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Lifting the Nighttime Burden: The Power of Control-IQ Technology

As I look back on my early years with diabetes, starting with injections and fingersticks at 12 years old, I marvel at how I made it through. Managing diabetes at night is critical for physical and mental health. But it’s also nerve-wracking, perplexing, exhausting, and frustrating.

I hadn’t appreciated the burden I’d been carrying until that burden was lifted.

In my first 14 years living with diabetes, I was given a basal insulin regimen and expected to follow it every night – regardless of what happened that day or week, how late I had eaten, or how much I had exercised. The assumption was something like this: “You are only sleeping overnight, so things are ‘consistent.’ The same night-to-night insulin dose should work fine.”

Six years ago, my eyes were opened to the insanity of this approach.

I took part in a research study of closed-loop technology, which was considered cutting-edge back in 2015. An algorithm called “DiAs” ran on a locked-down Android phone, received data from a Dexcom G4 continuous glucose monitoring (CGM) receiver plugged into a custom-made Bluetooth box, and communicated dosing commands to an insulin pump.

That study was my first hands-on experience with closed-loop insulin delivery and having my basal insulin doses automatically adjusted every five minutes based on my CGM levels. I still fondly remember my biggest takeaway from that study: At Night: Dear DiAs, You Are Way Better at This Than Me.

Automated insulin dosing was an overnight game-changer because it removed so much of the burden, guessing game, and unpredictable blood sugars. My sleep improved and waking up around 120 mg/dL nearly every morning (with less effort and worry) was incredible.

Closed loop also taught me a profound lesson about insulin needs: They can change a lot from night to night, even within the same week. That years-old paradigm, that one overnight insulin regimen can rule them all, began to seem truly crazy.

I have been using closed-loop systems for years now, and many weeks have that same pattern of inconsistency. I might need half as much basal insulin one night, twice as much on another night, and something in the middle on a third night. Of course, with at least 42 Factors that impact blood glucose, this makes a lot of sense. No two nights with type 1 diabetes are exactly the same.

Coincidentally, that study of DiAs was a precursor to the later studies of Control-IQ® technology that is now available on the Tandem Diabetes Care® t:slim X2™ insulin pump. This article builds on those early lessons I learned, looking into the nighttime results of using Control-IQ technology. What do we know about overnight time in range, as measured by CGM, from all Control-IQ technology study participants?

Sensor Time in Range Overnight

The plots below are taken from the adolescent/adult (14-71 years) and child (6-13 years) studies of Control-IQ technology that were published in the prestigious New England Journal of Medicine.

Percentage of Sensor Time Spent in Range (14-71 Years)


This graph shows time in range (70-180 mg/dL), as measured by CGM, by hour of the day. Unlike a normal CGM trace, higher values on the chart are better here – i.e., closer to 100% time in range. The Closed-Loop group (N=112 people with diabetes) is in blue, using a t:slim X2 pump and Dexcom G6 CGM with automated insulin dosing. Gray is the Control group (N=56) wearing the same pump and CGM without automation.

You’ll notice that throughout the day, the Closed-Loop group had a higher time in range, as measured by CGM, at every time point – with a particularly big advantage overnight.

Indeed, from midnight (left) to 6 AM, the average sensor time in range was 76% in the Closed-Loop group vs. 59% in the Control group. The greatest difference occurred at 5 AM where sensor time in range was an impressive 89% in the Closed-Loop group vs. 62% in the Control group. At 5 AM, the average glucose level was 139 mg/dL in the Closed-Loop group vs. 166 mg/dL in the Control group.

This overnight advantage for Closed Loop was even more pronounced in children (6-13 years old):

Percentage of Sensor Time Spent in Range (6-13 Years)

This is the same chart as above, showing sensor time in range by hour of the day across both study groups. Again, we see the huge advantage of Closed Loop overnight. The average sensor time in range from midnight to 6 AM was 80% with Closed Loop vs. 54% in the Control group. You’ll notice that at 6 AM, the Closed-Loop group saw sensor time in range above 90%!

Navigating Complexity

By adjusting insulin dosing every five minutes, as needed, an automated system can cope with night-to- night changes in insulin needs and enable more predictable sensor glucose values by morning. My sleep has improved. I approach bedtime with more confidence and less worry. I wake up without diabetes as the first thing on my mind.

I didn’t realize what a burden I’d been carrying all those early years with diabetes. I now appreciate the sheer complexity of overnight diabetes management. Sleep impacts my diabetes and diabetes impacts my sleep. For example, poor sleep generally causes higher blood sugars and more insulin resistance the next day. However, low and high blood sugars during sleep wake me up and cause poorer sleep. Such “circular causality” makes nighttime incredibly frustrating.

It’s nice to have some help these days!


Adam Brown has a compensation agreement with Tandem Diabetes Care. From time to time, we may pass along suggestions, tips, or information about other Tandem insulin pump user experiences or approaches to the management of diabetes. Please note, however, individual symptoms, situations, circumstances, and results may vary. Please consult your physician or qualified healthcare provider regarding your condition and appropriate medical treatment. Please read the Important Safety Information before using a Tandem Diabetes Care product.


Even with advanced systems such as the t:slim X2 insulin pump with Control-IQ technology, users are still responsible for actively managing their diabetes. Control-IQ technology does not prevent all high and low blood glucose events. The system is designed to help reduce glucose variability, but it requires that users accurately input information, such as meals and periods of sleep or exercise. Control-IQ technology will not function as intended unless all system components, including CGM, infusion sets and pump cartridges, are used as instructed. Importantly, the system cannot adjust insulin dosing if the pump is not receiving CGM readings. Since there are situations and emergencies that the system may not be capable of identifying or addressing, users should always pay attention to their symptoms and treat accordingly.

About the Author

Adam Brown

Adam Brown was diagnosed with diabetes in 2001. He is the author of Bright Spots & Landmines: The Diabetes Guide I wish Someone Had Handed Me (300,000 copies sold/downloaded). Adam served as a writer and Senior Editor at diaTribe.org through 2019.

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