HbA1c up after transitioning from MDI to C-IQ

I am a long term type 2 who began MDI a year ago January. My HbA1c was very well controlled in the mid 5%. In January 2022 I began using a T:Slim pump with C-IQ. The carb ratio and correction factor and basal rate were set to mimic MDI.

I have a smoother curve, but HbA1c has risen about .5%. When I was using MDI I was injection Lantus 3 times per day which did away with DP and FOTF, plus it got ride of the BG bump 4 hours after lunch.

During sleep mode my BG C-IQ runs high 90s to as high as 130. With MDI my night time BG was averaging in the 80 to 90 range.

I have done some tinkering, increased basal rate by .1 u, my weight doing small correction doses and for lunch and dinner doing extended bolus. I bolus an increase of 1/3 and do an extended bolus of 60%/40%.

This is working fairly well, but I don’t find C-IQ gives the numbers I like.

One more thing my diet and exercise are basically unchanged.

Any advice from those more experienced would be helpful.

Since your a1c was already low, you aren’t going to get that wow moment on the pump.

When I was on mdi I was running in the high 6s. So dropping to me mid 5s is awesome.

However I also changed my diet at the same time so it’s hard to tell.

The tandem pump is kind of designed to get you to a 6% on average. Which is actually higher than you were before.

The ways I have lowered mine are telling my pump I weigh more than I do by 20 lbs. and I increase my basal rates by a small amount.

Then I switched to putting my pump settings exactly how they should be and I take once daily lantus of 10 units.

This takes the pressure off my sites, which I think are being overwhelmed and used to crap out after 2 days.

So now I can leave a site in for 3 days. And I haven’t had a new a1c yet, but I suspect it will be a little lower.

My night time average is now 95. And I don’t have those stubborn highs and stubborn lows. Corrections work faster now.

My doctor wasn’t really enthusiastic about my experiment but when I go back I’m hoping she will see the data and agree with it.
I feel better at90 than I do at 120.


A difference of .5 A1C really isn’t significant.
Other than that, which did you prefer??

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I don’t know whether you are using Sleep Mode 24/7 but that can improve average numbers. At the same time, Control IQ will reduce your insulin if you are projected to be below 110 and will suspend your insulin if you are projected to go below 70. Sleep mode allows for lower averages than regular Control IQ although you don’t get automatic boluses. But the fact of the matter is that the Control IQ algorithm is not designed to allow a target of 80-90.

Some people game the system and claim to run flatlined at 90 overnight. That would not be possible for me and I truly don’t understand how they do it. Long insulin reductions and suspensions always result in sticky highs for me.

Interestingly my A1c’s with Control IQ are not higher than my previous A1c’s. But I don’t find it to be less work than my previous regimens. But it is a safer regimen because I rarely have lows below 70 with Control IQ.

I have tried many things to love Control IQ. One is using the Untethered Regimen where I take one or two injections of Lantus per day to ameliorate post insulin-suspension highs. It does help and that is what I am doing currently. But it doesn’t magically improve my numbers that much and mostly I am doing it now because we have a series of grandchildren spending spring break with us in Arizona and it is easier to spend hours swimming with them without my pump when I have a background long-acting insulin.

My second strategy is to turn off Control IQ during the day and that increases my range of acceptable blood sugars from 110-120 per Control IQ to 70-120. This strategy works for a while and then I start getting a lot more lows. And I don’t believe that numbers in the 50’s and 60’s make me healthier just because my A1c might go down.

Ultimately I believe that the Achilles Heel of automated insulin systems is the speed of insulin. If the post-reductions and -suspensions of insulin weren’t followed by sticky highs, these systems would be great. But it takes a long time for insulin to start working to prevent those highs.

Having been diagnosed in 1976 before home BG monitoring and newer insulins, I truly appreciate the incremental steps to keep those of us with diabetes healthier. Control IQ is one step forward and I look forward to many more steps forward.


I appreciate reading about all the Tandem individual approaches though I confess the variations scare me a bit. I am finally ordering one tomorrow or Thursday. It sounds like a lot more work than I want but I truly need the “safety” of avoiding lows. I hope I can just get good training and start out with “their way” until I am comfortable with it. and I hope it will work for me. But I have a bunch of supplies for my 630. Darn it! Oh, and I don’t want a 5 a1c. The mid 6s are ok for me. Again, I can’t read too much about the experiences of those who are testing and reporting the C-IQ system.

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Enjoy it and don’t be afraid to experiment. (Make only v e r y. t i n y changes to parameters).

My A1C improved slightly with the pump: from about 6.5 to 6.3%

I’ve noted this elsewhere but the biggest bang for my buck was Dexcom. My A1C had been climbing in the past few years with multiple daily finger pricks and multiple injections, to a high of around 8.4%. And no matter what I did, I couldn’t get it lower. I had many lows although in 30 years only one where I needed to go by ambulance.

Anyway, Dexcom made an immediate and dramatic difference: all my A1Cs for the past 18 months have been 6.3-6.5. Even lower more lately as I’ve figured out the pump, and with fewer lows.

The pump made a difference in that I don’t need to carry as much crap with me all the time and I much more rarely need to snack to address a pending low. I don’t spend as much time going high either. My nights are fantastic. I average one alarm a day, usually wgdd we n trending low but very rare to see “urgent low”. In general, 1% low, 10% or so high, and 2% very high. Not perfect but I live a pretty unimpeded life: I work, ride a motorbike, ski, bike, hike, camp, I eat largely what and when I want (just not too much pie or chips) and hope to enjoy as much of the rest of my time on Earth as I can.


I am hesitant to be a “sleep walker.” That’s my trainer’s phrase to describe those who use sleep mode 24/7. Looking at the trends during my sleep period, it is pretty up and down. Sometimes as high as 145mg/dl and down to the low 90s. It is certainly not the fairly flat curve I had with Lantus.

I don’t know if my endo and/or insurance would cover Lantus for me. I have one unopened pen and vial of Lantus that I keep for emergency use for a pump failure, but @Timothy ‘s post is interesting. If I were to have site problems it would be from basal, my ratio is near 70% basal to 30% bolus.

Thanks for your answer, it’s a learning experience.

Well the pump is easier to live with. On MDI I was doing a minimum of 6 injections per day, more if I did any corrections. I like that I use up a vial of Humalog in 20 or so days. Because I didn’t use a lot basal, a pen would still have 45% left at 28 days. Because of getting insulin every 90 days I would toss those pens away with a guilty heart. There is only so much room for diabetic stuff. I’ve got fridge space and 2 “D” draws plus a pill drawer.

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I spent my whole life being a data analyst. I weigh trends as more important than static numbers. The problem is, with us humans, there are so many variables, food for example.

I eat pretty much the same thing daily with about 115g of carbs. Since I got the pump, I have been a little adventurous, eating a lunch around 70g carbs. I would to an extended bolus of 60/40 with the 60% being enough for the 70g carbs. When I have done this I would have to add a correction to prevent an unacceptable spike. At least with the pump this is easier to do.

BTW I wouldn’t even attempt this with MDI.

Enough rambling from this old man.

Luis, I am on MDI and eat 275 carbs with a deviation of 19. It really can be done. I average 4 shots daily. I am very happy that you are finding success with a pump though!

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Can you provide examples?

I’m guessing lots of veggies vs breads/pasta type carbs. Slower carbs, with mix of fats/proteins works good for me.
I suspect some plant based carbs pass through as bulk, with minimal impact on BG.

Having an in range BG at start of meal helps too, or pre-bolus and delay before eating.

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For breakfast I eat 1/4 cup oatmeal, 1 cup blueberries, 1 medjool date, 1/2 banana

Lunch 1 cup quinoa, 1 cup beans, vegetables and a chocolate garbanzo bean cookie

Dinner varies maybe a soup or chili with beans and potatoes and a salad and 2 cookies.

I always have a pre meal glucose level around 80-100 and I usually pre-bolus. I almost always get on my exercise bike after breakfast and lunch.


You revealed your secret: exercise. I also noticed that exercise lowers BG much faster than insulin. I can stay 100% in range when I get on my elliptical for 5 minutes once I see my BG trending towards the upper target. It just takes a lot of discipline to do that.


I figure that there isn’t a downside to exercise!


Throughout all the years since diagnosis exercise along with diet have been a constant plus.

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Most people on a pump have some kind of long acting insulin in case of a pump failure. I was experimenting with it because it was getting close to expiring. But then I started reading about people who use it with a pump.


@Luis3 , there are a few things here. @Laddie was spot on in her comments.
[1] MDI allowed you to fly NOE (Nape of the Earth) [check the aviation term]
[2] CIQ automates and has higher levels. You reported levels in the 80-90 range. Even in sleep mode CIQ cruises at 112.5 to 120mg/dL.

Your experience is perfect and in keeping with the professional literature about the CIQ. One more question in two parts:

[1] what is the clinical harm done to you at 112.5-120mg/dL that is not present in the range 80-90?

[2] in the absence of clinical harm documented by you and your prescribing doc, is the effort necessary to reach 80-90 worth the effort?

If you really want to fly NOE with CIQ. It can be done.

Additionally, check the Facebook group “Tandem Diabetes Control-IQ Users’ Group”. There are many there with results like the above.


I used to be convinced that lower is better, but I’ve eased up.
I don’t think there is really any difference between 90 and 120 in the long term scheme of things.

I am able to maintain sugars in the high 90 s by taking 10 units of lantus every day along with my pump. My pump turns off basal insulin sometimes but the lantus keeps me from jumping up. I don’t take the lantus to keep my sugars lower, I do it to prevent stubborn highs, but it also lowers my average glucose.


First, Time in Range is replacing A1C for BG management for persons with diabetes using CGMs it is a truer measurement of quality of control.

A1C is NOT a reliable metric of quality of BG management. I compare it to cash flow . A1C is like your average salary. It does you no good between jobs.

If on average you have adequate annual income but your paydays are erratic you’re always living in uncertainty . You might be scrambling one day to pay bill, and a week later have a surplus. Your creditors would penalize you for your erratic payment schedule . You’d pay penalties and interest, have higher interest rates, and be less happy than if you paid off every bill in full on time, and so would your creditors.

Control IQ manages your insulin cash flow so you pay your sugar bills in full, on time. Your body is the creditor.

Any computer, no matter how simple, is only as good as the data it’s given. GIGO.

If it works from the same CGM as you, and if profile of ICRs, CRs, and basal rates are accurate for your “normal”, then Control IQ should be able to do a better job than MDI with one set of 3 numbers because it doesn’t get tired, distracted, sick or do faulty math. Plus there’s the positive effect that better sleep quality has on BG.

I held off on Control IQ until I had a profile that worked with Basal IQ, knowing that my sites aren’t reliable and I have to be able to tell if the system is working right and we ready to make corrections when it isn’t.

As a result my TIR is great, but man, was it a lot of work to get those numbers right. My spirit was willing, but my flesh was weak. Hopefully, Control IQ will be a good driver assist for my “vehicle”, and I’ll only need to handle breakdowns.


@Luis3, circling back after about 45 days. What did you decide? What was your solution?

Inquiring minds would like to know?

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