afterward.


This is exactly our fear and why we don’t do the loop right now.

That’s a great practice! My son and I constantly use data to figure out best practices, in this and other areas.

Btw, we use MyNetDiary for logging, but, by now, I feelt there are better options.

These are copies of text from medtronics

the micro bolus delivery is based on the algorithm which takes into account the direction of the glucose as well as his history. I have seen this kind of thing before and my understanding is that it delivers when the glucose is rising and that it anticipates the need for that insulin. it also takes into consideration that it’ll be anywhere from 15 to 30 minutes before that insulin has a glycemic impact. So the answer is that the algorithm delivers insulin when it is safe to do so and trusting the auto algorithm is the best plan.

My response

Ok I’m going to call bs on that
I will just type out the run down.
5:36 63
5:41 61
5:46 61
5:51 62
5:56 63
6:01 62
6:06 60
6:11 56
6:16 54
6:21 52
6:21 bolus of .05

It was in a downward track


Hi @Dragonspirt35! Yes, I’ve seen all of what you’ve described. I’m not sure how much help I can be, unfortunately, as I never found any good solutions and have since moved over to the T:slim. I’m going to go ahead though and speak openly about what you’ve asked, and you can take what’s useful.

So I think this is great news. This is true pumping. If you are figuring out how to get this to work, it means you’re really getting some nice settings and are learning how to work your basals and boluses. That’s a huge victory. Honestly, from what I have seen, many people end up back in Manual Mode after a few trials of Auto Mode, so there’s no wasted effort in getting that mode to work. If Auto works for you, that’s great, but you’re learning how to work Manual in the meantime.

I was never able to get Auto Mode to work well for me either. There are workarounds that people report working, but I’m not interested in all the trickery they describe using in order to get my pump just to give me enough insulin. Again, if you can get it to work in Manual Mode, then it’s evidence you are not broken. One would hope Auto Mode, after a reasonable amount of time, would be able to figure you out enough to keep you in a relatively good range. There are people out there who get there with their 670G. I wasn’t one, so I really can’t do much more here than to confirm that you’re not alone with these results and frustrations.

Specifically, about the Micro Boluses not bringing you back down into range, that was another big complaint of mine. It would take hours and hours to get me back to a normal number again, and that would be after being very patient and not eating anything at all. I was willing to do it in the beginning, but then I started to see what was happening, and, again, lost interest in the entire thing. I believe this slow return from a high blood sugar is called the 200 minute high excursion, and it is how they designed it. It’s very conservative. There are people who don’t mind it; some are coming from a very high a1c to begin with, or there are those who are have a different standard of what they consider too high at all. As long as I was still seeing improvement in my a1c, I was willing to sit through those high excursions and wait them out. At some point, I realized I had better control back in Manual Mode.

This morning’s case appears to be a rising blood sugar possibly from a low insulin delivery over night. I might be projecting here, but when I see anything like that that has occurred in the morning, this is my first guess. I saw it often. Your BG was a 102 because it was rising, and your SG was just lagging. However, you pump was resuming that insulin because of your trend. Most of the time it’s doing that, it’s actually a good thing. I’ve talked to people though who have received a lot of insulin at truly low blood sugars, and that usually occurs when people start using that trickery I mentioned up there. They trick their pumps into giving them more insulin and then cannot control when their pumps give them more insulin. The only reason I tell you all of this is because it’s hard to know what exactly was happening in your case, and I would hate to make it sound like it were normal if it weren’t. It looks familiar to me, and I think it’s pretty standard stuff. Just out of curiosity, did you end up with a high blood sugar??

The new transmitter… I also feel like I should mention this. How long ago did you receive your transmitter? Have you just received everything, or are you a couple of months into it? If your transmitter is not version 2.2, you might want to contact your trainer and see about getting it. Even people who have just received pumps at the beginning of the year were still receiving old transmitters, so it’s worth taking a look. I’m trying out the new transmitter now, and it genuinely, possibly appears to maybe be cutting that lag. If you’re still actively trying auto mode, you’d definitely want to do it on the new transmitter.

Don’t get me started.

I have a Facebook group that has really worked through a lot of these issues if you’re interested in hearing how others are doing. People speak very openly about their experience and are at ease in discussing frustrations and problems. The group was a 670G group right up until I bailed, and now it’s a general technology group. There might be some great ideas in there for you though… or not. :smiley: The Honest Exchange (for navigators of diabetes tools and technology) No pressure whatsoever. (Hope that’s okay, @Michel).

Dragonspirt35, please don’t hesitate to let me know if there’s anything I can help you with. I’m around. :slight_smile:


I do have a 2.2 version transmitter. I didn’t give it a chance the 25 min prior to that bolus was a downward trend and when I saw that I immediately did a finger stick. I refuse to do the trickery because I’ve heard the stories of the aftermath. My first week on the pump I was in target range 75% of the time. I think i left out I had a bad sensor too. I changed that out at 2am this morning.



So then you’re already doing the only thing I could do in Auto… and that was to test all day to try to catch it before disaster. It was getting blindsided that was the worst— not realizing there was trouble until you were already in trouble. Once I learned to look out for it, I tried to be preemptive, but at some point it was just like doing all of the prep work for dinner only to let someone else do the cooking. I got fed up doing that amount of work only to take the chance auto would drop the ball. And it did often.

I think it’s too risky. On the T:Slim with Basal-IQ, I don’t hesitate to do a manual injection… or whatever I may see fit. It’s not deciding my insulin though. I’ll drop manual injections though if I decide to try out Control-IQ. Just seems like an inherently bad idea to lie to my insulin pump about the fact I’m doing insulin on the side… when my pump is trying to decide how much insulin I need.

I’m not sure if you’re saying that was good or not. I tried out Auto Mode one last time at the end of last year just to see if I could get it to do anything differently, and I was surprised with what a strong start there was. It’s got great potential. It really can deliver a lot of insulin, but I think it weakens over time and ultimately gets locked into a a weak delivery. That’s when people start buying themselves extra insulin, and that’s when I think it sets them up for trouble… but we’ve already discussed that. I’m repeating myself. Oh, exercise seemed to really throw off my delivery, too. I’m not sure if you partake, but I watched my micro boluses tank after a week of exercise. I think, without the ability to tell the pump why I don’t need insulin during that time, the only thing it learns is that I don’t need insulin during that time. So then it hits the breaks even when I’m sitting around not doing anything.

Hope you got it replaced. If you don’t know already, they’ll allow up to 5 to be replaced online. It saves you the phone call.


Unfortunately for us, my son is really carb sensitive, so even when he is 50, he will take 6 carbs and dose insulin to prevent the crazy rise from hitting him later.