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Survive & Thrive · AID Series

Tandem t:slim X2 + Control-IQ : what it offers, how to get the most from it

Side 1 of 2
What Control-IQ offers
t:slim X2 · Control-IQ
System profile

Tandem Control-IQ at a glance

CF
Primary optimisation lever Correction Factor (CF). Strongest CF quartile achieves 14% more TIR than the weakest (Messer 2023, 20,764 users).
Best-quartile TIR
79.1%
strongest CF cohort
Registry
20,764
Messer et al. 2023
Age
6+
years and older
Ref: Breton MD et al. 2020 NEJM (pivotal) · Messer LH 2023 · Shah VN 2026 DOM · Pemberton & Uday 2026 (configuration).
The essentials
✓Tubed pump. 3-day infusion set, 300U reservoir.
✓Control-IQ algorithm runs on the pump. Adjusts basal every 5 min.
✓Compatible CGMs: Dexcom G6 / G7. Not Libre.
✓Fixed target 6.1 mmol/L. Cannot be lowered. Optimisation is via CF and Sleep Mode.
✓Sleep Mode - tighter overnight target. Can be activated 24/7 for stronger algorithm control.
✓Exercise Mode - raises target to 7.8-8.9 mmol/L, reduces basal.
✓Most customisable AID. Your settings (CF, ICR, basal) shape the algorithm.
GNL 5-level framework · Pemberton & Uday 2026, updated 17 Apr 2026 with Laurel Messer

Five levels, three ranked primary levers

Level1. CF rule2. Basal % (calc)3. ICR rule
5 Optimal80 / TDD65%300 / TDD
4 High85 / TDD60%330 / TDD
3 Balanced (start here)90 / TDD55%400 / TDD
2 Gentle100 / TDD50%450 / TDD
1 Protective110 / TDD45%500 / TDD
CF is the primary lever on Control-IQ. Strengthens both the 5-min delivery and the Autobolus. Messer 2023 (n=20,764): strongest CF quartile achieves 14% more TIR than the weakest. Basal % is a calculation for setting programmed basal rates (not a target). ICR is the user-delivered bolus lever.
Start at Level 3 for most adults. Step up to 4 and 5 as fast as you tolerate. Stop condition: time below range (< 3.9 mmol/L) above 4%. Children often need a stronger ICR from the start per ISPAD 2024 (330 or 250 / TDD for preschoolers). Pre-load profiles for Levels 2, 3, 4 and 5.
Sleep Activity · additional consideration, not a level

Two modes, depending on meal bolusing

  • Run 24/7 when you give most of your boluses for meals. 5-min delivery tightens, Autobolus disabled (not needed).
  • Run at night only when daytime meal boluses are regularly missed. Keeps the daytime Autobolus active to cover meal excursions.
  • Do not run 24/7 if boluses are missed. Removing the daytime Autobolus typically leads to more hyperglycaemia, not hypo.
  • Sleep Activity tightens target to 6.25-6.7 mmol/L with stronger 5-min delivery; Autobolus disabled while active.
Exercise Mode

Managing exercise on Control-IQ

  • Activate 60-90 min pre-exercise. Raises target range, reduces basal and disables auto-correction.
  • Stays on until you turn off. Keep it on during the session and 60 min after.
  • Long sessions - combine with reduced mealtime bolus. Exercise Mode alone won't cover 90 min running.
  • Don't forget to turn it off. Leaving it on overnight will drive your glucose high.
Auto-corrections

What Control-IQ does on its own

  • Basal adjustment every 5 min based on predicted glucose 30 min ahead.
  • Autobolus delivered if predicted > 10 mmol/L and basal adjustment alone is insufficient. 60% of the calculated correction. Up to once per hour. Delivered without user confirmation - the pump sends it directly and logs it in history.
  • Disabled by Sleep Activity. Autobolus turns off while Sleep Activity is on (overnight if nightly; all day if 24/7 Sleep).
  • Not replacing meal bolus. Your pre-meal bolus still does most of the work.
Survive & Thrive · AID Series

Tandem t:slim X2 + Control-IQ : the 20% that makes 80% of the difference

Side 2 of 2
How to get the most out of it
t:slim X2 · Control-IQ
Major in the majors · #1

Three settings that move almost everything

  • Correction Factor (CF). Start at 80-90 / TDD based on your team's guidance. Review every 4 weeks.
  • Insulin-to-Carb Ratio (ICR). Meal boluses live here. Get this right before optimising the algorithm.
  • Basal rates. Hourly profile - Control-IQ adjusts around this. Foundation must be close to correct.
  • Sleep Activity. Additional consideration, not a level. Run 24/7 if bolusing regularly for meals; run at night only if daytime boluses missed. Never 24/7 without regular meal bolusing (leads to hyperglycaemia, not hypo).
Major in the majors · #2

Infusion sets and sites

  • Change every 3 days maximum. Longer wear = more absorption variability = algorithm struggles.
  • Site rotation. Abdomen, lower back, thighs, upper outer arm. Don't reuse a site for 2 weeks.
  • Prime properly. Forgetting to prime the cannula after insertion is a common cause of unexplained highs.
  • Consider steel sets if teflon kinks. Less comfortable, more reliable in some people.
  • Change in the morning - you'll spot absorption issues before bedtime.
Major in the majors · #3

Two actions that move HbA1c most

The AID Optimiser models what CF and Sleep Mode changes will do. Use it before you change anything.

Action 1 AID Algorithm OptimiserModel CF and Sleep Mode changes for Tandem Control-IQ. See expected TIR shift before you commit. → Action 2 Exercise Planning ExplorerExercise Mode timing and bolus reductions for your session type. →
Go deeper

GNL explorers, guides & podcasts

Interactive tools, graded evidence and long-form reading when you want more than a leaflet.

GuideFull AID Guide - 5-part seriesHow every AID algorithm works, side by side.→ SystemGNL Tandem Control-IQ PageDeep dive - TypeZero algorithm, registry data, Sleep Mode strategy.→ PodcastAID Series - Control-IQ episodesTandem user experience, clinician perspective, optimisation discussion.→ AskGrace - evidence-backed Q&AAsk anything about Control-IQ, AID or T1D.→