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Thinking of Starting Loop?

What is Loop?

Loop is an app you build yourself and load on your iPhone (or iPod) that uses a compatible continuous glucose monitor (CGM) and is paired using a “radio-link” with your compatible pump. Loop assists in the many dosing decisions people with diabetes face every day. Loop works with older Medtronic pumps and the Eros Omnipods. There is a version of Loop under development that adds support for Omnipod DASH; with DASH, Loop does not need the “radio-link”.  For the CGM, the Loop app works with Dexcom’s Continuous Glucose Monitor (CGM) or the Medtronic Sensor, but there are other versions of Loop available that may work for you if you are not using one of these specific CGMs.  Check out the compatible CGM section later.

What Should I Expect from this Starting Loop Series?

Many people find it easier to learn about and start to Loop by breaking the information into smaller bite-sized pieces. This document was originally written as a variation of an Advent Calendar posted several years ago on the FaceBook Looped group. That calendar was very helpful to many people. The concept of taking this process one step at a time was captured in the Build Section in the Loopdocs webpage. That documentation is incredibly detailed and may appear overwhelming at first glance. You may find it helpful to review both sites in deciding about your Loop journey.

Loop is a Do-It-Yourself (DIY) project but not a Do-It-Alone project.  There is a wonderful community of mentors happy to help.

We hope you find these articles informative and helpful as you begin your Loop journey.

What is a Radio-Link?

Loop requires a RileyLink compatible device (that’s a mouth full, so we use radio-link for short) to allow the pump and phone to talk to each other. This small additional device must be kept in range of your pump and phone for closed-loop control.  The images below show that device, a radio-link called a “RileyLink,” that communicates between the phone (which speaks in Bluetooth) and the pump (which speaks in radio frequency).   Over the last few years, several designers have developed alternate versions of these links.  So, in most cases, we’ve updated our terminology on this site to refer to these devices generically as a “radio-link,” but most graphics show a RileyLink.  On other sites or on Facebook, you may see references to RileyLink Compatible Devices rather than radio-link, but both terms are referring to the exact same devices.  (The RileyLink was named after the daughter of the person who designed it. Other radio-link devices currently available for purchase include the EmaLink and OrangeLink.)


Is Loop for Me?

Loop requires a substantial commitment to learning and understanding the technology, processes, algorithms, and troubleshooting flows.

Loop is NOT for everyone. But everyone who wants to Loop can find help from many volunteers in the Looping community.

Read this introduction, decide if you want to continue, and, if you do, welcome aboard.

What You do NOT Need to Loop:

  • You do not need to be a computer scientist to build and run Loop
  • You do not even need to understand how to set the time on your VCR

What you DO Need to Build and Use Loop:

  • You need to be able to read and follow instructions
  • You need to make a commitment to carefully test your settings and adjust them
  • You need to make a commitment to coming back to the support forums on a regular basis to see if there are any important safety updates
  • You need to know how to troubleshoot and where to find the most current troubleshooting information
  • You need to know how to turn-off auto-updating on your phone iOS

You may notice there is a lot of “You” in the above. That is because you should not Loop unless you commit to staying up-to-date on Loop. Best practice: at least once a week, you should be going to your favorite support forum and reading the posts, visiting the Loop and Learn Home Page and reading the Announcements, or signing up for the Newsletter.

If, after reading the documentation here, you decide building Do-It-Yourself Loop is not for you, THAT’S OKAY!

There are other options available now. Medtronic was first to market with a hybrid closed loop using their pumps and sensors. Control-IQ and Basal-IQ are available for the T-Slim pumps from Tandem Diabetes for users of the Dexcom G6 CGM. Insulet has their version of hybrid closed loop with the Omnipod 5. (Note: there are DIY choices that use Eros or DASH pods; the Omnipod 5 pods are different and there are no DIY solutions that use those pods.)

If you are weighing the pros and cons of Loop compared to a commercial system, I recommend reading this SeeMyCGM blog post from someone who moved their child from Loop to a Tandem product before going any further. For people who do not want to invest in the Apple ecosystem, there is also an Android option. The Android and commercial options are outside the scope of this Starting Loop series.

There is a Choosing Your DIY article on this website that discusses and provides links to Android APS as well as another iPhone option.


You are completely responsible for your own technology and settings decisions.

  • Do not pay someone to build Loop for you
  • Do not have it installed for you at a “Build Party”

You need to have all the bits and pieces available to rebuild it, if necessary, and you need to understand how to do that build with limited hand holding.

Loop is experimental. Loop is not approved for therapy by any official government agency. In some countries, you can get yourself into serious legal trouble for helping someone Loop.

Loop is only as good as your CGM.  If your sensor is noisy or you do not trust the readings for any reason – please OPEN your Loop.  You can still use your phone to control your pump manually, but Loop will not automatically give insulin (other than scheduled basal) without your explicit command.

You take full responsibility for building and running this system and you do so at your own risk!

Your Settings are Critical for Successful Use of Loop

If you are not comfortable figuring out your own basal rates, carb ratios, insulin sensitivity, and refining those on a somewhat regular basis, then Loop is not for you – yet.  But once again, if you’re willing to do the work, there are lots of mentors available to help you.

You can count on your fingers the number of doctors in the US who are capable of properly adjusting settings for Loop.  You can probably count on your fingers and toes the number worldwide who can successfully help you with Loop settings.   If you are not familiar with books such as “Using Insulin,” “Pumping Insulin,” “Think Like a Pancreas,” “Sugar Surfing,” or other similar methods of figuring out and adjusting your own settings, you will need to do some reading, learning, and testing before you can be successful with Loop.  LoopTips has Settings Overview and Adjustment sections well worth your time.  Note that LoopTips was written several years ago and many features of Loop have been upgraded since then. 

There are people who have tried to Loop and have decided it was not for them (that’s OKAY).  The most common reasons that people will fail in their Loop attempts are:

  • Not understanding the algorithm-based control system (more explanations later)
  • Getting confused by settings and not understanding their interactions
  • Not realizing that insulin has a very long tail (duration of action); Loop uses this in its predictions
  • Failure to stay informed about Announcements in the Looped community
  • Having someone else build Loop without understanding it themselves

It is a mistake to find someone to build Loop for you.  You need to take the time and expend the brainpower to understand the fundamental concepts of what is being built.

History and background

If you’re interested in the history and some technical details about Loop, here are a few interesting articles:

There are several different flavors of DIY artificial pancreas systems (APS) and one of the founders of OpenAPS recently published this book:

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