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Loop and open-source diabetes tech

Some families don't wait for a company to connect their pump and CGM. They build the connection themselves, with free software written by other people living with Type 1. Here's what that means, and what to weigh before you try it.

In short

Loop and its cousins let a phone run your pump from your CGM, automatically. Thousands of families use them. They're free, but you build and run them yourself, so start the conversation with your care team first.

What “looping” means

An automated insulin delivery system (often called a closed loop or an artificial pancreas) has three parts. A CGM measures glucose every few minutes. An algorithm predicts where glucose is heading. A pump adjusts insulin to match. You still tell it about meals, but it handles a lot of the small corrections in between, including overnight.

  1. 1

    The CGM

    Sends a reading every 5 minutes.

  2. 2

    The algorithm

    Runs on a phone, predicts the next few hours, and decides on a dose.

  3. 3

    The pump

    Delivers the adjusted insulin, then the cycle repeats.

Commercial systems such as Tandem Control-IQ, Omnipod 5 and the MiniMed 780G do this with software the manufacturer wrote and the FDA cleared. Open-source systems do the same job with software written and shared by the diabetes community. You install it yourself.

#WeAreNotWaiting: where it came from

Around 2013, parents and adults with Type 1 got tired of waiting for devices to talk to each other. A father wanted to see his son's CGM readings from work, so he wrote code to send them to the cloud. That became Nightscout, and the rallying cry became #WeAreNotWaiting.

Once the data could leave the CGM, the next step was to act on it. OpenAPS published the first open-source closed-loop design in 2015. Loop followed for the iPhone, and AndroidAPS for Android. All of it is free, published openly, and maintained by volunteers, many of them parents. The movement also pushed the industry: Tidepool took Loop through the FDA, and Tidepool Loop was cleared in 2023.

A closer look at Loop

Loop is an iPhone app. It reads the CGM, predicts glucose a few hours ahead from your insulin, carbs and settings, and adjusts the pump's basal rate (and, if you turn it on, gives small automatic boluses) to bring glucose toward your target.

Phone
An iPhone, which needs to stay near the pump and CGM. For a child, that usually means the child carries it.
CGM
Dexcom sensors work directly. Some other sensors work with extra setup; check LoopDocs for the current list.
Pump
Omnipod DASH works over Bluetooth, and so do some Dana pumps sold outside the US. Older Omnipod (Eros) and some older Medtronic pumps also work, with a small radio bridge such as a RileyLink. Most current US tubed pumps are not supported.
Building it
You build the app yourself, either on a Mac with Apple's Xcode or from a web browser using GitHub. Either way you need an Apple developer account (about $99 a year) and you rebuild it at least once a year.
Following along
Parents can watch glucose, insulin and carbs remotely through Nightscout or apps such as LoopFollow, and can send remote carbs or boluses if they set that up.
Help
LoopDocs, the step-by-step documentation, is the place to start. The “Looped” groups on Facebook have thousands of parents who have built it for their kids.

The other open-source systems

Trio
An iPhone app, like Loop, that uses the OpenAPS algorithm. Families who want more automatic correction options often compare Trio and Loop.
AndroidAPS
The Android option, also built on the OpenAPS algorithm. It supports a wider range of pumps than the iPhone apps, which matters outside the US.
OpenAPS
The original open-source closed loop, run on a tiny computer. Its algorithm lives on inside Trio and AndroidAPS.
Nightscout
Not a loop, but the remote-monitoring site that started it all. Many families use it with commercial systems too, to see their child's numbers from anywhere.
Tidepool Loop
Loop's algorithm, taken through FDA clearance by the nonprofit Tidepool. It's used in commercial devices rather than as a do-it-yourself build.

What the research says

Open-source looping isn't just anecdote. Two studies are the most cited:

  • The CREATE trial (New England Journal of Medicine, 2022)

    A randomized trial in New Zealand of 97 children and adults. People using an open-source system (built on AndroidAPS) spent about 14 percentage points more time in range, roughly 3 hours a day, than people using a pump and CGM without automation. The benefit held for children and adults, with no severe lows or DKA in either group. Read the study

  • The Loop observational study (2021)

    A six-month real-world study of 558 Loop users aged 1 to 71, most of whom set it up with community resources. Time in range rose from 67% to 73% on average, and severe lows were far less common than in the months before they started. Read the study

Weighing it up

Why families choose it

  • Works with pumps you may already have, like Omnipod DASH.
  • Free software, and settings you can adjust in detail.
  • Strong remote following and remote control for parents.
  • A large, generous community of other parents.

What to be ready for

  • It isn't FDA-approved as you build it. You're responsible for running it.
  • Setup takes an evening or two, and it needs rebuilding each year.
  • Settings matter a lot. Wrong settings can mean wrong doses.
  • Not every clinic will support it, and manufacturers won't help with it.

This is not a first-week project. Get comfortable with the basics, your pump and your CGM first. Before you loop, talk to your diabetes care team about your settings, keep a backup plan for injections, and keep checking with a meter when symptoms don't match the numbers.

Questions to bring to your care team

  1. 1Do you have other patients using Loop, Trio or AndroidAPS?
  2. 2Would you review our basal rates, carb ratios and correction factors before we start?
  3. 3Would an FDA-cleared system, like Omnipod 5 or Control-IQ, suit us just as well?
  4. 4What should we do, and who should we call, if the loop stops working?
  5. 5How should school or daycare handle it?