Mrs Berry has been cleared for the procedure after losing two stone
A woman from Oxfordshire is preparing to be the first in the county to take part in a paired kidney donor scheme.
Diana Berry, 52, from Oxford, cannot donate a kidney to her ill son, who has chronic renal failure, because their blood types are not compatible.
But under a new system, she will give one of her kidneys to a stranger with somebody else's organ going to her son.
The procedure was made possible after laws introduced in 2006 allowing live donations from strangers.
Mrs Berry's son, Matthew, 24, has to use a dialysis machine every day and she said a transplant would change his life.
Over the past eight months she has had to lose two stone in weight and has given up alcohol in a bid to make her an eligible donor.
She said: "I am doing it so that he has a chance for life and we can all get back to normal living as a family.
"I sacrificed a lot to do it, like losing weight, but he is worth everything to me me."
Mrs Berry has now been cleared and her details have gone into a database of potential donors.
Next month a computer will analyse their details.
If matches are found, Mrs Berry could donate within a month, and her son would receive an organ within 24 hours of his mother's operation.
"We're hoping it won't be too long now," she added.
"There is still the chance of getting an organ from someone who has died, so whatever comes up quicker we're just keeping our fingers crossed."
The Paired Share Transplant Scheme is aimed at increasing the number of donor organs.
It means incompatible friends and family of those in need can swap their kidneys to someone compatible.
Last year to 31 March, a record 829 living donors donated a kidney, compared to 690 on 2006/07 and 589 in 2005/2006.
Dr Paul Harden, from the Oxford Radcliffe Hospitals NHS Trust, said: "I think this is an additional opportunity and allows us to do more transplants than usually possible.
"Every year there is an increasing number of individuals on the kidney waiting lists.
"This is a real option for families to help one another."