Basal Not Basil

Things I've learned while parenting a child with type 1 diabetes


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Any time I post about Hazel using Loop, I get a lot of questions. This is my attempt to answer all those questions in one post. 

What is Loop?

Loop is a DIY (do it yourself) hybrid closed loop system. It is comprised of a continuous glucose monitor (we use a Dexcom G6), an insulin pump (we use a Medtronic 723), a RileyLink, and an iPhone running the Loop app. Very simply, Dexcom sends the glucose data to the phone via bluetooth. Loop looks at the glucose data and sends a message to the pump to adjust the amount of insulin it is pushing. RileyLink is a little translator making it possible for the phone to talk to the pump and vice versa. You can read the complete history about how this came to be here.


Here is a very poor drawing of how it works. I should say one of my children drew it, but honestly it would look better if any of them did. Art is not my forte.

How do you use Loop?

Loop is controlled completely through the iPhone. I enter all of the settings in the app (carb ratios, ISF, basal rates) and then it saves it to the pump. When Hazel eats anything, I enter the type of food and how many grams of carbs she’s eating into the app. It recommends a bolus based on her blood glucose level, the absorption time of the carbs, insulin already in her system, carbs already in her system, and her carb ratio for that time of day. Basically it does all the math for me. For foods that have a longer absorption rate (pizza, pasta, foods high in protein, etc) Loop will extend the bolus, suspending insulin delivery if blood glucose is trending down.


This is what the Loop interface looks like. It’s so much better designed than any other diabetes tech I’ve encountered.

 How can I get Loop?

Great question! If you are interested in building your own system, I highly recommend joining the Facebook group Looped and following Katie DiSimone on Instagram (@kdisimone). All of the information about how to build the app and how to use Loop can be found here.  You can find which pumps are compatible, all available details about Omnipod Loop, and everything else you need to know about Loop. These documents are amazing. We refer to them often when we are trying to trouble shoot an issue. Sometimes I just read them for fun because they are that awesome.

When will a public (non-DIY) version be available?

I don’t know when, but Tidepool is working on a non-DIY, FDA approved public version. With Tidepool Loop, one could simply download the Loop app (as opposed to build it yourself) and a RileyLink will not be necessary.

Why don’t you just use the Medtronic 670g system?

When we first started Hazel on a pump this system was not an option for her due to her small insulin needs and age.  Now I believe it is an option for her, but not one we would be interested in pursuing. While it is great for some people, I think we would find the lack of customization frustrating. The 670g has two options for a target: 120 and 150. Also, with this system you have to use Medtronic’s cgm. It is less accurate than Dexcom and requires regular calibrations. Finally, the 670g is not optimized for someone other than the wearer to be operating it. We actively work to have diabetes be less of a burden to Hazel. The 670g would increase the burden on her as we would have to interact directly with the pump that was attached to her multiple times a day.

Why are there no cute pictures of Hazel on this post?

Fine, here’s a picture of Hazel.



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