What is renal reserve?

Physiology: This is one more way to see how good a person's kidney function is, to decide for example whether they can be a donor. A person may be given a radioisotope and their ability to clear it measured before and after they take a protein meal. It's a test of the ability of the kidney to increase its filtration rate (as when stimulated by a protein load.) ask a nephrologist how useful it is.

Redundant function : Your kidneys have built in capacity to sustain harm and keep you alive; measurements of your kidney reserve are imprecise. If your reserve is gone you need dialysis, at least temporarily.