Ten-year-old Elise Chaundy has been in and out of hospital since she was born.
The North Kidlington Primary School pupil was unable to keep food down as a baby and spent much of her first 18 months in hospital.
Then, aged four, she contracted numerous infections and spent the next few years on antibiotics, undergoing tests.
Doctors conducted a number of scans but could not find any serious underlying condition.
Now, Elise, of Brandon Close, Kidlington, has made a good recovery.
Her mum Michelle Miller, 31, a ward clerk at the John Radcliffe Hospital’s heart centre, has signed up for the OX5 Run around Blenheim Palace in Woodstock on Sunday, March 25, to raise funds for the children’s hospital to say thank you.
Mrs Miller said: “You would think Elise would be elated that she no longer has to go to the children’s hospital but it has become a place she really loves.
“The hospital visits always felt like fun to her because the staff were so fantastic and the facilities were so good.
“There was never any fear factor for her because the play specialists always made her feel so at ease.
“As a parent I felt so confident with the staff because they were so reassuring.
“Elise has never let her medical problems get in her way and we have never wrapped her up in cotton wool. We have a lot to be grateful to the hospital for and this is my chance to do something positive.”
Mrs Miller has already been out on a number of training runs and as an Oxford United season- ticket holder hopes to be part of the 100-strong team of fans who will be running the race.
She added: “I have never done the OX5 Run before but I quite like running so I think I should be okay completing the course.”
Elise said: “It’s really nice that my mum is running. I don’t think she’ll be fast, but I am very proud of her for taking part.
“I did like hospital because the nurses were all really nice and smiley and made me laugh.”
So far, 400 people have signed up for the five-mile race.
Last year, runners raised an estimated £60,000 for equipment the NHS cannot provide.
This year they are hoping to raise £100,000.
Find out more or sign up at ox5run.co.uk