Kidneys
Key facts
- Kidneys are organs that filter your blood, remove waste through urine and control your blood pressure.
- They are protected by fat and muscles and connected to the bladder through tubes.
- Blood flows into the kidneys, is filtered clean and exits from the body as urine.
- Kidney problems such as chronic kidney disease usually develop slowly.
- Managing risk factors such as diabetes and high blood pressure can help prevent kidney problems.
What are kidneys?
Kidneys are bean-shaped organs about the size of your fist. Most people have 2 kidneys. They act like a special filter system for your body.
Your kidneys remove waste from your blood and produce urine. They also help control the levels of many substances in your blood and manage your blood pressure.
What is the function of the kidneys?
Your kidneys are important to keep your body healthy. They work nonstop to clean your blood and get rid of waste. Here’s what they do:
- filter blood — by removing toxins and waste products
- make urine — they turn waste and extra fluids into urine, which your body then gets rid of when you urinate (wee)
- control blood pressure — by controlling the amount of fluid and salt in your blood they help keep your blood pressure at the right level
- produce vitamin D — which is important for healthy bones and for making red blood cells
Making hormones
Your kidneys also produce hormones that help:
- control your blood pressure and blood flow
- balance minerals such as sodium and potassium in your body
- manage how much water your kidneys keep which affects how concentrated your urine is
What are the different parts of the kidneys?
Kidneys are made up of basic working units called nephrons. Each kidney has about a million nephrons. Each nephron has two main parts:
- glomerulus — a tiny ball-like cluster of blood vessels that filters your blood
- tubule — a long and twisted tube that reabsorbs needed substances and sends waste to be turned into urine
Your kidneys are in the middle of your back, one on each side of your spine. They are protected by:
- a layer of fat
- lower ribs
- back muscles
The urinary system
The kidneys are part of the urinary system. Parts of this system include the following:
- 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 you can urinate (wee)
How do the kidneys work?
Blood comes into your kidneys through big tubes called renal arteries. Once inside it goes through tiny filters called nephrons. These filters clean the blood by getting rid of waste.
Inside the nephrons is a structure called the glomerulus, which filters the blood. The clean blood leaves the kidneys through the renal vein. Waste and extra water stay behind.
The waste and extra water turn into urine. This flows into small tubes called tubules. The urine moves to larger tubes called ureters.
The ureters carry urine from the kidneys to the bladder where it's stored. When you need to urinate (wee), the urine leaves the bladder through a tube called the urethra and exits your body.
What medical conditions are related to the kidneys?
Most kidney problems develop slowly. There are several medical conditions related to the kidneys, such as:
Most people have 2 kidneys. Some people are born with just one kidney. One kidney can still work well enough for most people most of the time. If you know you only have one kidney, ask your doctor to advise you on the best way protect it, so you can continue to live well.
Chronic kidney disease
Chronic kidney disease often doesn’t show symptoms until its quite severe. You can lose up to 90% of your kidney function before you notice anything.
Diagnosing chronic kidney disease early is important. It often gets worse when you have risk factors, which can lead to kidney failure. People with kidney failure may need dialysis or a kidney transplant.
Risk factors
Kidney disease can often be prevented by managing risk factors such as:
Managing your risk factors can help slow down kidney disease and prevent it from getting worse.
Your doctor or urologist might order blood and urine tests to check your kidney function.
CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.
How can I take care of my kidneys?
It’s important to keep your kidneys healthy so that they can perform their role well.
Things you can do to keep your kidneys healthy include:
- monitor your blood sugar levels if you have diabetes
- regularly check your blood pressure and keep it within the recommended range
- aim to regulate your weight if you are living with obesity
- stay hydrated by drinking plenty of water
- eat a healthy diet that includes a variety of fruit, vegetables, legumes, whole grains and dairy
- exercise regularly to lower your risk of heart disease and high blood pressure
- limit your intake of alcohol and don't smoke
Resources and support
Visit Kidney Health Australia for more information on kidney health for you or your child.
You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.
Other languages
Kidney Health Australia has translated information on the risks of kidney disease and how to manage your kidney disease.
Learn more here about the development and quality assurance of healthdirect content.
Last reviewed: June 2024
