Lisa says she has no regrets
When Lisa Simmons heard her younger brother needed a kidney transplant she did not hesitate - immediately offering him one of hers.
Having lost both her parents, she is very close to 29-year-old Tim and said the decision had been an easy one to make.
"The waiting list, we were told, could be up to eight years," said the 32-year-old PA, from London.
"I just wanted him to have the transplant. The thought of him having to go onto dialysis and wait...
"I would never have been able to sit back and watch and not do anything."
Tim said his sister's gift had saved him many possible years on dialysis.
"It is the gift of life," he said. "I would have seriously struggled without it."
But Tim said he had not originally told his sister that he was ill.
"I did not tell her for six to eight months, and it was only when she found my medication that she realised there was something wrong.
"I had to confess and she said she would give me a kidney."
Tim knows he is one of the lucky ones - others are not so fortunate.
Tim has won medals for his cycling
Currently, 8,149 people are waiting for an organ transplant in the UK and last year (April 2008-March 2009) 6,481 organ transplants took place. But 465 people in the UK died last year while waiting for a donor.
New research from NHS Blood and Transplant (NHSBT) shows a divide between those who think they have already signed up to be an organ donor and those who are actually registered.
In London, a recent NHSBT survey revealed that 29% of people think they are on the organ donor register, whereas the actual figure is 23%.
An NHSBT spokesman said "living donations" like Lisa's, which was carried out three years ago, were literally a life-saver.
"Their gift means people can give up dialysis and other costly treatments, so they are also freeing up NHS resources for others in need."
But, despite being a "perfect match", Lisa said it had not all been plain sailing. Doctors told her she had to lose weight before the operation.
"I lost 4.5 stones (28.58kg). It was a struggle. I gave up drinking alcohol for 18 months, did not have any junk food or fizzy drinks," she said.
She said the operation went very well and she would do it again if she could.
"The pleasure you get out of making someone so much better just blows you away - it still blows me away," Lisa said.
But she said there had been some unusual side effects - and not just for her.
"He did not like curry," she said of her brother, "but now he loves it like me, which is strange."