Tandem t:slim X2 (pump)

The Tandem t:slim X2 is a slim, rechargeable, touchscreen insulin pump — a tubed pump, meaning the reservoir sits in the device on your belt or pocket and thin tubing carries insulin to an infusion set on the skin (unlike a tubeless "patch" pump worn directly on the body).¹ Its defining trait is that it improves by software: it was the first pump the FDA authorized as an "alternate controller enabled" (ACE) interoperable pump, designed to mix and match with compatible CGMs and automated-dosing algorithms.² In practice that has meant new features arriving as free over-the-air updates through the Tandem Device Updater, rather than as new hardware.¹

Reservoir and wear. The cartridge holds up to 300 units of insulin — larger than most patch-pump reservoirs.¹ The cartridge and its infusion set are typically changed about every 2–3 days; the pump body itself is reusable, runs on a built-in rechargeable battery charged by USB, and is watertight to an IPX7 rating (tested to ~3 feet / 30 minutes, not a swimming device).³ It weighs about 112 g with a full cartridge.³

Infusion set and occlusion detection. It works with a range of infusion sets (different cannula materials, tubing lengths and insertion angles).¹ Like other modern pumps it monitors delivery and raises occlusion / "no-delivery" alarms if it detects a blockage; in the pivotal six-month trial the only serious device-related event was a single episode of diabetic ketoacidosis, with no severe hypoglycemia.⁴

CGMs, algorithms and DIY. The pump runs Tandem's Control-IQ+ algorithm, an advanced hybrid closed-loop system that automatically raises, lowers and suspends basal insulin and can deliver automatic correction boluses when high glucose is predicted.⁵ It integrates with the Dexcom G6 and G7 sensors and, via later software updates, Abbott's FreeStyle Libre 2 Plus and the 15-day FreeStyle Libre 3 Plus.⁶⁷ It is a closed commercial system — it is not open to community/DIY loops the way some older pumps are. In the foundational DCLP3 randomized trial, Control-IQ raised time-in-range from 61% to 71% versus an unchanged 59% on a sensor-augmented pump, with the system in closed-loop mode ~90% of the time.⁴ Benefits held in adolescents and young adults⁸ and in a one-year real-world pediatric cohort (time-in-range 51.6% → 64.4%),⁹ and a large post-approval dataset showed a 73.6% median time-in-range across 9,451 users.⁷

Phone bolusing. On supported iOS/Android phones the Tandem t:slim mobile app lets you bolus and dose from the phone, not just the pump touchscreen.¹

Access and cost. It is cleared and sold across the US, UK, EU, Canada and Australia, generally through durable-medical-equipment or pharmacy channels; insurance/health-system coverage varies and uncovered cost is substantial.¹

What's coming. The platform is actively expanding: in 2025 the FDA cleared Control-IQ+ for adults with type 2 diabetes (previously type 1 only), and the FreeStyle Libre 3 Plus integration rolled out as a free update to existing pumps.⁵⁶ Tandem is also positioning its smaller Tandem Mobi pump alongside the t:slim X2 on the same Control-IQ+ automation, pointing toward a future where the algorithm — not the box — is the product.⁷

References

1. Tandem Diabetes Care. t:slim X2 Insulin Pump (product page — 300-unit cartridge, rechargeable battery/USB, Tandem Device Updater software updates, Control-IQ+, Dexcom G6/G7 and FreeStyle Libre 3 Plus compatibility, t:slim mobile app bolus). https://www.tandemdiabetes.com/products/insulin-pumps/tslim-x2-insulin-pump ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

2. U.S. Food and Drug Administration. FDA authorizes first interoperable insulin pump intended to allow patients to customize treatment through their individual diabetes management devices (Tandem t:slim X2 as first "alternate controller enabled" ACE pump). FDA News Release, February 14, 2019. https://www.fda.gov/news-events/press-announcements/fda-authorizes-first-interoperable-insulin-pump-intended-allow-patients-customize-treatment-through ↩

3. Tandem t:slim X2 technical specifications (IPX7 watertight rating, ~3 ft/30 min; ~112 g with full 300-unit cartridge; rechargeable battery). MedicalNewsToday device overview (2025). https://www.medicalnewstoday.com/articles/t-slim-pump ↩ ↩²

4. Brown SA, Kovatchev BP, Raghinaru D, et al. Six-Month Randomized, Multicenter Trial of Closed-Loop Control in Type 1 Diabetes (DCLP3 / iDCL). New England Journal of Medicine 381(18):1707–1717 (2019). PMID 31618560. https://doi.org/10.1056/NEJMoa1907863 ↩ ↩²

5. U.S. Food and Drug Administration. FDA Roundup: February 28, 2025 — FDA cleared Tandem's Control-IQ+ technology, an interoperable automated glycemic controller (iAGC) that adjusts basal insulin and delivers correction boluses, for type 2 diabetes. https://www.fda.gov/news-events/press-announcements/fda-roundup-february-28-2025 ↩ ↩²

6. U.S. Food and Drug Administration. FDA Clears First Device to Enable Automated Insulin Dosing for Individuals with Type 2 Diabetes (Control-IQ+ as iAGC; works with iCGM + ACE pumps). FDA News Release, 2025. https://www.fda.gov/news-events/press-announcements/fda-clears-first-device-enable-automated-insulin-dosing-individuals-type-2-diabetes ↩ ↩²

7. Review of the t:slim X2 and Mobi insulin pumps with Control-IQ: patient safety and device efficacy (CGM compatibility incl. Dexcom G6/G7 and Libre 2 Plus; pivotal 71% vs 59% time-in-range; post-approval 73.6% median time-in-range across 9,451 users; Mobi shares the platform). PMC (2025). https://pmc.ncbi.nlm.nih.gov/articles/PMC13089864/ ↩ ↩² ↩³

8. Isganaitis E, Raghinaru D, Ambler-Osborn L, et al. Closed-Loop Insulin Therapy Improves Glycemic Control in Adolescents and Young Adults: Outcomes from the International Diabetes Closed-Loop Trial. Diabetes Technology & Therapeutics 23(5):342–349 (2021). PMID 33216667. https://doi.org/10.1089/dia.2020.0572 ↩

9. De Meulemeester J, Valgaerts L, Massa G, et al. Real-World Glycemic and Person-Reported Outcomes After Tandem Control-IQ Initiation in Children With Type 1 Diabetes (1-year cohort; time-in-range 51.6%→64.4%). Journal of Clinical Endocrinology & Metabolism 110(12):3331–3341 (2025). PMID 40333328. https://doi.org/10.1210/clinem/dgaf265 ↩