Journal: my start on Loop

I just started Loop last week. I will keep track of everything that happens to me here, in case it can help others.

I will start another thread for the setup that we did (mostly my mother).


My first, aborted start with Loop in 2018

It all started in spring 2018, before we left the Midwest for 15 months in Europe. We had decided to start Loop while we were there. I use an old iPhone SE (several, really, that we purchased used because I am rough on my phones). My father purchased a MacBook Pro to be able to program Loop. A super nice member here gave us her compatible Medtronic pump (that was SO nice!), we bought a RileyLink and we left the Midwest.

After a summer on the road, we settled for a while in Southern Spain. My father connected the Mac, which updated and bricked itself right away. It took us 4 months to figure out out to get it going again, with very little connectivity and in the small town with little technology around us. Right after that, we went to spend 2 weeks in South Africa. I took the Mac with me. We got carjacked and fought back. In the process, the MacBook got really mangled: I was fighting over it with one of the carjackers and I won, but the MacBook was very damaged. So that was the end of Loop for that year abroad. But we had read that Omnipod was now a possible target for Loop, and that was really exciting, since that is what I am using.

We came back to the US for the beginning of the school year in September 2019, in Berkeley, CA. Moving our possessions from the Midwest and unpacking them took a long time, till about Christmas. Then we found the MacBook in February and had it repaired. Right then the pandemic started, everything changed, and we started So there was another delay.


Getting ready for Loop

This year, in 2020, the school year ended in June. My father was still very busy with HelpBerkeley (it is more than a full time job), so my mom took over the planning for Loop: I wanted to have some experience of Loop before I went back to school this fall. She did most of the work to set it up, and I studied the links she sent me. We had to buy another RileyLink because there are different frequencies needed for OmniLoop. Finally, we had everything ready last week: We had compiled and loaded the app in my iPhone SE (it is an old iPhone SE, and it carries an old iOS version, 13.6 but the latest that the old SE can carry), and set up a Nightscout account.

We had found out in Loopdocs that it was really important to start with good parameters, so the next step was to make sure of the settings. In the mean time, on Monday 7/20 I started going openloop with Loop, in order to get accustomed to the software, but still calculating my own boluses and corrections.


Loop settings

Until March 2020, I had been keeping really good logs of my dosing and carbs, using MyNetDiary, ever since I had been diagnosed (that was more than 4 years ago: my diagnosis was on May 2, 2016). And, of course, I have Dexcom Clarity data since I use a dexcom CGM.

But, since the Shelter-In-Place (SIP) started, I had not done such a good job: our life had lost its structure. So, when I had to select my Loop parameters, I had to do some more testing.

I knew that my Basal was 1.0U, because I am flat most nights after the last of the day’s IOB and COB is gone. So that was good data.

We had experimented, years ago, with DIA, and we felt comfortable at the time that 5 h and 45 minutes at the time. But, when I got into puberty, I started stacking insulin to get my peaks down, and we found out that, with major stacking, we see longer DIA (because I could still run low after more than 6 hours). So, based on how long after my last insulin injection I can go low, I figured that my DIA was really 6.5 hours.

I had used 1:12 as ICR for a while. I did more experiments and came up with 1:9.5 to 1:10.5 as a better number.

ISF was the most difficult one to figure out. Daytime, I always had used 1:25 for the past 2 years. But my hormone peaks don’t react the same way, and I often have to do 1:15 or even 1:8 to bring them down. And, to be honest, during the day I go up and down a lot, and inject a lot of insulin all the time: it is really difficult to take out IOB when looking at numbers. In the end, looking at nighttime corrections when there is no IOB or COB I came up with 1:25 as the right number. With that, I thought I had a good set of numbers.


You sure you aren’t talking about your I:C here? 1 unit can bring your BGs down as little as 8 points?

Liams ISF ranges from 1:180 to 1:230. You must be very insulin resistant if 1 unit brings you down by so few points!


The eye of a Loop expert

In March, my endo at Oakland Chidren’s Hospital had put us in touch with a super nice endo (I will call him Roger because I don’t know if he wants even his first name mentioned) who does research on Loop at Stanford. He told us that he had helped hundreds of people start with Loop, and that the parameter tuning is hardest–so we asked him to look over our settings before we started.

Roger did not like them at all. He is able to compute all expected numbers from TDD and weight (I will discuss these formulas in another thread). He thought that, with the TDD I had (about 55), my ICR should be much higher (in terms of insulin, so more like 1:7.5) and my ISF should be much lower (in terms of insulin, so more like 1:30 or more). In the end, I started, at his recommendation, at a Basal of 0.95U (a touch lower than my regular one of 1.0), an ICR of 1:7.5, and an ISF of 1:30. My target would be 112-125mg/dL, my max bolus 12 units and my max basal 6 units/hr. That is how I closed the loop on Wednesday.


Yes. I use 1:25 in general, for food peaks, but, when I am on a hormone peak, it is much worse, and it can be up to 1:8. I often use 15-20U to come down from a bad hormone peak. My record is 30U. It is not fun.


Great job posting your journey !! I took the easy route and waited for pump warranty to end, and switched to Tandem X2 just a few weeks ago.

Congrats on your dedication and finding a great doctor. Looking forward to the next chapter!!


That is great! My friend Julia has been on the X2 for more than a year, and she is having no lows at all :slight_smile: How do you like yours?


Awesome summary @Kaelan! Look forward to hearing how it works for you.

I suspect we talked with this same doctor as well, who suggested a dramatically lower (aka stronger) ISF and said the basal rate was basically irrelevant. And for a while we tried it, but it did not work well during the day; Samson was crashing heavily if the carb ratio was even slightly off, for instance. However, it was the impetus for us to be bold with our nighttime resistant highs, so the number he suggested for ISF wound up working overnight and is what we stuck with.

I’ll be curious how it works out for you in comparison to your other settings.


Getting used to differences in infusion sets and reservoir filling, but really like the pump display with cgm data. Still tweaking settings but overall happy with it, and the great advice I’m getting from other online users.


And right here we figure out you aren’t in the normal category anymore. Holy hell that is quite an experience.


@Kaelan was quite literally fighting for his life.


Thank you for sharing your experience and thoughts so clearly and eloquently. It’s nice to hear the details about the whole process.

I look forward to hearing more from you about your Looping journey. It always amazes me how different we all our with settings for our D tech stuff…I learn so much here!!



What was the rationale? Or was this applicable only to pediatric patients?


I think the idea was that if the Loop was constantly calculating a new temp basal and the ISF was very strong, it’s constantly turning on and off in response to smaller changes in blood sugar, and so it effectively means you’re almost never using your baseline basal rate. I also think some of the commercial algorithms don’t heavily rely on an assumed basal rate; they’re assuming there is only one number akin to insulin sensitivity that is basically an amalgamation of things that tend to make your blood sugar rise (food, hormones, underlying basal insulin needs)and things that tend to make your blood sugar fall (insulin on board, exercise, hormones, etc.).

But of course, in the end, we found it didn’t work so well because Loop is built on the assumption of a set basal, and all the calculations are based off of that. I think that there is probably a way to model it as a dynamic system with a certain parameter space, where if your ISF and CR and basal rates are in certain ranges, you can reduce down to one or two of those and still have things work just as well, but maybe in other parameter spaces you can’t. Just my guess.


Interesting! Thank you.


Loop Take-Off: tuning settings

The first few days, I had to adjust some parameters up and down. I consulted Roger, the endo, every time. I went up and down with my ICR. I had started at 7.5 which seemed like a lot of insulin for me: I went up to 8.5 after a couple of days. I went up and down 5 with my ISF.

Early on, I saw a characteristic Loop phenomenon where I was going up and down at night (the 5U injection is a bad event log that I don’t know how to correct, it didn’t happen):


The normal explanation in Looptips is that your ISF is too high and you overcorrect all the time. This led me to create two segments, one for midnight to 6am and one for the rest of the day, and to lower my ISF at night: that took care of it.

First week results

Over the first week, my % low went down a lot, from 17% to 7%. My calculated A1c went up a bit, from 5.8% to 5.9%. My in-range percentage (70-180) went up a bit from 77% to 82%. My standard deviation is still the same, about 40. I am using less insulin overall, probably 5-10U less per day. I am hardly using any correction carbs (I used to use about 30-40 correction carbs per day, although it changed a lot every day).

It is really nice not to have to wake up at night: makes a big difference. But I am a bit frustrated because I stay high too long and Loop doesn’t bring me back as fast as I would like. Of course, this is also probably why I don’t go low. [I am writing this a week later btw].


We had this issue as well until we switched to the freeaps (microbolus) branch. The micro boluses are amazing at keeping the bgs in a specific range the whole night. You should check it out.

Basals take far too long to bring bgs down.


That is a pretty darn good looking track. Hard to believe that just a few years ago you and my son were riding the roller-coaster almost every day. I hope you dad is finally getting some sleep at night.