The normal unremoved kidney compensates for the removed kidney. The GFR of the kidney increases by 25-40 % and the total GFR achieved in 4-6 weeks is about 80 % of the original GFR of the two kidneys. A person with one normal kidney can perform & live like any other normal person with two kidneys. One in 5000 people are born with one kidney only and many times may not know that they have one kidney.