Running ultras with type 1 diabetes: “Just give me some sugar. It’ll be fine.”

Jonty Brown has learned a lot about navigating his sugar levels while running ultramarathons, including The Speed Project solo a year ago

It doesn’t matter how many ultramarathons I know about, or how many ultrarunners, when I hear about someone running hundreds of miles on their own, I think it’s an incredible moment in their lives. When I saw that Jonty Brown, a type 1 diabetic, was running The Speed Project solo in March 2025, I knew it was a great story.

It wasn’t the first running challenge that Jonty had embarked upon, though. Having only started running in 2020 during the UK’s Covid lockdowns after being tagged in a challenge, he soon thought, “I might as well do it every day.” That kind of thinking led to Jonty becoming the first type 1 diabetic to run across the UK just 18 months later in 2021.

Learning to fuel as a diabetic ultrarunner

But, yeah, he’s got diabetes. He was diagnosed over 20 years ago, as a tween. In this new age of running, where we have the science to meticulously calculate and maintain our energy expenditure and sodium levels, so we know the exact number of gels to chug down, how do you work wildly unpredictable sugar and insulin levels into life as an extreme endurance athlete?

“Running with type 1 diabetes… there isn’t a book for it. There’ll be a cure before there’s a book.”

“When I was first diagnosed, my nurse told me to just go out and learn. There isn’t an insulin to carb ratio for everybody – it’s completely individual, because your insulin sensitivity will change throughout your life. It’s all about just getting out and trying, so trial and error is the only way.”