The kidneys are organs that sit in your abdomen, low down at the back. Their main function is to filter or 'clean' your blood of waste products. Kidneys are so important that we have two of them - a spare if one stops working.
Kidneys are part of the urinary system, which also includes:
- ureters (tubes connecting the kidneys to the bladder)
- bladder (for storing urine)
- urethra (tube connecting your bladder to the surface of the body, for urination).
Almost everyone is born with two kidneys. They are shaped like a bean and are about the size of your fist and each kidney weighs about 150 grams.
They sit on each side of your backbone, between your ribcage - which partially protects your kidneys - and the lower back. In most people, the right kidney is a little lower than the left.
Blood travels to the kidneys through the renal arteries, and leaves through the renal veins.
What do kidneys do?
Kidneys are very important to your overall health.
Nutrients from what you eat and drink enter the blood, and nourish the cells in your body. Waste products from this process need to be removed. Kidneys filter these waste products from the blood.
The waste combines with excess water and leaves your bladder through the urethra as urine.
Your kidneys also help:
- control blood pressure
- make red blood cells
- keep bones strong and healthy
- control the levels of chemicals and salts (electrolytes) in your blood.
Most kidney damage occurs gradually, over several years.
If detected early, lifestyle or dietary changes and medications may prevent further damage.
To keep your kidneys healthy:
- don't smoke
- keep your cholesterol within healthy limits
- maintain a healthy diet, weight and lifestyle
- exercise regularly (this reduces your risk of heart disease and high blood pressure, both risk factors for kidney disease)
- drink plenty of water.
People with diabetes should keep blood glucose within recommended levels.
Last reviewed: August 2015