Even within a few weeks of starting on Control-IQ by Tandem Diabetes Care, I knew that this new system that helps automate insulin dosing was the right choice and could help me better manage my diabetes.

That high praise continues in 2022, more than 2 years after my introduction to this innovative diabetes technology, even though I have some suggestions for improvement.

The pop culture analogy that best describes my experience so far is that Control-IQ is like Baby Yoda — it’s cute and photogenic and has gone viral online. Sure, it has some mystical skills but it gets tired easily and can’t yet fully tap into “The Force” to keep me at optimal glucose levels all the time.

Some days with Control-IQ have been magical, while others left me wanting to throw the device to the floor. But there’s no arguing with the remarkable time in range (TIR) results I’ve achieved with Control-IQ more often than not: between 70 to 180 mg/dL at an impressive 90% of the time, up from the roughly 66% beforehand.

Control-IQ (or CIQ as some of us fondly call it) is one of the newest “closed loops” or automated insulin delivery (AID) systems, which connect an insulin pump, continuous glucose monitor (CGM), and control algorithm. These pieces create a system that can mimic what a healthy pancreas does, by monitoring glucose levels and delivering insulin as needed.

The Food and Drug Administration (FDA)’s approval of CIQ in December 2019 was big news for the diabetes community. It became one of the most advanced diabetes technology commercially available, aimed at reducing the number of low and high blood sugars one experiences.

Specifically, CIQ combines Tandem’s touchscreen t:slim X2 insulin pump with the Dexcom G6 CGM via an algorithm that auto-adjusts insulin doses to help keep blood sugars more in range. Its set range is 70 to 180 mg/dL, but it works hard to keep you as close to 110 as possible, using a variety of methods.

It’s not a silver bullet, to be clear, but it’s focused on helping you do better and “think less” about the traditional ups and downs that diabetes presents each day.

Users still have to take insulin bolus doses for meals, because the system doesn’t automatically do that. But the auto-correction function can help reduce high blood sugars more quickly if you miss a meal bolus or miscalculate. This is a huge advantage for most of us whose carb-counting skills are far from perfect, making mealtime insulin doses hit or miss.


  • The Tandem t:slim X2 pump is compact and attractive.
  • The pump allows you to enter carbs and insulin correction data.
  • CGM data is displayed on the pump home screen, with various time views.
  • You can view pump and CGM data through both the Dexcom G6 app and the Tandem t:connect app on compatible iOS and Android smartphones.
  • CGM does not require fingerprick tests for calibration, but the pump and apps allow you to enter fingerstick readings if you choose.
  • You can program a variety of different basal rates and correction settings.
  • The device offers optional “Sleep” and “Exercise” modes to help you fine-tune glucose targets during certain times of the day.
  • Users report excellent accuracy and improvement in glucose TIR.


  • You have to wear two devices attached to your skin in different spots: the CGM and insulin pump infusion site.
  • The pump requires charging once or twice per week.
  • The first generation of Control-IQ has a fixed glucose target of 110 mg/dL that some feel is too high.
  • The system runs on Dexcom G6 readings, so if the CGM sensor or transmitter is not working correctly, the automated features will be impaired.
  • There’s a three-button procedure required to unlock the pump home screen (for safety reasons).
  • Some report that physical activity or dropping the t:slim X2 results in a cracked or shattered touchscreen.
  • The clips for Tandem’s pump are poorly designed and don’t stay attached to a waistband or beltline.
  • It’s expensive — cost may be a barrier for some, even with insurance coverage.
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The system is cleared for kids as young as 6 years old, and adults with either type 1 or type 2 diabetes. Here is a look at the basic features on this system.

Touchscreen and sleek design

The Tandem t:slim pump is the first to feature a touchscreen, giving it an Apple-esque look that feels more modern than most insulin pumps. Honestly, with its colorful app interface, it feels like a cool piece of tech rather than just another piece of medical equipment.

You can also decorate your pump with “skins” to show off your style. The CGM data is displayed directly on the t:slim X2 pump touchscreen with all the typical graphs and displays showing the current glucose level, plus data going back 3 to 24 hours.

Remote upgrading

The system uses the t:slim X2 insulin pump platform that was the first to allow remote product updating from home, so you don’t have to trade in for a new piece of hardware every time some functionality gets upgraded. You just access Tandem’s t:connect customer portal to activate the upgrade.

No routine fingersticks

Since this system uses Dexcom’s latest G6 CGM model, it does not require additional fingersticks for calibration per the FDA as previous CGM generations did. However, you can still choose to do backup fingersticks if preferred.

Pump charging

You’ll need to charge the t:slim X2 pump using a micro-USB cable provided with the pump. Tandem tech support recommends topping it off each day for 10 to 15 minutes, even though you could likely go several days without charging if necessary.

You can also order extra cables to keep at home, in your car, or at work. Many people recharge their pumps briefly when it’s disconnected for showering, or every few days when they change infusion sets and the insulin cartridge and tubing.

Auto insulin shutoff and resume

Control-IQ automatically shuts off insulin delivery when the CGM predicts that your glucose level will drop below 70 mg/dL or if your glucose is below 80 mg/dL and falling. Instead of automatically stopping delivery for a set period, the system immediately resumes insulin once your glucose values are repeatedly back in range and rising again.

Auto basal adjusting

Amazingly, Control-IQ can auto-adjust basal rates to help keep your levels in range — both on the low and high end of the glucose spectrum. The smart algorithm behind this feature was acquired by Tandem Diabetes years ago from the startup TypeZero Technologies (before Dexcom acquired TypeZero).

Glucose target ranges

Control-IQ is programmed with a variety of target range settings that differ in part by time of day:

  • The regular target range is 112 to 160 mg/dL, where it maintains your pre-programmed pump basal rates.
  • If the CGM predicts you’ll rise above 160 mg/dL in the next 30 minutes, it will increase your basal rates.
  • If your glucose is predicted to go above 180 mg/dL in the next 30 minutes, it will automatically deliver a correction bolus — but only 60% of what your pump settings dictate, with a target of 110 mg/dL.
  • The optional Sleep Activity mode allows a more aggressive range of 110 to 120 mg/dL. This optional setting does not allow any auto-correction boluses while it’s activated, and you can set specific times overnight or just leave it on for the tighter range.
  • An optional Exercise mode allows for a target of 140 to 160 mg/dL.

Auto-correction boluses

Like most insulin pumps, the t:slim has a built-in bolus wizard that helps you calculate doses for meals based on your blood sugar correction and insulin-to-carb factors.

On top of that, the Control-IQ system offers an auto-correction function that can help reduce high blood sugar quickly. So, if your glucose is predicted to go over 180 mg/dL, it will trigger a bolus that is about 60% of the calculated correction amount, with a target of 110 mg/dL.

This works on top of the self-adjusting basal rates already in play. Control-IQ doesn’t automatically make boluses doses for meals (users still have to do that) but this auto-correction function can help reduce high blood sugars more quickly if a meal bolus is missed or calculated incorrectly.

Optional sleep and exercise modes

The optional Sleep Activity mode allows a more aggressive range of 110 to 120 mg/dL. This optional setting does not allow any auto-correction boluses while it’s activated, and you can set specific times overnight or just leave it on for the tighter range. The optional Exercise mode allows for a target of 140 to 160 mg/dL.

The first version of Tandem’s t:connect app came out several months after Control-IQ. This app works on iOS and Android smartphones, though only certain phones are compatible.

The app links to the t:slim X2 pump and allows you to see your glucose readings, insulin on board (IOB), basal rate adjustments, auto-correction boluses, CGM transmitter status (battery life and time started), as well as your TIR for the last 24 hours. Your data can also easily be shared with up to six people.

In 2022, Tandem launched the second version of its t:connect app, allowing you to dose insulin directly from your smartphone. It also included several other feature updates, including alarm changes and what icons appear on the smartphone app screen. That update requires a new app update, as well as a 30-minute training.

However, only a few iOS and Android smartphones were compatible as of August 2022. More are being added as the company gets them cleared by regulators.

Eventually, Tandem plans to launch another mobile app update which will allow for full pump control from the smartphone app. That is roughly expected in 2023.

I found the upgrade process quite simple:

  1. I logged into the t:connect portal online. This started a 5-step process confirming my Dexcom G6 use and receipt of my doctor’s prescription.
  2. With all that confirmed, I was ready to start the training — an interactive program in two parts that took 40 minutes for the first part and 20 minutes for the second. It provides periodical quizzes and prompts like online traffic school or employee training that many do online these days.
  3. After completing those modules, I got an authorization code that allowed me to proceed with the update to my t:slim X2 — going from Tandem’s previous Basal-IQ system to the new Control-IQ feature.
  4. The system prompted me to load a new insulin cartridge and start a new CGM sensor session. Fortunately, I didn’t lose the existing G6 sensor I was still wearing. After a brief warmup period (not the full 2 hours typically required for a new G6 sensor), it started generating CGM data on the t:slim X2 screen.

Important: Once you update from Basal-IQ to Control-IQ, you can’t go back to the earlier version. So for anyone who isn’t sure about updating just yet, think twice before making the switch.

As time went on and new updates or app versions were released, I had to go through periodic online training sessions to confirm these changes. That usually required me to use the Tandem Device Updater tool, a simple process complete with easy-to-understand prompts and instructions.

With any new smartphone, I’ll need to go through this process to ensure my new phone is ready to use with the Tandem technology.

As noted, the system helped me obtain some impressive results that I hadn’t been able to achieve before starting on this tech. It also provided new lessons about how much insulin I’m using overall throughout the day and helped me pinpoint how my food and drink choices impact my glucose levels.

I’m not a statistics-savvy person, but it’s still fascinating to see that in my first 2 weeks with Control-IQ that the system adjusted my basal rates 1,794 times, with 98% of those being auto increases or decreases and only 24% being insulin suspends.

Of my total 102 bolus doses delivered (average six per day), 23% were corrections and 11% were “extended” doses to cover complex meals. I used the bolus calculator for 47% of my mealtime dosing, and the rest were delivered automatically via Control-IQ.

  • Lows are 1 to 2% of my readings, about the same as before.
  • Highs are dramatically reduced, down from 33% of the time to only 13%.
  • Sleep is improved because the lows are predicted ahead of time and cushioned (if not fully prevented), while the system automatically corrects to avoid highs overnight.

Sometimes I do get rebound highs that the system just can’t handle. For example, when I tried out Exercise Mode for the first time while shoveling Michigan snow, but also added a blueberry muffin into the mix.

I went high thanks to that muffin and the exercise adrenaline boost but eventually bottomed out from the delayed snow-shoveling effect. And my rescue carbs ended up being too many Girl Scout cookies… no surprise that I ended up in the 300s with CIQ chugging uphill to catch up.

No diabetes tech can yet deal with those monkey wrenches thrown into the mix.

By motivating me to follow my data more closely, Control-IQ teaches me lessons about exercise routines and sleep patterns.

It helped me to step back from over-treating when my glucose levels go low — because, under typical circumstances, the basal adjustments and auto-shutoff curtail insulin delivery and help me recover more quickly without stuffing my face.

Some features I find especially helpful are:

1. Retention of extended boluses

With the prior system, an Extended Bolus got canceled if you went low during that scheduled bolus. Now, Control-IQ allows you to continue delivering the rest of a programmed Extended Bolus if you desire.

2. Delay of insulin restart

This system also does not immediately resume delivering insulin once CGM data signals that your glucose levels have started to rise after a low. Rather, it takes a moment to assess three of your past four readings (so 15 minutes of data) to make sure you are rising before it kicks basal delivery back into action.

3. Exercise and sleep activity modes

These two optional activity modes are interesting, and I have learned that you can use them in ways other than what the manufacturer intended. For example, I am using the Exercise mode overnight to shoot for a higher target range of 140 to 160 mg/dL to avoid lows.

The system will still administer an auto-correction dose if needed overnight. And vice-versa: I have been using Sleep Activity mode for those times during the day when I’m pretty steady and would rather not have any auto-boluses delivered.

Several items jump out at me for needing improvement.

1. Display colors and icons

One of my biggest gripes about Control-IQ so far is the use of tiny icons, which are tough to see on the pump touchscreen:

  • a diamond icon in the top left corner of the screen, signaling that the system is turned on and in use
  • a letter “B” in a box at the top right corner, signaling the current basal activity

Both icons change colors slightly depending on what the system’s doing — orange if basal is decreased to different shades of blue and an insulin drop icon if insulin’s increased or a bolus is being delivered.

I am partially color-blind, so I have trouble differentiating the varying hues of these icons. I’d like to see these icons larger and designed more intuitively to reflect a particular status — like maybe a plus or minus symbol next to the B, reflecting a higher/lower basal rate.

2. Better detail on adjusted basal rates

Likewise, to discover whether the system is increasing or decreasing basal rates, you have to touch that little B basal icon in the top screen to get to a “Current Status” menu that displays the current basal rate being delivered. It doesn’t tell you how much that basal rate differs from your pre-programmed basal rate for that moment.

It would be much handier to have the programmed basal rate displayed right above or below the adjusted rate, so you could understand how it’s adjusting to your needs.

3. Slow reactions require patience

The biggest lesson for me is that Control-IQ doesn’t react to big changes quickly. That, along with the slower action of the Novolog insulin in the pump compared to the inhalable Afrezza insulin I’d been using previously means I have to remind myself to be patient and let Control-IQ do its work before over-reacting and manually delivering more insulin.

4. Dexcom is the weakest link

This hurts to write because I have long been a fan of Dexcom’s CGM over anything else available. But unfortunately, the G6 hasn’t performed well for me. I get lots of instances when the signal disconnects, making it unreliable.

Also, I have used G6 according to product guidelines but have rarely had one of these 10-day sensors actually last that long. Only a handful of my sensors have lasted the full 10 days. On average, I get 6 to 7 days per sensor before it malfunctions and stops the sensor session. This means I must repeatedly call in each of those early failures to Tandem or Dexcom to have my sensor replaced.

If others are experiencing these issues with G6 sensors, this could be a major disincentive for patients to turn to Tandem’s Control-IQ system.

The retail price of the Tandem t:slim X2 pump with Control-IQ is $4,000.

That is quite expensive. But Tandem says health insurance typically covers 80% of that cost. That is what I found with my employer-provided insurance plan.

Supply cost

Remember, you still need to purchase all the Dexcom G6 CGM supplies separately. While insurance coverage may vary, the retail price would be $237 for a single G6 transmitter that lasts 3 months and $349 for a box of three 10-day sensors.

The Tandem t:slim X2 operates as the “receiver” connecting to the G6, so you don’t need to purchase a separate CGM receiver. If you don’t go through insurance, you can order Costco’s lower priced CGM supplies if you qualify.

ProductManual calibrations?Insulin pump tubing?Auto-corrections?Phone control
Tandem Control-IQnoyesyesbolus only
Medtronic Minimed 770Gyesyesyesno
Omnipod 5nononofull phone control

Some people with diabetes have chosen to build closed loop systems using the Dexcom CGM, certain insulin pump models, and an open source algorithm (either OpenAPS or Loop). Once set up, these do-it-yourself systems work almost exactly like the Tandem or Medtronic systems, but they do require a lot of time and trial and error. They’re also not FDA-approved.

Finally, there is the new Bigfoot Unity automated insulin delivery system that was cleared by the FDA in May 2021. Unlike Tandem Control-IQ its competitors that all use an insulin pump, this new system is designed for users who manage their diabetes with multiple daily injections (MDI therapy). Bigfoot Unity may offer an attractive alternative for those who want the power of a closed loop system without the need to wear a pump device.

Here are answers to a few key questions we’ve heard about this new technology:

What if you have ’tight‘ diabetes control already?

It is true that as a first-generation automated system, Control-IQ has some limited fixed settings, including the 112 target. If you’re aiming for tighter control, you might want to adjust that number downward. I am OK coasting between 100 and 150 most of the time. If I wish to run tighter, it’s easy enough to temporarily adjust my basal and correction settings to more aggressively push me lower.

Does Control-IQ have a set 5-hour insulin duration?

Yes, it does. Control-IQ doesn’t let you change this. It’s a fixed setting of 5 hours for how long the insulin will remain active in the pump’s IOB calculations. It’s a longer active period than many are used to, but Tandem says they chose this to allow the algorithm to deal with simultaneous calculations for potentially multiple insulin doses. I haven’t experienced any negative impacts from this.

How does Control-IQ compare to Medtronic’s Minimed 670G?

Wil Dubois, a longtime type 1 and former clinical educator used Medtronic’s 670G and Tandem’s Control-IQ. He shares this perspective:

“Both systems did a good job of controlling blood sugar globally and keeping the pumper in reasonable range most of the time, (but)… Control-IQ is more robust than the Medtronic product. I never had the Tandem pump fall out of auto-mode, except when a new sensor was spooling up. All in all, I found Control-IQ to be significantly less of a burden, in terms of life interference. […] Plus, not only was my overall sugar in better range, most mornings I woke up with an excellent BG around 100 mg/dL, lower than the typical 140s I was seeing on the 670G.”

This technology is pretty awesome. Sure, it’s not perfect because no diabetes tech can make that promise. But seeing improved TIR has been enough to make me a fan, despite its flaws. And if the quality of life improvements have got me feeling more in tune with the “Diabetes Force,” then it’s a win to me. I’m excited to keep using Control-IQ and see how it grows up with new features as we move forward.