So You Want to Start Looping?

Loop is an app you build on your iPhone (or iPod) that is paired with your compatible pump and compatible CGM to assist in the many dosing decisions people with diabetes face every day. Many people find it easier to learn about and start to Loop by breaking the information into smaller bite-sized pieces. This document is a variation of the Advent Calendar from a year or so ago on the main FaceBook Looped group. That calendar was very helpful to many people. The concept of taking it a step at a time was captured in the Build Step# structure in Loopdocs. That documentation is incredibly detailed.

This is an attempt to revive the Advent Calendar concept with current information maintained and updated by multiple people in the Looping community. Loopdocs remains the main repository of information on how to build Loop.


If you find yourself on this page because someone sent it to you, you should probably stop for a minute and ask yourself, “Do I understand what I am getting myself into?”

Loop is NOT for everyone. Loop requires a substantial commitment to learning and understanding the technology, processes/algorithms, and troubleshooting flows. 



  • 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.


  • You do need to be able to read and follow instructions.
  • 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. Some recent issues that caught people by surprise were a change in how Apple handles Profiles and Certificates which made Loop quit working unexpectedly, and the Time Zone change bugs that can disable your Loop App if you aren’t aware of the issue and don’t take action when changing time zones.

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. At a minimum, you should be going to your favorite support forum and reading the  posts at least once a week, or visiting this Announcements page at least once a week.

 Your Settings (IMPORTANT)

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.

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 the books “Using Insulin”, “Pumping Insulin”, “Think Like a Pancreas” 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. LoopDocs has a section dedicated to testing your settings prior to starting Loop.

If you are not comfortable with testing and adjusting your own settings with minimal hand-holding from your doctor, Loop is not for you.

Recently, there have been a number of people who have tried to Loop and have failed.  The most common reasons that people will fail in their Loop attempts are (1) failure to stay informed about Announcements in the Looped community; (2) having someone else build the Loop without understanding it themselves (e.g., paying someone to build the app for them or going to a “build party”.  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.  

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, and coming on the market “soon”. With the pandemic, “soon” has been changing for some of these, but right now, Control-IQ and Basal-IQ are available for the T-Slim pumps from Tandem Diabetes. There is an extensive write-up by someone who moved their child from Loop to a Tandem product on the SeeMyCGM blog. If you are weighing the pros and cons of Loop compared to a commercial system, I recommend reading that blog post before going any further. For people who do not want to invest in the Apple ecosystem, there is also an Android option available that you can read about on the web site. The Android and commercial options are outside the scope of this web site.



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

  • Do not pay someone to build it 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.

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


Your Journey To Looping

Consider this page as a way to step through your journey. The page was launched December 1, 2020. Another section with the next steps will be added each day or two by the moderators of the Loop and Learn Facebook Group for about the next 20-30 days until the document is complete. Enjoy your journey, no matter which path you take.

If you want to skip ahead and build today, please go to the official LoopDocs web site and start there instead.  Beware that LoopDocs is not updated regularly, if you get stuck on a step, come back to this document and look at the relevant day to see if there are any tips to get you over what you are stuck on.   Procedures change often, Loopdocs changes infrequently.

Day 1

History and background


Day 2

What does it cost?


Day 3 

Data, Data, What To Do With The Data?


Day 4 



Day 5 

Please take a moment to test your knowledge with a quick quiz and please answer the one question survey at the bottom of the Quiz.


Day 6

Community, Help, Information


Day 7 

What is a branch?  What is a fork?


Day 8

So Loop died, now what?


Day 9 

What are the Compatible phones for loop?


Day 10 

Tubed Pumps and Patch Pumps Compatible with Loop


Day 11 

Building Loop on a Virtual Mac


Day 12 

Compatible CGM’s

CGMs, or Continuous Glucose Monitors, as of this date are the following: (work in progress, apologies:)

Medtronic Enlite Generation 1. 

Libre 1 with Miau Miau

Libre 2 

Dexcom 5 and 6.




Day 13 

More on Settings.


Day 14

Initial Loop Set Up and Configuration


Day 15

What to Buy First?

I can only speak from my own experience. 

If you are on an old Medtronic pump, and have the old transmitter (and it is working!), and you have an iphone, then you will need either a Mac computer or to be able to download the Virtual Mac to your current computer. 

After you do that, you will have to purchase a Developer’s Account. At the time of typing, it costs $99 USD, and is essential for Looping. The alternative way is to not purchase the Developer’s Account and rebuild your Loop every week. I would highly, but highly, recommend purchasing the Developer’s Account, but both options are possible.

The next purchase you make will be the UN translator, a wonderful contraption called the Reily Link. This lets your phone, pump, sensor and watch all talk to each other. 

Day 16

Installing Xcode
Setting Xcode Preferences
Homebrew / Carthage


Day 17

Build Errors
Standard or WorkSpace


Day 18

Updating Loop


Day 19

Loop Operations (Displays)


Day 20

How Exactly Do I Use My Loop App?

  • Eating

  • Bolus

  • Overrides


Day 21



Day 22

Start Looping


Day 23

Flowchart BEFORE Looping


Day 24

Flowchart for Loopers

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