[Health Tech Live! Join us online at 8 a.m. Wednesday, July 26, for a special Facebook Live stream of GeekWire’s next Health Tech Podcast. Sign up to be reminded here.]

Dana Lewis has Type 1 diabetes, which means her pancreas doesn’t work the way it should: It doesn’t make the insulin she needs to survive.

So, she built a new one.

It’s not a biological organ. Lewis’ artificial pancreas system (APS) is an open-source computer system that monitors her blood sugar level and gives her body insulin as needed, building on the insulin pump and glucose monitor that she’s been using for years.

Now, Lewis is known as the founder of the open source APS and leads a community of DIY diabetes patients who are constantly innovating new technology to help manage the condition.

She’s built a technology that is already changing and saving the lives of people with Type 1 diabetes, and she made it happen years before commercial devices have reached the market. We tell her story on this new episode of the GeekWire Health Tech podcast.

Lewis started working on OpenAPS two years ago, and at first, she didn’t intend to build a computer system at all.

Like thousands of other people with Type 1 diabetes, Lewis was using a continuous glucose monitor to track her blood sugar level around the clock. When her levels were too high or too low, the monitor would sound an alarm to let her know she should inject insulin using her insulin pump.

But Lewis is a power sleeper. She slept through the loudest alarms that her monitor makes, which meant she could slip into a coma or even die in the middle of the night because her blood sugar was dangerously high or low.

“I had to rely on my mom texting or calling me in the morning to check and make sure if I was OK,” Lewis said. “You don’t want it to be the thing that worries her — about whether you’re going to be alive in the morning.”

Lewis knew how to code in C++ and Fortran 90 thanks to an honors program she took in college, so she set out to program louder alarms into her monitor.

But as she worked on her project, she realized there was much more that she could do to make managing her diabetes easier.

For those of us without Type 1 diabetes, it can be hard to imagine how much work goes into managing the condition. Lewis said she is constantly checking the data on her glucose monitor, doing math in her head about what needs to change, and then reprogramming her pump to give her the amount of insulin she needs.

“Throughout the course of the day, a person with type one diabetes might make something like 300 decisions about things that impact their blood sugar and that includes numerous looking at devices, doing math calculations and pressing buttons on their pump, or if they’re not at a pump, doing multiple injections throughout the day,” she said.

“It’s not a precise science,” she said. “Today, my insulin sensitivity level — how one unit of insulin impacts by body — might be one thing, but in two days when I’m in Europe and jet lagged and haven’t been exercising for two days, that might be different. So you’re constantly dealing with everyday changes and how it affects your body.”

And because she can’t keep track of her blood sugar level around the clock, her levels would still spike or drop without her noticing, when she was exercising or after a big meal, for example. She would only realize afterward when her monitor sounded the alarm.

So Lewis thought: Why not program a computer to keep track of this? She teamed up with her boyfriend to develop an algorithm that automates all the math she does every day and also takes initiative to stop her blood sugar level from spiking.

Now Lewis’s APS monitors her blood sugar around the clock and reacts with very little input from her. It’s made up of her glucose monitor, her insulin pump and a small hardware rig built on an Intel Edison computer.

“I went from being afraid to go to sleep at night and having to text my mom every morning as my safety balance to — I don’t have to do that anymore,” she said. “Until you have that fear, it’s really hard to articulate what a burden that has lifted off of you.”

“It’s not a cure, but it helps so much and it cuts down immensely on the number of lows and highs that I experience, and that security is just priceless,” she said.

Lewis was so excited about her APS that she decided to share it with others. She couldn’t distribute the hardware itself without jumping through regulatory hoops, so she decided to make all her code open source and has become the world expert on building OpenAPS.

She estimates that about 400 people around the world now use OpenAPS, and that number is increasing as more and more people find out about the system. It’s not the right solution for everybody, but for people who don’t want to wait for a commercial option, it can be a huge relief.

Until you have that fear, it’s really hard to articulate what a burden that has lifted off of you. In October of 2016, the FDA approved the first ever commercial artificial pancreas for the U.S. market, developed by a medical device company called Medtronic. It is just now rolling out to the market, and estimates put the price at about $8,000, with patients spending additional thousands of dollars a year in disposable cartridges.

While commercial devices look like they could be prohibitively expensive, even with insurance coverage, an APS offers a cheaper alternative for people with existing pumps and monitors or those buying second-hand equipment. It’s just $150 for the additional hardware, and often just a few hundred dollars for a second-hand pump or montior.

Lewis says the community is always finding ways to make the technology accessible to those on a tight budget.

But she says that OpenAPS also has distinct advantages over closed commercial systems.

“What we’ve learned is that no commercially approved system is going to make everybody happy,” she said. “The first generations are very conservative and it’s likely going to be the second or third generations of those commercial systems before it reaches the caliber of what we’ve been able to innovate on our own.”

Those commercial systems also likely won’t let patients personalize the system to their needs or pull their data onto a smart phone or watch, all things that the OpenAPS can already do.

One day, there may be a commercial system that works as well as OpenAPS does for Lewis and other diabetes patients. But in the meantime, Lewis plans to keep building and improving on the system.

Find more Health Tech podcasts at GeekWire.com/healthtech, and subscribe on iTunes, Soundcloud or wherever you listen.