How can someone live with only one kidney?
A single kidney is able to meet the body’s needs very well. In fact, about 1 of every 750 perfectly healthy people is born with only one kidney. We are born with approximately 4—5 times the kidney function we need for good health. So a person who donates a kidney still has 2-3 times the amount of functioning he or she needs to live a normal, healthy life.4 The remaining kidney continues to function normally and compensates well for the loss of the donated kidney.
4 Dr. Del Pizzo: Kidney Donation: Living with One Kidney