Vicky Phelan wasn't able to attend the Late Late Show on Friday night after not feeling well enough in the last few days.
The Cervical Check campaigner told RTE viewers how her hair is now growing back, but it hadn't been a great week for her.
But the Kilkenny woman is hoping she will be well enough to climb Croagh Patrick with Charlie Bird in April for multiple charities.
In a video message to the former RTE broadcaster, Vicky said: "Hi Charlie, Hi Ryan, I'm really sorry that I could make it to the studio tonight to be with you to launch a climb with Charlie, but I'm just not feeling well this week.
"Charlie, I sent you a text earlier in the week, so you'll know.
"I'm feeling a little bit better now in the last couple of days as you can see, my hair is starting to grow back, which is great, but I'm just not feeling well enough, but I really want to send you all my love tonight I hope you get a huge amount of support after your appearance tonight for your climb in April and please god all going well ill be there with you in April."
Vicky will also appear on RTE Radio One's Sunday with Miriam O'Callaghan shortly after 10am.
