
Even before 13-year-old Drew Mendelow of Maryland was out of the hospital with a new type 1 diabetes (T1D) diagnosis, the wheels in his young mind were already spinning on how to better manage this chronic condition with technology.
His September 2020 diagnosis came out of the blue, even though his maternal grandmother has been living with T1D for years. But there at Children’s National Hospital in Washington, D.C., the teenager knew immediately that life would be different going forward with constant daily juggling of insulin doses, food intake, and monitoring activity and glucose levels.
Yet in his early post-diagnosis hours, Mendelow discovered that a mobile app or diabetes tool with everything he needed was not available. So, he started creating his own technology.
An avid video gamer, he had just begun learning coding skills, prompted by the COVID-19 closures and cancellations of his usual summer activities. Within weeks of his diagnosis, his drive to create his own digital disease management tool materialized in the form of an app he named T1D1, for Type 1 Diabetes from Day 1 — as in having the right solution right out of the gate.
“The app is for those who are newly diagnosed and don’t have a pump, whether they can’t afford one or don’t want one at that point,” the teenager says. “It’s really to make life easier to help track everything.”
Available for free on both the Apple Store for iOS and Google Play for Android, this new T1D1 app is at its foundation a bolus calculator and food and glucose log.
It has an easy-to-use, intuitive interface, but is in fact a quite sophisticated tool. Multiple screens display different functions:
- Blood glucose (BG) log shows time and results, in both the American unit measurement of mg/dL and mmol/L for the European crowd
- Food library contains carb counts, at various portion sizes, and a way to easily tag BG results as meal-time readings
- Insulin dosing bolus calculator cross-references with the user’s BG ranges and varying insulin sensitivity and carb ratio settings
- Detailed notes section
- Optional negative/reverse correction factor, to tweak insulin doses if there is already Insulin On Board (IOB) or if the user is already low
Although it doesn’t currently connect with continuous glucose monitor (CGM) data, that’s an idea the Mendelows are considering for the future, along with adding the ability to upload photo images for the food database and other capabilities.
While it was Drew who had the initial idea and started the coding, his dad tapped into his professional knowledge to help out. Mike Mendelow works in IT development for the real estate industry, though he notes that helping to create T1D1 was his first time writing an app.
The family began helping Drew realize his vision first by “logging everything” in a number of Excel spreadsheets. But soon a first iteration of the app was ready, and they could start using their own D-experiences to revise it.
Although T1D1 has only been available since Fall 2020, the Mendelows are using the reviews and D-Community feedback — as well as their own learnings, of course — to expand and generate new features. As of early December, it had been downloaded over 10,000 times.
One of the common comments the family has received from early users that makes them most proud: “It’s obvious a T1D developed this app.”
Other mobile apps launched over the years do include some of the same features, and we at DiabetesMine have covered many of those digital diabetes tools as they’ve come and gone.
This new T1D1 app seems to nicely fill a gap for the newly diagnosed that the Mendelows say they were looking for in those early days.

While they were blindsided by Drew’s diagnosis, the Mendelows’ family connection to the chronic condition helped. Drew’s grandmother (his mother Laura’s mom) was diagnosed over a decade ago with T1D in her early 60s. Drew had already seen her using an insulin pump and CGM.
“My mom helped guide us, and it helped at diagnosis so this didn’t feel as overwhelming as it could have,” Laura Mendelow says. “He knew his grandma has this and it wasn’t so foreign, because he saw her living with it and being active and happy. She has been a good role model for someone with type 1 in managing diabetes well.”
The teenager’s energy impressed even his medical care team at Children’s National Hospital, including his pediatric endocrinologist Dr. Brynn Marks.
She recalls that first day of diagnosis when she found the young patient discussing limitations of existing insulin dose calculating apps with the healthcare team. He told the doctor his plan to build an app to address the unmet needs of the diabetes community. And a few weeks later, he reached out to the medical team for help beta-testing the new app.
In her clinic, Marks said she has several families using the new app to double-check their insulin dose calculations in those early days of life with T1D — an especially important time because there’s so much to learn so quickly.
“At a time that some may have been at their worst, Drew chose to make the best of a new life challenge,” Marks tells DiabetesMine. “Thinking beyond himself, Drew is focused on making a tool that will empower everyone with diabetes to optimize their own management. It’s truly been an honor to work with him on this project and I have no doubt that there are even bigger and better things to come from this impressive young man.”
Drew started on injections, but just before Thanksgiving, he transitioned to a Tandem t:slim X2 insulin pump. That therapy change meant tweaking his app, using it less for insulin dosing calculations since that’s a function built into Tandem’s Control-IQ algorithm.
These days, Drew says he is using his new app largely for the food library to track carb amounts for his favorite meals.
The family is currently working to translate the mobile app into Spanish and Chinese, and they point out it’s important that it remains ad-free without any necessary in-app purchases. They’ve built the app from donations and they’re donating any extra money made to the JDRF to make a difference.
“There shouldn’t be any barriers to tracking diabetes data, because everything costs so much already when you have diabetes,” Drew’s dad Mike Mendelow tells DiabetesMine. “We want this to be accessible to everyone who wants it.”
The Mendelows say they’ve also been talking with open-data organization Tidepool about connecting this mobile app to their online hub, which synthesizes data from different glucose meters and diabetes devices into one place.