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5-minute read

What are kidneys?

The kidneys are organs that sit at the back of your abdomen (tummy). They are found below your ribs on either side of your spine.

The kidneys are shaped like a bean and are about the size of your fist. Each kidney weighs about 150 grams.

Most people are born with 2 kidneys. The right kidney is often a little lower than the left.

What do kidneys do?

Kidneys are very important to your overall health. Your kidneys have 3 main roles.

1. Filtering blood

Your kidneys filter your blood, removing waste products that are then removed from your body in urine (wee).

2. Balancing fluids

Your kidneys balance the fluids and electrolytes in your body. Electrolytes are minerals, like sodium, calcium, and potassium, that have a key role in how your body functions.

3. Making hormones

Your kidneys produce hormones that are involved in:

The kidneys are part of your urinary system

The kidneys are part of the urinary system, which also includes:

  • ureters (tubes connecting the kidneys to the bladder)
  • bladder (for storing urine)
  • urethra (the tube connecting your bladder to the outside of your body, so that you can urinate (wee))

Blood travels to the kidneys through the renal arteries. It then passes through millions of tiny filters called nephrons, before leaving your kidneys via the renal veins.

an anatomy diagram showing kidneys and their placement within the ribcage
An anatomy diagram showing kidneys and their placement within the ribcage.

Healthy kidneys

It’s important to keep your kidneys healthy, so that they can perform their role well. If your kidneys aren’t healthy, it can affect other organs in your body.

Things you can do to keep your kidneys healthy:

Kidney disease

It is difficult to know when your kidneys aren’t working well. You can lose up to 90% of your kidney function before you have any symptoms.

You should be aware of the risk factors that lead to kidney disease.

Kidney disease can lead to kidney failure, possibly requiring dialysis or a transplant.

Most kidney damage occurs gradually, over several years. If found early, changes to your lifestyle, diet and medicines may prevent further damage. Diagnosing kidney disease early is very important. You are at much higher risk of heart problems if you have kidney disease.

Your doctor might order blood and urine tests if you have diabetes, high blood pressure or heart disease. These tests are used to check your kidney function.

ARE YOU AT RISK? — Are you at risk of type 2 diabetes, heart disease or kidney disease? Use our Risk Checker to find out.

CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.

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Last reviewed: June 2022

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