Harry Judd has been diagnosed with a heart condition.
The McFly drummer is "really annoyed" after discovering he has an ectopic heartbeat - which is also known as a 'wandering pacemaker' and means the rhythm of his heart has missing or extra beats - following his intense training sessions for next month's London Marathon.
In a series of posts on Twitter, the 27-year-old musician wrote: "So I've acquired and ectopic heart beat through excessive exercise. It's known as a Wandering Pacemaker commonly seen in athletes ... it takes causes symptoms or requires treatment. Still it's really annoying!!!
"It proves I've even pushing as hard as possible for the marathon + if u've been thinking of sponsoring me then surely that will pursuance u? (sic)"
While the condition is common and usually doesn't require treatment, Harry - who is running the 26.2-mile race on April 21 for the Teenage Cancer Trust - admitted he needs to "chill out a bit".
He tweeted: "It's nothing to worry about but just means I have to chill out a bit :-/
"Athletes get it though :-) (sic)"
As well as the marathon, Harry is also due to tackle a 13-mile assault course in two weeks to raise money for the Teenage Cancer Trust and the Eyes Light Appeal - in aid of The Brain Injury Rehabilitation Trust (BIRT) - which was set up by his wife Izzy Judd and her family after her brother Robert was badly injured in a road accident in 1997.