Loop (iOS)

Loop is an open-source automated insulin delivery (AID) app that runs on the iPhone, built and maintained by the volunteer LoopKit community.¹ Unlike commercial AID, the app is not on the App Store — you compile it yourself from source onto your own device, which is the central fact of using it.¹

Platform and algorithm. Loop is iOS-only (it also runs on Apple Watch); there is no Android version — the equivalent Android project is the separate AndroidAPS.² Its algorithm is a model-predictive control (MPC) design that, every five minutes when a new sensor value arrives, forecasts glucose out to the insulin action duration using insulin-on-board, entered carbohydrates and a dynamic carbohydrate-absorption model that revises how fast a meal is actually being absorbed from the observed glucose response.³ This lineage is distinct from the OpenAPS/oref family that powers AndroidAPS and Trio.⁴ Loop 3 can dose by automatic micro-bolus (delivering a fraction of the recommended correction each cycle) rather than temp-basal only.³ Notably, Loop deliberately does not auto-adjust your insulin sensitivity the way OpenAPS "autosens" does — it trusts the therapy settings you give it, applying only a short-term retrospective correction for the last hour; meals work best when announced, though it is "fairly forgiving" of unannounced ones.³ That design choice favors predictability over maximal automation.

Supported hardware. Loop drives Omnipod DASH (Bluetooth, no radio bridge) and the older Omnipod Eros, several older Medtronic pumps, and Dana and Medtrum patch pumps; Omnipod 5 is not yet supported.² For glucose it reads Dexcom G6/G7/ONE, European Libre 2 and Libre 1 (via transmitter), and Eversense — but not Libre 3 or the US Libre 2 directly.² Eros and Medtronic pumps need a RileyLink-class radio bridge; the newer Bluetooth pumps do not.²

Community and support. Loop has unusually deep documentation (LoopDocs) and a large volunteer support network — Loop and Learn, Facebook and Discord groups, and live sessions offer build help.⁵¹ More than 9,000 people were estimated to be using Loop by the time of a 2022 Stanford study.⁵

Legal and self-responsibility status. DIY Loop is not a regulated medical device; you build and run it at your own responsibility, and LoopDocs is explicit that you must know how to set up, operate and troubleshoot it.¹ Importantly, the Loop algorithm became the basis for Tidepool Loop, which the FDA cleared in January 2023 as the first interoperable automated glycemic controller (iAGC) supported by real-world evidence rather than a classical trial — the first regulatory clearance of an open-source AID algorithm.⁴⁶

Clinical evidence. In a prospective real-world study of 558 adults and children, Loop raised time-in-range from 67% to 73% and lowered HbA1c from 6.8% to 6.5% over six months, with no increase in severe hypoglycemia.⁷ Qualitative work with Loop users reports reduced management burden and better quality of life, alongside real setup and troubleshooting friction.⁵ (The randomized CREATE trial of open-source AID used the OpenAPS algorithm in AndroidAPS, not Loop, so it speaks to the open-source approach generally rather than to Loop specifically.⁴)

What's coming. Active development continues under LoopKit: Omnipod 5 pod support is in private beta, and Dana pump support is maturing on feature branches.² The bigger arc is convergence with the regulated world — Tidepool Loop's clearance opens a path for the DIY-born algorithm to reach people who can't or won't self-compile, while the open project keeps iterating on dosing strategies and hardware reach.⁶⁴

References

1. LoopKit community. LoopDocs — Loop FAQs (the app is not downloadable; you build it yourself and operate it at your own responsibility). Accessed 2026. https://loopkit.github.io/loopdocs/faqs/loop-faqs/ ↩ ↩² ↩³ ↩⁴

2. LoopKit community. LoopDocs — Compatible Pump and Compatible CGM (Omnipod DASH/Eros, Medtronic, Dana, Medtrum; Dexcom, Libre 2, Eversense; RileyLink requirements; Omnipod 5 in beta). Accessed 2026. https://loopkit.github.io/loopdocs/build/pump/ ↩ ↩² ↩³ ↩⁴ ↩⁵

3. LoopKit community. LoopDocs — Algorithm overview, Dynamic Carbs, Bolus recommendations & Algorithm FAQs (model-predictive control; dynamic carb absorption; automatic bolus; no autosens-style sensitivity learning). Accessed 2026. https://loopkit.github.io/loopdocs/operation/algorithm/overview/ ↩ ↩² ↩³

4. Braune K, Hussain S, Lal R. The First Regulatory Clearance of an Open-Source Automated Insulin Delivery Algorithm. Journal of Diabetes Science and Technology (2023); 17(5):1139–1141. According to PubMed. https://pmc.ncbi.nlm.nih.gov/articles/PMC10563523/ (DOI) ↩ ↩² ↩³ ↩⁴

5. Suttiratana SC, Wong JJ, Lanning MS, et al. Qualitative Study of User Experiences with Loop, an Open-Source Automated Insulin Delivery System. Diabetes Technology & Therapeutics (2022); 24(6):416–423. According to PubMed. https://pmc.ncbi.nlm.nih.gov/articles/PMC9208860/ (DOI) ↩ ↩² ↩³

6. Tidepool. Tidepool Loop has received FDA Clearance! (January 2023; first FDA-cleared interoperable automated glycemic controller built on the open-source Loop algorithm). https://www.tidepool.org/blog/tidepool-loop-has-received-fda-clearance ↩ ↩²

7. Lum JW, Bailey RJ, Barnes-Lomen V, et al. A Real-World Prospective Study of the Safety and Effectiveness of the Loop Open Source Automated Insulin Delivery System. Diabetes Technology & Therapeutics (2021); 23(5):367–375. According to PubMed. https://pmc.ncbi.nlm.nih.gov/articles/PMC8080906/ (DOI) ↩