Thinking about the Tandem t:slim X2 with Control-IQ — the Spider-Man of AID systems?
“With great power comes great responsibility.”
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Episode 2: Mastering Control-IQ – The Spider-Man of AID focuses on the Tandem t:slim X2 with Control-IQ, a highly customisable system offering flexibility and control. It covers how the algorithm works, key settings, and practical strategies to help you get the most out of it.
Things to look forward to:
- Highly customisable algorithm with potential for multiple insulin profiles
- Activity and Sleep modes to stay in target
- A high degree of flexibility
Here are the t:slim X2 with Control-IQ essentials:
- How the algorithm works
- Starting settings
- Tips and tricks
- Preventing and treating hypos
- High-fat meals
- Exercise
How the algorithm works
The t:slim X2 system has three components:
- The t:slim X2 pump
- Dexcom G6, Dexcom G7, or Libre 2 Plus (region dependent)
- The Control-IQ algorithm inside the pump
This graphic explains how Control-IQ works in a nutshell.
Take-homes
- The algorithm uses manually set basal rates and correction factors — giving flexibility and responsibility.
- Basal increases when glucose is rising but below 10.0 mmol/L (180 mg/dL).
- Auto-correction bolus if glucose is predicted above 10.0 mmol/L — 60% of the required correction per hour.
- Basal decreases or suspends if glucose is predicted to go low.
- Control-IQ targets 6.3–8.9 mmol/L (113–160 mg/dL).
Starting settings
The Control-IQ algorithm calculates adjustments from manually set basal rates and correction factors. Your diabetes team can help ensure these are close to what you need. Direct them to the AID Study Day, which includes a calculator for optimal starting settings.
Research shows the Correction Factor is the key setting to adjust to change algorithm aggressiveness without causing hypos.
Achieve at least 70% time in range before creating a second profile. Only add profiles if your sensitivity differs on certain days. As Francesca Annan says: “Find out before you fiddle.”
Starting an AID system happens in two phases:
SURVIVE
THRIVE
Download the How to Survive and Thrive Guide — t:slim X2. A full workbook is also available: t:slim X2 Workbook.
Tips and tricks
If you want 70%+ TIR, do not forget the basics:
- Three balanced meals
- Accurate carbohydrate counting
- Bolus insulin 10–20 minutes before eating
- Be active for 10–15 minutes after eating
- Rotate cannula sites
99 Problems But Highs Ain’t One — download/share
Other things to be aware of:
- Always suspend the pump when disconnecting (showers, sport, sex).
- Set Sleep mode to usual sleep times — the system targets waking at 6.1 mmol/L (110 mg/dL).
- Adjust the Correction Factor to optimise performance.
- Update insulin settings when sensitivity changes:
- Weight loss
- New exercise regime
- Children/young people: every clinic visit (~3 months)
Preventing and treating hypos
Hypos will still happen with bolus errors or exercise without planning.
The algorithm often reduces insulin early, so you usually need less hypo treatment than before.
This chart illustrates treatment for a 30 kg person. Use the Survive and Thrive Guide to create your own personalised version.
Download the hypo guide here.
High-fat meals
High-fat, high-carb meals (pizza, takeaways) require additional insulin. Control-IQ’s fixed 5-hour active insulin time makes it slow to respond.
Solution: increase carbs entered by 25–50% and use an extended bolus (50% now, 50% over 2 hours).
Example: For a 100 g carbohydrate pizza, enter 125 g and set a 50/50 split. If still high, use 150 g (50% extra) next time.
Trial and error is required.
Exercise
Two approaches: quick method and comprehensive method.
The quick method
Turn on Activity mode 90 minutes before exercise and take small carbohydrate top-ups every 20 minutes.
Avoid large carb loads — they trigger extra insulin and increase hypo risk.
Pro tip: Give a 0.1 unit manual bolus before starting exercise. This blocks auto-corrections for 60 minutes.
Carbohydrate needs depend on weight. Here is an example for a 50 kg person:
Download the exercise charts: mmol/L | mg/dL.
The comprehensive method
Work through the Exercise Guide to understand exercise types, bolus reductions, and adapting plans.
Once ready, the T25/T25 table will make sense. See also the AID and Exercise Consensus Guideline.
This downloadable exercise tool simplifies planning.
Go forth and conquer Control-IQ.
Check out the top ten tips to optimise time in range podcast.
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