The reason most hospitals suggest an age minimum of 18 for kidney donors isn't because a young kidney is too small. Studies have shown that a kidney from a 6-year-old is all right to transplant into an adult.
Instead, the main reason is that people under 18 are minors and can't legally give their “informed consent” proving that they agree to the procedure. Also, some genetic kidney diseases won't have started to cause symptoms yet in young children and teenagers, so it's hard to know if their kidneys may be affected by disease.
How Old Is Too Old?
There is no age limit for kidney donations. At many institutions, donors over the age of 60, 65, or even 70 are considered on a case-by-case basis.
Between 1998 and 2017, 2,337 people over the age of 70 donated kidneys, and researchers say the number of donors in this age group is on the rise. As of 2021, the oldest organ donor was 91 years old.
Surgeons will make their decisions for this older group based on a potential donor's health and how well their kidneys work. If you have high blood pressure, diabetes, or are overweight, you probably won't qualify to be a donor. Even if you don't have health complications, the surgeon who would operate on you would make the final decision on whether to allow you to donate a kidney.
Is There a Downside to a Kidney From an Older Donor?
When studies have compared older kidneys -- those from people over age 50 or even over age 70 -- to kidneys from younger donors, they've found some minor differences.
Kidneys from younger donors seem to work better over the long term. But people who get older kidneys are just as likely to be alive 5 years after a transplant as those that receive younger kidneys. Plus, the chances of complications from the procedure, and of organ rejection -- when someone's immune system attacks their new kidney -- are the same with kidneys from all age groups.
The takeaway from these studies is that kidneys from older donors can work, but younger people in need of a kidney may want to consider being matched with younger donors.