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Overview of your kidneys

An illustration showing blood going into your kidney, filtered blood coming out and wastes (urine) going to your bladder.Your kidneys are two bean-shaped organs about the size of your fist. Most people have two kidneys and they sit just below your rib cage, one on each side of your spine.

With two healthy kidneys, each performs 50% of the normal kidney function. But it's possible to lead a healthy and active life with only one functioning kidney. If you lose a kidney, the other one can enlarge and provide up to 75% of your normal kidney function.

Your kidneys' main functions are to:

How your kidneys work

Your blood supply circulates through your kidneys about 12 times every hour. Your kidneys filter your blood to remove waste and excess fluid, which they turn into urine (wee). Your kidneys process around 200 litres of blood every 24 hours.

Each of your kidneys is made up of about a million filtering units called nephrons. Each nephron has a filter (called the glomerulus) and a tubule. Each nephron filters a small amount of blood.

The nephrons work through a two-step process.

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Written by HealthInfo clinical advisers. Last reviewed July 2021.

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Understanding your kidney function results

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