Basal IQ frequently kicking in

My Basal IQ has been kicking in a lot, is this a sign I need to reduce my basal. I’ve attached my CGM data for overnight BG. Referring to the interval between 4am and 9am, its hovering around 4.8mmol (86.4mg) which I think is good. And its a relatively flat line. But you see that Basal IQ kicks for a very short duration but frequently. The duration it kicks in for is literally one data point, I’m not sure it will make a difference if it didn’t kick in to be honest. At this time, its fluctuating up and down between 4.6mmol (82mg) to 4.8 mmol (86mg) which is nothing.

I should also add, the previous night it was hovering around 6mmol (108mg) and again a relatively flat line and basal IQ didn’t kick in at all.

Looks like a nice flat line. If it’s not broken, don’t mess with it.

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I have C-IQ, never used B-IQ.
But my understanding is the basal adjustment is triggered by it’s prediction, so a trend up/down would initiate basal change.

Your charts look great!

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While I don’t have any inside knowledge as to the actual algorithm used to prevent lows with B-IQ, I think that I know enough about control systems to try to explain what I suspect is going on.

While my analogy is not perfect, let me use the example of you following a truck going down a long hill. I use a truck because it takes a long time to slow or stop just as falling blood sugar takes a long time to react to reductions in basal insulin.

On a steep downhill what do you see when you are following a truck? The brake lights come on quickly and stay on. You can tell that the driver is applying moderate to heavy braking force because, after a while, you can smell his brakes. This is the equivalent to rapidly falling glucose levels: B-IQ significantly reduces or even stops basal insulin for an extended period of time as soon as it determines that your blood sugar is falling rapidly. It keeps that basal insulin significantly slowed or stopped until it begins to see that your dropping glucose levels have begun to flatten out … which could be a period of an hour or more.

What happens when the same truck is going down a shallower hill … one where the truck speed is barely increasing. What do you see this time? You are likely see the driver coast for a bit, then apply the brakes briefly and lightly, coast a bit more, reapply the brakes briefly, etc.

I think that what you are observing is that the driver in charge of Basal-IQ is “tapping the brakes” periodically to keep your very gradually dropping, nearly flat blood sugar from “picking up speed” and dropping too fast.

To me, this behavior seems perfectly reasonable.

Stay safe!


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@John_S2 gave a great analogy. Except with Basal-IQ, the truck can’t slow down, it can only do hard stops, though sometimes only briefly. So you’ve got to follow that “truck” a lot more carefully, because it’s going to come to a complete stand still on the highway. His analogy better lines up with the Control-IQ algorithm, which can indeed slow down and tap the brakes.

Basal-IQ completely shuts off any basal when Dexcom predicts you’ll be less than 3.9 mmol in the next 30 minutes. This is a great thing, but also a bit of a weaknesses in the system if your BG is falling rapidly, just generally erratic (dehydrated, dying sensor, etc…), or you’re trying to intentionally lower BG pre-meal. It also resumes insulin the moment your BG changes direction, which may be too soon if you’re very low.

Basal-IQ was an incredible first generation product for preventing lows, but Control-IQ far surpasses it. Hopefully it gets cleared in Australia soon! Tandem has stated it should be available world-wide in early 2021. I’ve been nearly a year removed from Basal-IQ, so I’ve forgotten those weak points.

There are two different schools of thought on pump automation. Those who think it’s a tool to be used to maximum benefit and love to see it working, and those who think it’s a tool to be used to make settings adjustments and try to avoid pump intervention. I’m definitely in the former category. To me, that graph looks beautiful and like Control-IQ was behaving perfectly to avoid lows throughout the night, while still maintaining a flat graph near the lower range limit.

However, I’ve gotten the impression that you might be in the latter category and looking to avoid Basal-IQ having to kick in. That’s perfectly alright, too. If you want to avoid Basal-IQ kicking in, you need to reduce your basal, though probably only SLIGHTLY. The trade-off is that you’ll run a little higher at night, but you’ve got some range to spare.

I know you’ve gotten plenty of advice about adjusting correction factor (maybe even from me!), but we’ve all forgotten that correction factor doesn’t play a role at all with Basal-IQ… while being CRITICAL to Control-IQ. It’s completely irrelevant to you right now. The only adjustments you can make are basal rate and drinking lots of water to help your Dexcom data out.

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As usual, @Robyn_H is exactly correct about the differences between C-IQ and B-IQ and their ability to “dial back” vs completely stop basal for a short time, respectively. Even with Basal-IQ, if basal is completely off for 5 minutes and then back on for the next 15, given the 20-30 minute “activation” time of Humalog or Novolog, to your body that probably looks very similar to “dialing back” basal to approximately 75% … even though it was achieved with completely digital on/off pulses of basal.

And @Robyn_H is absolutely correct: B-IQ was a great first step and C-IQ is so much better. I can hardly wait to see “Daughter of C-IQ” or whatever the next version will be called.

Stay safe!



Thanks for explaining that. I’ll probably watch it a few more times and see whether it’s consistently kicking in- at the moment it’s not, when my BG is along the borderline of my low range, it will kick in but when my BG is slightly away from the borderline low, it doesn’t kick in.

Apparently it’s been cleared which is exciting news! I think they are in the process of rolling it out training to the DEs so hopefully early next year it will be available.

Ah yes, I’m not really sure what to expect. This CGMS experience has made me think a bit differently about my control and the possibilities of what I can do with it and I’m not too sure which of the two camp i want to be in yet.

You are right, at the moment I’m in the latter one. In my head, I want to establish a “normal” baseline first rather than relying on the brains in the pump to steer me in the right direction. The more accurate I can get it means the brains will have less to do but thinking about this it doesn’t really matter because the technology is there and I’m never going to get my BG spot on because I know too well it’s going to change over time so why not just rely on the technology :sweat_smile:.

I think my bad experience with Medtronic cgms has made me a bit wary about relying on pump technologies. I am not yet confident it can be accurate and reliable. Dexcom is changing my thinking and I think I just need a bit more convincing.


Yes, it was approved and listed on the Prosthesis list at the beginning of this month. IMO it’s disgraceful that we are still having to make hopeful guesses about when it will be available rather than getting some formal communication from AMSL, and that furthermore we have to wait for DEs to be trained beforehand. I don’t know about others, but our DE had nothing whatsoever to do with the Basal-IQ upgrade, the user training is all online and all the DE does is get the endo to sign a form. In what world is a DE going to know half as much about the intricacies of any given pump as someone who has been using it 24/7 for years?


@Dylan_Sutton and @tedos:

I certainly hope that you are allowed to upgrade to Basal-IQ soon. It DOES seem silly that they are waiting for DEs to get trained … certainly in the US all of the B-IQ training (and C-IQ training for that matter) was online as well. Of course, residing in the US, I would absolutely NEVER comment of another country’s silly medical rules … stones and glass houses!

Of course, if all it takes for the DE to be trained is for THEM to complete online training, then I would likely be on the phone to the DE every day asking: “Have you completed the Basal-IQ training yet?”

I hope that your next post starts with “Hooray, I’ve upgraded to Basal-IQ …”



I think in Australia they are forcing you to get this done via the DE for every upgrade. I couldn’t get the basal iq update unless I got my DE to sign the form. So you have to make an appointment and pay for the consult in order to get it. This is a pain for every upgrade in my opinion. DEs can be useful but only to a certain point. For a beginner pumper, they are probably the way to go, but for us old timers who have been pumping for a while, I think it’s totally adequate to get it done without going through a DE or endo. You are right, we would know more about it than someone who only learnt it via documentation and not experienced it first hand.

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Hi John

We only got basal iq recently, they started rolling it out I think in June. I myself have upgraded and have been using it. Dylan was referring to control iq which was just approved but no formal communication of this has been announced yet. So we are all guessing when it will be available.

Depending on your relationship with your DE, you may not need an appointment or a consult. When we did the Basal-IQ update early last month we just had a phone conversation and the paediatrician was happy to sign the form and return to AMSL. This is through the paeds clinic at our local public hospital.

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Correct, it’s Control-IQ we’re waiting for. The issue isn’t that individual DEs haven’t been trained, it’s that Control-IQ isn’t available to anyone at the moment despite being approved.

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I wonder if the wait is on Tandem’s end? When Basal-IQ got the FDA approval here, the software was made available immediately through Tandem’s patient portal. We just had to log in and submit a request, and as soon as Tandem got the prescription back from the doctor we could download the software update.

Control-IQ was very different, though. After the FDA approval, we waited weeks for them to actually make the software available to anyone. And even at that, it was a very slow rollout. They were trying to get people to wait until they got an email invitation to start the prescription request and online training process. Those of us who read online knew it was available and jumped the gun, though. I have no idea why it took so much more time to implement than Basal-IQ, but you might still be in that intermediary phase.

Maybe logon to the patient portal and see what’s available for you, there? I’m post a link to the portal I know, but I don’t know if australian users have a different website.

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@tedos and @Dylan_Sutton:

Oops! Sorry, I lost track of which upgrade you were waiting for … and hope that Control-IQ is on your pump soon, if you so desire.

You should be pleased to learn that my confusion is a side effect of my age rather than being a complication of T1D …

I’d say “Stay safe!” but you in Australia have done a splendid job of controlling COVID-19, even during the recent surge in Melbourne over the past couple of months. Well done!!!