The Radio 1 DJ is one of seven celebrities who have taken part in the 100-mile expedition in aid of Sport Relief, alongside Strictly Come Dancing star Karim Zeroual, TV judge Robert Rinder and journalist Krishnan Guru-Murthy.
However, on Tuesday, Grimmy was forced to miss a 24-mile leg of the journey due to heat exhaustion.
“I’m absolutely gutted not to be with the team today,” he said on Tuesday. “I was mentally prepared for it but the medical team have decided I need to miss today.”
A day earlier, the presenter was forced to abandon a 35-mile cycle for the same reason, when he was close to the finish line.
Nick explained: “I got pulled by the medic just 2k from the finish line and treated for heat exhaustion. I’d been drinking, eating, resting regularly, but it came on so quickly.
“I feel much better today and I’ll be fine, but they have advised that my body needs to recover so I can rejoin the challenge tomorrow.”
So fresh-faced yesterday... Right before they actually started cycling! While 35 miles doesn't sound like much if you're a keen road cyclist, riding fat bikes across scorching hot sand is much MUCH more difficult🚲— Sport Relief (@sportrelief) February 25, 2020
Stay up to date with the challenge! https://t.co/N6Mztdpz8H pic.twitter.com/nCUFvbsAru
Sport Relief has said the aim of the expedition is to “break down the stigma of mental health” and “raise money for mental health services”.
The stars are aiming to have completed the 100-mile trek – via ski, bike and on foot – by Thursday.
Originally, the expedition was supposed to have taken place in Mongolia, but this was changed a week before the start date due to “ongoing coronavirus health and travel concerns in neighbouring China”.
This article originally appeared on HuffPost.