Control IQ Tandem Diabetes with Dexcom G6

Control IQ with T-Slim X2 Tandem VS Looping (Open-APS)

As a Certified Pump trainer, I have had early access to Tandem’s latest software update with Control IQ. This post is about my thoughts, what I like, what I don’t like, and how Control IQ compares to OpenAPS looping. The purpose of this post (and all my posts) is to help you improve your management and find the right method that works for you. To watch a video of this article, click here.

I usually loop with Omnipod (off-label), but I wanted to try the Control-IQ with Tandem.

Before this experiment, I was using Open APS with Omnipod (off-label) also known as looping. Being off-label, this system has it’s quirks, but there are a couple features that I really miss while using Control IQ with Tandem. Before jumping into what I like and don’t like about Control IQ, I want to give a brief overview of how Basal IQ works.

To Use Control IQ

  • Control IQ only works with the Dexcom G6 CGM
  • All Basal adjustments are based on predicted CGM reading within 30 min.
  • Adjustments are also based on your personal profiles [therefore continue to switch between personal profiles as needed (for example weekday vs weekend)].
  • 110 mg/dL is the correction BG target with Control IQ
  • Treatment values for 3 activities that we will go into detail cannot be changed (aka you cannot set your own personal correction ranges)
  • The 3 activities are: normal, exercise, and sleep
Me, downloading the Control-IQ software update.

To use Control IQ you must have on the following…

  • Carbs set to ON
  • A Basal rate
  • A correction factor
  • Carb ratio
  • Target blood sugar (needed if control IQ is not in use – loss signal, in between sensor sessions, no Bluetooth)
  • Your weight and total daily insulin (needed to calculate max insulin delivery rate and total amount)
  • Connected to Dexcom G6 CGM (no other make or model of CGM works)

NORMAL ACTIVITY: The activity you are supposed to be the majority of the time… First off, Control IQ bases its basal adjustments off of your programmed personal profile(s). The Control IQ uses the Dexcom G6 CGM reading (it’s only integrated with Dexcom G6) to base if your basal amount should be increased and use a correction bolus, just be increased, no change at all, be decreased, or be completely suspended. The adjusted basal amount is based on what your CGM reading is predicted to be in 30 minutes. Below is the Control IQ tier system. Below explain what CGM values trigger basal adjustments.

  • ≥ 180 mg/dL: If CGM reading is predicted to go above 180 mg/dL within 30 minutes, there is an increased basal AND an Automated correction bolus (more about the automated correction bolus below).
  • 160 – 180 mg/dL: If CGM reading is predicted to go in this range within 30 minutes, basal is increased.
  • 112.5 – 159 mg/dL: If CGM reading is predicted to go in this range within 30 minutes, basal is not changed.
  • 112.4 – 70 mg/dL: If CGM reading is predicted to go in this range within 30 minutes, basal is decreased.
  • ≤ 70 mg/dL: If CGM reading is predicted to go below 70 mg/dL within 30 minutes, basal is suspended.
Basal Adjustments for Control IQ for the Tandem T-Slim X2 pump.


  • Increase basal and give automate bolus 180 mg/dL
  • Increased basal if predicted to go above 160 mg/dL
  • Decreases basal if predicted to go below 140 mg/dL
  • Stopped basal if predicted to go below 80 mg/dL

My thoughts on the Control IQ Exercise Activity. I don’t use the exercise activity often. The reason is that I typically exercise fasting so I have low insulin on board going into a workout which decreases lows. Also, I do a lot of HIIT workouts to increase insulin sensitivity and to keep in shape. Such type of workouts tends to be more anaerobically based which actually initially requires insulin, but then decreases insulin needs for the next 24 hours. The level of increased insulin sensitivity is based on the intensity and duration of the workout. So although this Exercise activity doesn’t work too well for me, it could be very beneficial for those who workout out later in the day or after a meal with a higher IOB. Steady-state cardio (think biking, jogging, swimming, dancing) tends to decrease your blood sugar after 15 min. Also the longer you perform steady-state, the more your blood sugar will drop. SLEEP ACTIVITY Sleep Activity Treatment values: the range is lower and narrower since there are fewer factors that will affect you during sleep.

  • Decreases below 112.5 mg/dL
  • Stop basal if below 70 mg/dL
  • Increase above 120 mg/dL
  • No automatic correction boluses

When enabling or scheduling sleep activity, you should plan on sleeping for 5+ hours so don’t use for naps Manual sleep activity or program sleep schedule, or you will have to enable and disable manually if you don’t input a sleep schedule. You can create two different sleep schedules for example weekdays vs weekends. However, for your health, keeping to a sleep schedule is ideal and can make your blood sugar control (and weight loss goals) much easier to achieve.

My Results while using Tandem vs OpenAPS Looping.

After this week with Control IQ, my average is higher than what I like. However there are less lows which is awesome.

Below are my results (Open APS compared to Control IQ).

OpenAPS Glucose Management Indicator: 5.8%

Control IQ Glucose Management Indicator: 6.2%

OpenAPS Average Glucose: 106 mg/dL

Control IQ Average Glucose: 119 mg/dL

OpenAPS Average Glucose: 36 mg/dL

Control IQ Standard Deviation: 31 mg/dL

OpenAPS: Above % / In Range % / Below Range % : 4%/93%/3%

Control IQ: Above % / In Range % / Below Range % : 96%/4%/0%

OpenAPS “Looping” VS Control IQ

Features I Don’t Like with Control IQ

My biggest complaint so far is postprandial blood sugar due to the pump not knowing carbs on board like with looping. The reason for this is that unlike looping, Control IQ software doesn’t not use carbs on board. Meaning that the Control IQ doesn’t have memory of the carbs you have recently eaten (at least not in a way that’s nearly as effecive as OpenAPS). This would be fine, if you didn’t have to use the CGM reading, but if you eat multiple amounts or do a prebolus, the Tandem pump doesn’t remember how many carbs on are board. For instance, I ate about 30 grams for lunch but was sitting at 82 mg/dL so my Tandem pump recommended a reduced bolus of 0.6 U.

I then “trying to be good” used the recommendation. I then decided to have an apple, so I added that I was now about to eat 20 grams, but because my blood sugar was still below target at 84 mg/dL, the Tandem pump did not recommend to give take the fiull amount of insulin, it actually recommended not to take any additional insulin although I know that the reverse correction with my first 30 grams consumed had already been taken into account.

Fast forward to an hour later I am sitting at 182 mg/dL with a diagonal up. This isn’t super high, but this could have been completely avoided.

ALSO, I couldn’t stand to not take anything for the apple so if I had completely obeyed the Control IQ suggestions, I would have been much higher. It recommended 0U, but I took 0.7U (usually I’m about 1U for an apple).

The other feature I’m not crazy about is the tube. I had used a medtronic 530G pump for years, so I thought tubes were just life as a T1D, but using an Omnipod with looping was definitely nice, especially during workouts.

Features I DO like with Control IQ

I like that the software works, all the time. Even if it isn’t nearly as aggressive as I would like it to be, I can count on a decent connection from my pump to my CGM so I can count on constant basal adjustments. With my closed loop Omnipod system, I would have to constantly close and reopen the app or toggle the rileylink switch to make sure the rileylink (device used to connect pod to phone) and phone were connected and working. It’s also nice not to have to carry an additional device (the rileylink), but I am now carrying a heavy Tandem pump. So that’s not a big change. I like the sleep feature. This allows for a tighter range, but doesn’t allow for the automated correction bolus.

However if your blood sugar is predicted to go above 120 mg/dL, your basal is increased. With normal settings, basal is usually increased if you are predicted to hit above 160 mg/dL.Oh, and I love that my CGM reading is already uploaded on the bolus screen which is new feature for Tandem, however this was already a feature for Omnipod looping system.

TAKEAWAY: The decision is ALWAYS what is best for YOU, your goals, and your management style. Overall I think for the masses, Control IQ could be a rather helpful tool, but for those who want really tight control, they will likely need to manipulate Control IQ (ahem, perhaps extend the sleep activity) or use Open APS looping. To be honest, Control IQ has worked much better than I anticipated. I thought I was going to use it for 3 days and be dying to have it off and back to my loop set-up, yet it’s been over a week, and I’m still with Tandem.

Frequently Asked Questions with the New Control IQ System?

Is my CGM number loaded in the bolus screen?

I’m glad you asked. YES! This isn’t news to DIY loopers or medtronic users, however for those who have been on Tandem, this is great news. So your CGM is preloaded on the bolus screen as long as you have the following.

  • You are in an Active CGM session
  • You have a Valid sensor reading
  • Trend arrow is working
  • Control IQ is turned on

What if I lose signal?

You’ll see a golf tee with a slash though it on the home screen. The default is to be alerted after 20 minutes of loss signal, which I think is a decent amount of time, however I think if you up it to 30 minutes, you’re still fine. If you lose signal, Control IQ will continue to work for 20 min, and if still hasn’t reconnect to your CGM, your basal will revert to your usual programmed basal settings. Remember to wear your pump on the side that you have your CGM so you have better connection and make sure to wear it out and away from the body to help with the bluetooth signal.

What About Temp Rates?

You can’t use a temp rate during Control IQ. You will get an alert that tells you to turn off Control IQ if you want to use a temp rate, however, you can still use an extended bolus, but only up to a 2-hour duration.

What about Insulin on Board (IOB)?

The IOB amount is different than with the previous version because it’s based on boluses from YOU, but also increases and decreases in basal from Control IQ. With the old version, IOB was strictly from blousing, not from basal. The IOB display time will not be turned on because on the continual fluctuating amounts from the adjusted basal, the automated correction bolus (if predicted to go above 180 mg/dL in the normal activity), and the bolusing from you (correction and food). Just too many factors that make the difference between bolus and basal too muddled.

What about Active Insulin Duration?

Related to IOB, with Control IQ the active insulin duration is fixed at 5 hours. This is to reduce stacking and research shows that we often put an active duration insulin amount shorter than what’s actually happening, which then of course, results in “unpredictable BG drops”. A common insulin action duration time used at training is 3 hours. As a diabetes educator, I understand how this can keep us more safe, but I don’t want this information freak you out. The majority of insulin used works in the first 90 minutes after injection, and most is used by hour 3, however the bigger the dose, the longer it lasts so the lasting affects depends on the person. So 5 hours if playing it safer. However if this increased duration keeps you from achieving your BG goals, especially relating to correction, consider decreasing your correction factor to make it bit more aggressive.

How does the automated correction bolus work?

An automated correction bolus only happens in the normal activity and is unique to Tandem (no other hybrid closed loop system currently has this feature). An automated correction bolus will only occur if your CGM reading is predicted to go above 180 mg/dL within 30 minutes.

How is the Amount of Automated Correction Bolus Calculated?

It’s 60% of your set correction bolus with the blood sugar target set at 110 mg/dL.

  • Amount is also based on
  • CGM reading
  • Correction factor
  • IOB
  • Predicted glucose value

As an important side note, the correction bolus amount will NEVER exceed max amount of 15 U/hr OR will not exceed 50% of your TDD within a 2 hour time frame.

How do I know if I have had an automated correction bolus?

  • White drop in blue square (next to status bar)
  • Bolus in bottom of the home screen
  • Pump history

You can view through your pump history with the following… Options ⇒ History ⇒ Pump History ⇒ Bolus You will also see it on your home screen when the automated bolus is occurring, but I don’t know about you, but I don’t exactly sit and watch my pump screen all day…

How do I know my current basal amount?

You can view what your current basal amount is by selecting the status screen (bars right about the total unit amount). Know the colors on the diamond in the left-hand corner of your home screen.

BLUE = increased basal

ORANGE = decreased basal

GREY = no change with a B in a blue box

RED= stopped basal with a “0” sign

The regular blue B by the status screen with a grey diamond means your usual basal is being used.

Blue in the diamond with a white drop with a blue background (right hand upper corner) means than an automated correction bolus has occurred.

It’s quite intuitive, so don’t stress about this. Also, you will have training before going onto this system if you are worried.

How do I turn Control IQ off? You can toggle Control IQ on and off. Options ⇒ My Pump ⇒ Control IQ ⇒ (toggle on or off)

Can I stay in sleep activity

ALL day?

Short answer. Yes. You can technically set the sleep activity all day. However, this is not the intended use and you may not get the full functioning system if you go this route. If you chose to stay in sleep activity, do so with caution, and as always, let your doctor/diabetes educator know.

Personally, I have been using sleep activity, all day, and have had tighter control, but I would never blindly recommend someone to do this without knowing the person and their situation. By sticking to sleep activity all day, I stay between 100-150 mg/dL. Which isn’t as tight as OpenAPS, but it’s how I can stay with Tandem and not have to deal with all the micromanaging for the tech bugs and necessary app reinstalls.

Also, during sleep activity, it uses a less aggressive algorithm to bring you back down to the target range since (12.5 – 120 mg/dL) since there isn’t automated correction bolusing during sleep activity. With this said, attention to detail to exercise and your food can getting a more control BG range while staying in sleep activity more effective. Also for those who feel that have more unpredictable blood sugar, staying in sleep activity can cause you to have much less of a buffer if your blood sugar decides to nose-dive on you.

Can I bolus in sleep activity?

Why yes you can. Which is awesome. You just can’t exercise in sleep activity, and vice versa, but you’d expect that since these are 2 entirely different activities.

Lastly and MOST Importantly…

You are still responsible for managing your diabetes but it needs your active participation such as meals and activities also remember change out your pump and site as needed and ALWAYS pay attention to your symptoms. Hopefully this information as helpful to you! For more information, you can always check out my YouTube Channel and follow me on Instagram.

For More Help with Your Diabetes If you need help with your diabetes management, we can work together through my online Telehealth Private Practice. As a T1D, who is also a diabetes educator and a Registered Dietitian, I understand what you are going through and I know how to help you. Together we will troubleshoot your biggest obstacles, figure out what is causing unpredictable blood sugar drops and rises, and reduce insulin resistance for better health and weight loss. I care about you and I’m here to help. Either visit me on my website or message me so we can start talking.


Ariel Warren, RDN, CD, CDCES

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