In the fog of new parenthood last winter, Cory Zapatka reached into his closet in his New York apartment and felt his stomach drop. "I went to change my infusion set,” he remembered. “And I was like, ’You've got to be kidding me.’ I have one left."
His daughter Edie was three months old at the time. Exhausted and on parental leave, he missed the refill reminders buried in his work email. For the next two weeks, he switched to multiple daily injections while juggling life with a newborn.
Zapatka has lived with T1D for 22 years, since his diagnosis at 15. He navigated T1D through high school, college, a career in filmmaking, his current job at Notion, marriage, and now fatherhood. In all that time, he managed his supplies the way most do: imperfectly, relying on a patchwork of Post-it notes, email reminders, and memory.
It worked well enough until last January, when he ran out. A mistake that ultimately led him to build a solution, and by spring, his supply management app, Stash Diabetes, was live.
Success came quickly: in the few months it’s been available on iOS, it's had 3,500 users across 62 countries — all from word of mouth without advertising. Users have scanned more than 35,000 items into the app, and an Android version is in development.
The mental burden of living with T1D extends beyond counting carbs, monitoring glucose, and taking insulin. It also includes the invisible work of tracking life-saving medications and supplies.
"You don't notice it when you are dealing with it every single day, but managing your supplies is such a big part of the disease," Zapatka said. "You have the clinical side — but there's this whole other part of your brain that manages the logistics."
For Zapatka, as he suspects is the case for most, managing supplies was always an inexact, often haphazard, and stressful process.
"For the past 22 years, I was taking inventory on a Post-it note or in a notes app on my phone,” he said. “It was kind of never really up to date."
Looking back, he realizes he had been fortunate not to have a problem until his daughter was born. He had good insurance, a supportive family, and enough financial stability that his informal diabetes supply tracking system never fully broke down.
But when he needed a new system and searched the app store, he was amazed to find that none existed. So, he built one.
There was one problem: Zapatka wasn’t a software developer.
He studied film at the Rhode Island School of Design, worked in media, and now works in product marketing at Notion, the workspace platform.
Using AI coding tools, he taught himself to build Stash’s first prototype. His outsider perspective became one of the app’s greatest strengths.
"If Dexcom were to release an inventory app, it wouldn't support Libre,” he said. “If Tandem released an app, you would only be able to track Tandem supplies, and it wouldn't be able to cover the vast majority of all of the supplies that people need to use.”
Zapatka said he suspects that’s why a universal supply tracking app didn’t exist before Stash: “It had to be an individual, someone living with the disease, to build it."
Not only is Stash ecosystem-agnostic, but it also reflects the learned lessons of the founder’s two decades with T1D.
"There's a lot of conditional logic that comes from my experience living with diabetes that's built in," Zapatka said.
For instance, every time a user deducts an infusion set, Stash automatically deducts its associated cartridge, tubing, and refill syringe from inventory. Alcohol swabs also auto-deduct with sensor and infusion set changes for the same reason.
The app tracks more than inventory. It also monitors expiration dates, records injections and infusion sites, helps users plan for travel, shares recall alerts — and collects community reports tied to specific lot numbers or supply-related issues that users report when things go wrong.
"Stash is very calm by design. It will only give notifications when they’re needed,” he said. "It's actually consolidating the amount of places I need to look.”
Since using Stash, Zapatka has turned off the reminders on his Tandem pump, since Stash shows him his infusion set stock more easily.
Zapatka built Stash for himself and people like him, but he’s seen it used in ways he didn’t expect. "It's really been amazing to see parents using it to manage their children's inventory."
Zapatka points to research suggesting technology will play a growing role in that transition and help “set them up for success when they're actually on their own."
The use cases keep expanding. People with type 2 diabetes use it to track GLP-1s and oral medications. Young adults are using it to monitor aging parents' insulin supplies. "It kind of flips,” Zapatka said. It's a multi-generational tool.
In the diabetes device world, product failures often leave users guessing. Formal recalls can come months after they started noticing something was wrong. The recent Omnipod recall, Zapatka said, is an example indicating an unmet need.
"People were complaining about Omnipods leaking for months and months,” he said. “And they were told, nothing's wrong, keep using them. And then six months later, there's a massive recall affecting 7 million units. People are saying, ‘I knew it.’"
Zapatka realized that Stash’s users can crowdsource this kind of information to help identify patterns that no single user could see. The app’s community reporting feature, launched in June, allows users to flag device failures or supply issues such as sensor issues, bent cannulas, insertion failures, or suspect insulin, and link them to specific lot numbers. The data is de-identified and aggregated, meaning Zapatka can’t see who submitted them.
“If we have, say, 10 different reports from 10 different people in 10 different parts of the country, that would probably warrant a gentle notification that says, ‘Hey, just a heads up that we are receiving a higher than normal number of reports for this lot,’” Zapatka said.
In the first six weeks, Stash recorded over 260 reports of device failures or supply issues. Zapatka said he doesn’t want the app to replace manufacturer reporting, and users are encouraged to always contact the company directly, but he aims to give people something they’ve been missing: confirmation that the problem isn’t isolated and they’re not alone.
As Stash grows, Zapatka is working to build a sustainable data model that supports the app without compromising users’ trust, using Tidepool’s approach to data as a guidepost.
“Using this data to find patterns within the community and using it for good," he said, “using it for research and to find better clinical outcomes for people with diabetes.”
He envisions sharing aggregate findings with manufacturers to help improve diabetes devices and supplies.
"You can use this app for free and not contribute any data, and that's totally fine,” he added. “But what I have found is that there's actually a pretty large cohort of people who feel comfortable giving anonymous data because it does get fed back into the community to help others."
Zapatka is committed to keeping Stash free. "I'm not in this to make $5 a month off of people with diabetes."
That community-first philosophy goes back to his own childhood.
Growing up, Zapatka went to diabetes camp every summer, a place where he could be around other kids who understood his daily life. The rest of the year, he remembers, he was on his own.
"The disease itself is very isolating,” he said. “You often feel like you're the only one struggling. If there's a recall, you feel like you're the only one burdened by it."
Stash was built, in part, to counter that feeling. One small example appears on the app’s dashboard: beside the insulin vial counter, users can see how many others have open vials of insulin with the same lot number.
"Every time I use a vial of insulin, I think, ‘This is my little vial, it doesn't belong to anyone else,’” Zapatka said. “But there are so many other people in the world dealing with the same disease. And just that little hint that says, ‘You're not alone,’ I think can actually go a long way."