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

Pregnancy, and type 2 diabetes. On 27 April 2026 the FDA cleared Control-IQ+ — the algorithm this pump runs — for use in pregnancy complicated by type 1 diabetes, making it the first and only automated insulin delivery system cleared for pregnancy in the US (on both the t:slim X2 and the Tandem Mobi).¹⁰ That is a US-first, not a world-first: in Europe the CamAPS FX algorithm, which runs on other pumps, has been licensed in pregnancy for years. The clearance rests on the CIRCUIT randomized trial, published in JAMA in 2025: among 91 pregnant women with type 1 diabetes in Canada and Australia, those using Control-IQ spent 65.4% of the time from 16 to 34 weeks' gestation in the tighter pregnancy target range of 63–140 mg/dL (3.5–7.8 mmol/L), versus 50.3% on standard care — a mean adjusted difference of 12.5 percentage points (95% CI 9.5–15.6), or roughly three extra hours a day.¹¹¹² It was a small, open-label trial whose primary outcome was glucose time-in-range, not the pregnancy complications that time-in-range stands in for; on safety, there was one episode of severe hypoglycemia in the closed-loop group, and two episodes of diabetic ketoacidosis in the closed-loop group against one on standard care.¹¹ That is a pregnancy-specific range, so it is not comparable with the 70–180 mg/dL (3.9–10.0 mmol/L) time-in-range figures quoted above, and it does not change this pump's scores. Then on 5 June 2026 Tandem announced a CE mark expansion in Europe covering the same pregnancy indication plus adults with type 2 diabetes, again for both the t:slim X2 and the Mobi.¹² Both are regulatory expansions of who may be prescribed the system rather than new evidence in type 1 outside pregnancy; the European type 2 indication rests on a separate trial in type 2 diabetes and says nothing about type 1 outcomes. The algorithm itself is covered in more depth on our Control-IQ+ entry.

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 The 2026 label expansions widen who can be prescribed it — pregnancy with type 1 diabetes in the US and Europe, and adults with type 2 diabetes in Europe — but they do not change what it costs.¹⁰¹²

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 That expansion continued through 2026 with the US pregnancy clearance (April) and the European CE mark for pregnancy and type 2 diabetes (June).¹⁰¹² 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 ↩

10. Tandem Diabetes Care. Tandem Diabetes Care's Control-IQ+ Automated Insulin Delivery Technology Now FDA Cleared for Pregnancy in Type 1 Diabetes (clearance 27 April 2026; first and only AID system cleared for pregnancy in the US; covers t:slim X2 and Tandem Mobi). Business Wire, 27 April 2026. https://www.businesswire.com/news/home/20260427815489/en/ ↩ ↩² ↩³

11. Donovan LE, Lemieux P, Dunlop AD, et al. Closed-Loop Insulin Delivery in Type 1 Diabetes in Pregnancy: The CIRCUIT Randomized Clinical Trial (open-label, 14 centres in Canada and Australia; 91 randomized; primary outcome time in the pregnancy-specific range 63–140 mg/dL from 16–34 weeks' gestation: 65.4% closed-loop vs 50.3% standard care, mean adjusted difference 12.5 percentage points, 95% CI 9.5–15.6; ClinicalTrials.gov NCT04902378). JAMA 334(24):2176–2185 (2025). PMID 41134589. https://doi.org/10.1001/jama.2025.19578 ↩ ↩²

12. Tandem Diabetes Care. Tandem Diabetes Care Automated Insulin Delivery Systems Receive CE Mark for Type 2 Diabetes and Type 1 Diabetes During Pregnancy (CE mark granted 5 June 2026; pregnancy indication based on the CIRCUIT randomized trial, whose primary publication is cited above; type 2 indication based on the separate 2IQP trial). Business Wire, 5 June 2026. https://www.businesswire.com/news/home/20260605572579/en/ ↩ ↩² ↩³ ↩⁴