Lynne Stevens, 63, of Yaddlethorpe, was given a second chance at life a year ago after Anne Gilhooley, 63, of Liverpool, made the sacrifice.
A year after the operation the pair are celebrating and letting others know what a difference organ donation can make.
Lynne was diagnosed with kidney failure in 2005. Her condition deteriorated to the point where she did not have the strength to change the bed sheets and she needed a dialysis machine to remove waste from her blood four times a day.
Lynne's husband Dave was told his blood pressure was too high for him to safely donate one of his kidneys, and Lynne refused to let her son give up one of his organs to help her.
But when an old school friend, who Lynne had known for more than 50 years, learnt of her illness, she insisted on helping.
Anne turned out to be a perfect match for Lynne.
And a year after a successful transplant operation at St James' Hospital in Leeds, the pair are urging people to give the gift of life by considering organ donation.
Lynne said: "The past 12 months have been a joy for us.
"Before the operation, I didn't have any kidney function and in 2008 I started to get really ill.
"It got to the point where I couldn't change the bed sheets and Dave had to help me an awful lot. It just wasn't nice.
"I got really emotional when Anne offered to donate one of her kidneys and I still can't believe what she's done for me.
"She's just given me a second chance at life."
Lynne said she did not want to put Anne's family through the stress of an organ transplant, but Anne was determined to help her friend.
"She just did it and I can't get my head round it," said Lynne.
"She's got children and a husband and I thought they might try to dissuade her, but they were so supportive.
"She said she saw me going downhill over the five years, as I was always quite vibrant and organised trips out for the group of us, but that just petered out.
"That's when she said she decided to step in. "She's just wonderful."
The pair are now closer friends than ever, speaking on the phone at least four times a week.
They are meeting up this weekend to celebrate the first anniversary of the operation, and Anne said she would do it all again.
"We're lifelong friends, so it didn't enter my head not to donate my kidney to her," said Anne. "Seeing Lynne on dialysis four times a day was soul- destroying.
"I wouldn't change anything I've done and I would do it all again."
She said she has had no negative effects from the operation and is urging people who are considering donation to help a loved one to go ahead with it.
"There were absolutely no side-effects and I know the doctors wouldn't have taken the kidney if it put me at risk," said Anne.
"We're completely different. I'm little and she's large, but we were a perfect match and she's got a part of me in her now."
This week is NHS Transplant Week.
More than 10,000 people are currently waiting for a transplant in the UK, and on average three people who need a transplant will die each day.
To help a friend with kidney disease, ask them to put you in touch with the hospital who can run tests to see if you are a suitable match.
To sign up to the Organ Donor Register, call 0300 123 23 23 or visit the website, organdonation.nhs.uk
Photo: ULTIMATE GESTURE: Lynne Stevens (right) with friend Anne Gilhooley (left), who donated a kidney