IQ Control results in worse control - ways to improve?

I recently upgraded my Tandem T-Slim x2 firmware to the new IQ-Control release and, to be quite frank, I hate it.

They’ve managed to take the good bits from IQ-Basal and combine them with mandatory settings to make the pump “one size fits all” and my EAG has noticeably increased.

I typically maintain an A1C of 6.0-6.1 or so between sugar surfing and setting an IQ-Basal rate around 85-90 at night and 100 during the day. I keep a very close eye on my blood sugar and manually adjust settings as necessary.

With the new update I can no longer run a basal with any kind of automatic shutoff at anything less than a 110, and I have to deal with the extra inputs to cancel out the pumps “carb counting” and “insulin adjustment” requests, neither of which are accurate for me.

Tandem says I can’t revert to IQ-Basal, so has anyone found a way to circumvent this system or make it more aggressive? I have set the weight and daily insulin to their maximum allowable values and set a correction value about twice as strong as my actual value to make the algorithm a little more effective, but it’s not good enough yet and I’m considering jumping ship to an old metronic pump and a DIY closed loop. Any tips or tricks before I do?


I’m sorry to hear that Control-IQ isn’t working well for you. For me it is doing a pretty good job … but my control coming in wasn’t nearly as good as yours.

There has been a lot of discussion here as to how to get Control-IQ. I think if you search this forum for Control-IQ you get some other things to try. As I recall, some are running in sleep mode virtually around the clock. Others seems to have dialed up basal rates including some of the things that you have tried.

I would search for some of those alternatives before giving up.

Best of luck.


Are you keeping it in sleep mode all the time? I, too, hated Control-IQ until I figured that one out.
The sleep activity has a much lower target range of 110-120, and there’s no limit to how long you can keep that activity enabled. It’s still not quite what you want, though. Myself and others here, like @Hammer, increase our basal rates, also. That will actually weigh down your average Mine are increased 20-30% higher than my real needs. The variance is because I flattened out most of my previous time segment changes.

By using the higher basal rates, though, you have to trust in the G6 system to be accurate and suspend insulin frequently to prevent lows. You also need to remember to change back to your old profile during dexcom warmups, or else you’ll plummet while you have no data.

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I am a DIY Loop user and I dread the day when I have to switch to a system that no longer allows me to run at my 80 mg/dL target. My plan is to mis-calibrate the sensor. When my BG is 110 mg/dL, I will calibrate with 80 mg/dL. Then the system will try to keep my BG at what it thinks is 110 mg/dL, which really is 80 mg/dL. Not ideal. I know. I am on the lookout for better ideas.

I hesitate some to say, but I leverage every single data point that I can manipulate.
I set max weight and TDD.
I also use more basal than needed. Same trick I used with Basal-IQ.
I also changed my carb ratio and my correction factor.
One thing, I didn’t want my pump to give me too much insulin if it lost connection with the G6 for too long. So I am not TOO far overboard with the basals.
Thing is, I know what I should be giving myself for a bolus to get to 85, which is my real target.
But, with a MUCH stronger correction factor, it will be giving a lot stronger basal when needed than it would otherwise.

One thing I do is to see if I am going higher than I intended from a meal, I will do quick correction boluses. I let the pump calculate them, then figure out if I will let it do it, or make my own bolus.
I find that if I am not too high, I will use the pump’s bolus.
If I am pretty high, I usually scale it back some, but not always.

Btw, my correction is now at 1:8 and I am contemplating lower it another point soon.
This is safe as long as I pay attention to what the pump tries to give me for a bolus. Honestly, it is rarely off that much! Kind of scary.

Either way, I am happy with how I have it working for me, for now.
I know that it works far better than it ever did before. And I know that I will keep tweaking it some more to fine tune it.

@Helmut, I don’t suggest setting the G6 off your number. I think that could be more problematic than working within our limitations. And hopefully that by the time you are forced to may that change, that the current system will be better by that time.

Tandem says they plan on a yearly update.
We can all guess that they had to play it safe with a new system being fully released. And that they have more programming tricks up their sleeves.
I also image that they are now in possession of a massive amount of data to truly improve their algorithms.


I’m just gonna say this, come what may.
Its possible that this problem is not specific to your APS system, but to all APS closed loop systems. Always has been a problem. Always will be.

-Ex Looper who had the same complaint and was considering switching to T:Slim

I was also 6.1. Jumped to 6.4 on APS

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Yeah, being able to understand and manipulate the system is going to be a requirement for any product out there.
It is just impossible to tailor build something for everyone.

Still, that being said, my A1c with Basal-IQ was 5.2, and two months on Control-IQ, and eating a LOT more carbs, I dropped to 5.1 on my A1c. So it obviously can work, for me, with my changes.


Those numbers are great. Can you expand on how you use it a little more?

My normal basal rate it 0.4 - 0.6/hr with a 1:50 correction factor and about a 1:13g carb factor. I’m about 210 lbs and use 30-40 units a day.

I tried what was suggested here and ramped it up over a few iterations and ended up trying a 1.5/hr rate with a 1:25 correction factor with IQ-Control set to 300 lbs and using 100 units per day and sure enough, it dropped me into repeated lows so there’s some potential there. I just need to dial it back until it’s reliable.

Are you using a high basal and IQ-Control in place of a loop and skipping some small carb load volumes entirely or just ramping up your basal until it keeps you where you want to be and blousing as normal?

I have a higher basal, but not dangerous.
I have the max TDD and weight.
I changed my correction and carb ratios to be more aggressive.
It is a balance of all things.
I also have to attribute a lot of this to using Fiasp with the Control-IQ. I feel that they work very well together.

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My A1c was 7.8 on Basal IQ and I was on Basal IQ for a bit over a year before starting Control IQ in Jan 2020. My latest A1c was 6.2!! The lowest it has been since before I was diagnosed in 1983 and on a pump since 1985. I expect it to continue to come down as that datapoint included a full month of Basal IQ glucose data.

I followed @Hammer suggestions of using higher weight and TDD and enabling Sleep mode all but one minute of the day…1159P-1200A.

I worked intensely on my Basals, ISF and Insulin:Carb ratios with Basal IQ…this is key to having this system make good decisions for you. Having these parameters dialed in gives a good solid foundation for Control IQ to work. I would suggest that @JR1 fine tune these parameters without Control IQ and then move directly to Control IQ Sleep mode with a 10-20% bump in body weight and TDD…too aggressive on these and you lose the benefit of sleep mode when you are actually sleeping. A year ago and the previous 36 years with T1D, I would have never gone to bed with a BG of 80…now I do this routinely and seldom have have a snack in the middle of the night. I am also much more tolerant of low BG…I often do not treat low BG unless I have had no meal within the last 6 hours or unless I have some strenuous exercise or activity.

While Control IQ has been more than promised for me, an additional parameter that came to me from a Forum member(I can’t find the post now to attribute to them…sorry) is the number of carbs consumed. I have in the last three months or so, started to limit my carbs per meal to less than 20 if possible. This has also naturally lead to intermittent fasting as a result. I will have 15-20g carbs at breakfast with 4-5oz of lean protein and some bacon. I cover this with a 35:65 extended bolus for 1.5hours. I am not hungry and often flatline my BG for 10+ hours. I do not eat lunch and will eat another low carb snack mid afternoon so I can have a normal dinner time. This has made a world of difference in my BG control and Control IQ works very well in this scenario.


I am able to trick my tandem to give me lower target set point.
I decreased my sensitivity by moving my ratio to 1:20

And also use sleep mode all the time.
My average glucose when I’m not eating is right around 90 and during sleep it’s slightly higher around 93.

It took me a few months to figure out how all the settings effect things.
My last a1c was 6.1. I’m happy with it.


How did mis-calibrating the sensor work for you?

I’m thinking of calibrating my t-slim 10 mg/dl higher than the actual BG finger stick reading.

I’m hoping that Control IQ will cut off when my real BS is 100 mg/dl, rather than cutting off when it reaches its 110 mg/dl minimum.

Does anyone see a problem with doing this?

I’m very low carb (30g/day) and my average BS is 97.

I personally think that it is a bad idea to mis-calibrate Dexcom although in theory it sounds like a workable solution. After the first day, I find Dexcom to be mostly reliable and I hate to think of messing it up by constantly telling it that it is wrong.

The unfortunate fact is that Control IQ is much better at preventing lows than preventing highs. I get frustrated because I get long insulin suspensions that result in highs later on. I never understand how people say that they can get an average of 90 when Sleep Mode targets 112-120.

My current regimen is to use Control IQ at night and turn it off during the day.


If you decrease the sensitivity setting for night times it will allow you to run lower.
When I’m in sleep mode, I run about 98 at night.

Could you explain how to decrease the sensitivity setting?

Here is definition from Tandem.

Correction Factor (Insulin Sensitivity Factor)

“The amount of blood glucose (mg/dL) that is lowered by one unit of insulin.”

You enter it in your Personal Profile settings, and it can vary for each time segment, as Correction Factor. For example 1:40 means 1 unit will lower bg by 40 (if flat), and influences how Control-IQ adjusts insulin.

If you use T:Connect app or check status screen on pump, you can see current value.

I now also consider to only lower insulin sensitivity. With DIY Loop and target 80 mg/dL I cannot do that because I overshoot on the low side. This should no longer be an issue with target 110 mg/dL.

In direct regards to Control-IQ, correction factor determines how aggressive basal adjustments are, and how much it delivers as an automatic correction bolus. The lower the number, the more insulin it gives or withholds as appropriate. The greater the number, the less Control-IQ can affect you and the longer it takes to bring you back to target.

Control-IQ will reduce your basal anytime you’re below 112, but if you raise the CF setting a little bit, it will take a looonnnng time to get back to 112. If you go ahead and increase your basal just a touch, too, it will sorts cancel the effect of the reduced basal out. If you get the basal/CF balanced right, you can hold steady below the forced target.

You really have to be careful about making small adjustments, though, because increasing the correction factor makes the system less capable of preventing lows. It’s not a setup I’d recommend during the day, unless you’re exceptional with your bolus habits.

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Does it change based on prediction of 112, or actually hitting it ?

It’s all based on predictions, but admittedly I often forget that when I speak.

Of course that’s just default mode. Not sure where my favorite graphic is at the moment.