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Image via Tandem Diabetes Care

Tandem Diabetes Care, makers of the t:slim insulin pump, once appeared like it might be the latest diabetes device manufacturer to go bust. But the San Diego-based medtech company made its way back to solid footing and now has one of the hottest lines of diabetes products available.

Helping to make that happen was their Basal-IQ technology, an exciting software feature built into the t:slim X2 insulin pump that predicts blood sugars and automatically adjusts insulin doses to ward off hypoglycemia and keep glucose levels in range.

Tandem received regulatory approval from the Food and Drug Administration (FDA) for Basal-IQ in June 2018, and launched it later that summer. The much-anticipated system connects the touchscreen t:slim X2 pump with the latest Dexcom continuous glucose monitor (CGM) to provide glucose prediction and automatic insulin shutoff when a low glucose is predicted. Importantly, it capitalizes on the t:slim X2’s ability to be remotely updated from home, so that new features can be incorporated without a need to buy a whole new pump every time a new function or feature is introduced.

“I’m finding that it adds a whole new level of CGM integration and control that we’ve never seen before,” longtime type 1 writer and DiabetesMine columnist Wil Dubois said about Basal-IQ, after first test driving the new system.

He described it as “crazy wonderful most of the time,” and noted that the system includes “a lovely, brilliantly designed pump — both physically, and perhaps more importantly, in its programming. Still, [it’s] not perfect.”

Here, DiabetesMine sums up the features, pros and cons, user experience, and pricing details of this partially automated insulin delivery (AID) system.

(Note that Tandem Diabetes Care has an even more advanced AID system known as Control-IQ, but some users prefer the features of Basal-IQ. Read on to learn more.)

Tandem Basal-IQ is a system that integrates the Tandem t:slim X2 insulin pump with the Dexcom G6 CGM and the proprietary Basal-IQ algorithm designed to help keep blood sugars in range. As noted, the system can automatically shut off insulin delivery for limited periods if a low blood glucose is predicted.

It does this in two cases:

  • when you go below 70 mg/dL
  • when its algorithm predicts that you will go below 80 mg/dL within the next 30 minutes

For both situations, Basal-IQ automatically resumes insulin delivery again when your glucose level begins to rise again. It uses three of the past four readings to trigger that auto-shutoff, and the main screen displays red swatches to indicate when and for how long Basal-IQ has shut off your insulin delivery.

Users can choose whether or not they want alerts to sound each time insulin delivery is suspended. This allows you to have Basal-IQ keeping you safe in the background if you choose, with fewer alerts and alarms to disrupt your life (helping to address diabetes device fatigue for some people).

The t:slim X2 insulin pump is the core of the system. It has the same form factor and basic look as earlier t:slim models that have been around since 2012. But what’s different is the 2016 addition of a remote updater feature that lets you upgrade the pump from home, just like you can with an iOS or Android smartphone. This was a first in the insulin pump market at the time, and it means you don’t have to buy a new piece of hardware every time some functionality or feature is upgraded.

Tandem’s pumps are unique in using a color touchscreen. For safety reasons, there is a three-button wake-up and confirmation series required anytime you want to use it. You need to tap on the touchscreen’s 1-2-3 buttons when displayed to unlock it, and then there’s usually at least one confirmation message for whatever task you are trying to accomplish when using the pump — whether giving yourself a mealtime or “correction” dose of insulin, entering a blood sugar reading or carb amount, or manually turning off insulin delivery for a swim or other activity.

Because this system is integrated with the Dexcom G6 CGM (which you wear on your body separately), the pump display also shows a CGM icon and data.

You can press the silver “T” button on the top of the screen to wake it up and see the very nice, full-color CGM status screen for glucose data, battery and transmitter status, as well as insulin on board (IOB, or the active insulin) and the volume of insulin inside the pump at the time.

The default view of CGM data is 3 hours, but you can also scroll through 1-, 6-, 12- and 24-hour trace screens without needing to repeat the three-button unlocking sequence.

While many in the diabetes community have described the Tandem t:slim X2 as a sexy, easy-to-use device compared to others available, there are minor issues that some find irritating when using this insulin pump:

  • Large amount of insulin needed. You need at least 50 units each time to fill the cartridge, and then you need to push at least 10 units through the tubing to prime it.
  • Possible leakage. The little pig-tail part of said tubing is unique to Tandem, and for years t:slim insulin pumpers have complained that the twist-and-connect design leaves open the possibility of leaking insulin or introducing air bubbles into the tubing.
  • Multiple confirmation alerts. In order to unlock and use the touchscreen, you have to go through a confirmation screen each time. Those with larger fingers or difficulty with finger movements might miss their target and — thanks to a “3 strikes rule,” where the screen locks if you touch an inactive part of it three times in a row — have to start over by unlocking it and hitting all the buttons again.
  • Fixed alarms. Several of the pump alarms cannot be silenced or turned off, including “empty cartridge.” So, if you have a tendency to take a break before you start a new pump session, this alarm will beep constantly without any option to quiet it, which can be very annoying.

The CGM that powers Basal-IQ is the Dexcom G6, the latest generation of that company’s device as of 2021. To use Basal-IQ, you need to purchase Dexcom G6 supplies and Tandem pump supplies separately.

The G6 leads the CGM market, and get high marks for comfort, accuracy, and ease of use.

It is FDA approved for direct insulin dosing decisions, meaning there’s no need to take a confirmatory fingerstick glucose test before making insulin dosing decisions. It also self-calibrates, but you do still have the ability to manually calibrate it by plugging in a fingerstick result if you want to.

The Dexcom G6 sensor is labeled to last on the body for 10 days. As a Basal-IQ user, if a sensor fails early before the 10-day mark, you can contact either Dexcom or Tandem support to get a replacement sensor.

Note that some users have reported that the Bluetooth connection between the t:slim X2 insulin pump and the Dexcom G6 transmitter isn’t always reliable. Lost connections seem to sometimes happen when the insulin pump is positioned on the opposite side of the body as the Dexcom G6.

Tandem launched its mobile app in 2020, allowing users to see their insulin pump and CGM data and view many features of the Tandem system they’re using (Basal-IQ or the more advanced Control-IQ).

While the Tandem mobile app doesn’t yet allow for smartphone control of the t:slim X2 as of September 2021, Tandem is working with the FDA to eventually gain approval for that feature.

Basal-IQ also works with Tandem’s t:connect software for data analysis and data-sharing. You can share information with your diabetes care team, who are able to log directly into your account (with your permission) and view your data to help in your diabetes management.

Of course, what you really want to know is how well this partially automated system works to control blood sugars.

Clinical study findings are largely positive and impressive. This 2018 study showed that the predictive low glucose suspend capability significantly reduced hypoglycemia without rebound highs, for both adults as well as children with type 1 diabetes. Notably, that research showed 99 percent of the study participants finished the study — a big difference compared to the competing system at the time, which saw fewer people finishing the clinical trial because of accuracy and usability concerns about that competing technology.

In a 2019 study, researchers looked at data voluntarily submitted by over 5,000 Basal-IQ users and found that most reported high levels of satisfaction, trust, and usability. It also helped them sleep better and achieve better diabetes management overall.

DiabetesMine’s Dubois reported that for him, the system was “pretty remarkable” and “crazy wonderful” at keeping his blood sugars in check. However, he did note that it didn’t always catch “coasting Lows,” the ones where you’re steadily dipping lower over the course of several hours.

DiabetesMine’s Mike Hoskins also tested Basal-IQ, and noted that it “effectively cushioned the blow of hypoglycemia without eliminating lows completely.” In his initial review, he wrote that “thanks to the predictive auto-suspend feature, I’ve avoided plummeting into a situation where I need help. This is huge, and I’ve noticed that with continued use, Basal-IQ has started giving me more confidence to sleep through the night without fear of dangerous, severe hypos. Because I don’t feel the symptoms of lows much of the time overnight (aka hypoglycemia unawareness), this is a big deal for my wife and I.”

Others in the diabetes community have echoed those thoughts, including Connecticut D-Mom Samantha Merwin, whose son Logan participated in the Basal-IQ clinical trials. She told DiabetesMine that it was “truly a miracle for us,” particularly overnight when her son could wake up and see how many times the system had suspended his insulin while he was sleeping.

Another early adopter, Brian Mozisek in Texas, told DiabetesMine that he particularly liked how Basal-IQ offered him an ability to prevent low blood sugars during his high levels of activity and exercise. Mozisek said it helped him more aggressively tweak his settings, and watch for higher blood sugars that Basal-IQ can’t address.

Of course, every diabetes device has its drawbacks, as users quickly discover. Here are some that have been flagged by seasoned Basal-IQ users:

False lows. The Dexcom G6 — just like any CGM sensor — can generate inaccurate readings at times, such as if you’re sleeping on the sensor and triggering what is known as a “compression low.” This can result in Basal-IQ falsely thinking it needs to shut off insulin delivery. The sensor reading will readjust to accuracy after you take the pressure off it.

Repeat data entry. You must manually enter CGM sensor glucose values into the pump before delivering any correction boluses for higher blood sugars. On one hand, it makes sense since Basal-IQ only adjusts insulin for lower glucose levels. But it’s a bit of a head-scratcher since the t:slim X2 is connected by Bluetooth to the Dexcom G6 CGM and has full access to that data.

Low dosing lock. If you’re low and Basal-IQ has suspended insulin and you want to eat, you can’t layer on a dose of insulin for the carbs you’re consuming. Yes, you may currently be low or at risk of going low, but if you’re about to eat a banana split, it would be a good idea to deliver some insulin to cover it, in order to prevent a rebound high.

Snooze mode cancellation. If you are not interested in using Basal-IQ’s predictive capabilities, you can scroll to an option to turn off the auto-shutoff feature for a period of time. But if you had started an extended bolus before activating this Snooze Mode, Basal-IQ will also cancel any remainder of that extended bolus.

No scheduling profiles. There’s no automatic way to switch between basal (background insulin) profiles. This means if you’ve set up a special weekend profile, you cannot set it to kick in at midnight on Fridays. Rather, you have to remember to activate it manually.

As noted, Tandem’s newer and more advanced Control-IQ system can adjust insulin delivery for BOTH low and high glucose levels, and it offers a number of other features to improve one’s glucose Time in Range. That system was FDA-approved in 2020.

What’s important to know is that while both Basal-IQ and Control-IQ use the foundational t:slim X2, you cannot go from Basal-IQ to Control-IQ and then go back. Regulators don’t allow for that, meaning if you have a Basal-IQ pump and then update it to the more advanced software, you’re unable to revert back to the older Basal-IQ version.

There are pros and cons to both systems, and some users have shared that they were less happy with Control-IQ than they were beforehand because Basal-IQ offered more flexibility in fitting with their lives. Make sure to do your research ahead of time before deciding on one or another. You can read DiabetesMine’s full review of Control-IQ here.

Affordability is one of the big drawbacks for any insulin pump, especially one that is tied to using CGM data.

You can purchase the t:slim X2 insulin pump on its own, but the whole point of Basal-IQ (and Control-IQ) is having access to the automation, and that requires you to also have a Dexcom CGM. That means you must purchase not only the Tandem t:slim X2 and supplies, but also the Dexcom G6 system. It can be quite costly, even with insurance.

The Tandem t:slim X2 pump needs to be purchased directly from the manufacturer, but the Dexcom CGM and its supplies can be purchased through third-party distributors like Edgepark or at retail pharmacies across the United States, including CVS, Rite-Aid, and Walgreens.

Without insurance, the Tandem t:slim X2 pump alone has a retail price tag of $4,000, but with private insurance some plans will cover almost 80 percent of this cost. For the Dexcom G6 CGM, when you factor in the 10-day sensors and the 90-day transmitters, our estimate of the annual cost of use is $6,000 per year, or $500 a month.

Make sure to check on timely discount programs the manufacturers may offer, as well as checking with your own insurance for coverage specifics.


As of 2021, Medtronic is the only other company that currently offers a partially automated insulin delivery system in the United States.

Medtronic’s MiniMed 770G also combines a Medtronic insulin pump and Medtronic CGM with a controlling algorithm and apps that allow you to track your glucose levels and see pump data. It addresses both high and low blood sugars, like the Tandem Control-IQ version. One advantage may be that Medtronic is the only company that makes both insulin pumps and a CGM, so you only have to deal with a single manufacturer. The downsides are that Medtronic pumps are more “old school” design with no touchscreen, and many reviewers say their CGM is far less comfortable to wear than the Dexcom.

Beyond insulin pumps, there is the Bigfoot Unity automated insulin delivery system cleared by the FDA in May 2021. This system integrates an insulin pen with a CGM, providing many of the advantages of a connected system to users who manage their diabetes with multiple daily injections (MDI therapy).

Finally, some tech-savvy people in the community have chosen to build their own automated insulin systems using the Dexcom CGM, certain insulin pump models, and an open source algorithm (either OpenAPS or Loop). Once set up, these DIY setups work almost exactly like the Tandem or Medtronic systems, but they do require a lot of setup time, trial and error, and their use is not FDA-approved.

Most who’ve tried Basal-IQ say that Tandem has a real winner here. But it’s important to keep in mind that this system only addresses half of the glucose management equation because it only reacts low blood sugars, not highs.

Using a partially automated system like Basal-IQ can be daunting for some people with diabetes, especially those who’ve lived with this condition for a long time and may feel that they’re being forced to give up their own control of their insulin regime.

Yet, after giving it a chance and learning some of the ins and outs of how Basal-IQ works, many have found that this is just the option they need to protect from dangerous low blood sugar events. For some, the online training modules offered by Tandem may be key to successful use.