Patient information from BMJ

Chronic kidney disease: what is it?

Last published:Apr 29, 2025

Chronic kidney disease (CKD) is a serious condition where the kidneys stop working properly. The risk of developing CKD increases as you get older and if you have certain conditions.

There is no cure for CKD, but there are treatments that can help slow the disease.

What is CKD?

CKD is a long-term condition where your kidneys stop working properly. It’s common, but it often goes undiagnosed until it reaches a more advanced stage.

Your kidneys are located just below your ribs near the middle of your back, with one on either side of your spine. They filter waste products and extra fluid out of your blood. This waste then leaves your body as urine.

But the kidneys also have other important jobs like:

• helping to control your blood pressure

• controlling the level of acid in your blood

• ‘activating’ Vitamin D which your bones need to stay healthy

• producing erythropoietin (EPO), which is a hormone that helps to produce red blood cells.

When you have CKD, your kidneys can no longer do these jobs properly. This leads to other problems such as:

• uraemia (a build up of the waste product, urea, that your kidneys normally filter out)

• pulmonary oedema (a build-up of fluid in the body)

• hypertension (high blood pressure)

• metabolic acidosis (high levels of acid in the blood)

• osteodystrophy (a bone disorder that happens because of low Vitamin D)

• anaemia.

CKD is divided into different categories or ‘stages’ depending on how severe it is.

What causes CKD?

The most common causes of CKD are diabetes and high blood pressure. Both of these conditions can cause damage to the kidneys over time, leading to CKD.

The risk of developing CKD also increases with age. This is because your kidneys naturally work less well as they get older. This makes them more sensitive to any damage too.

Other, less common causes include:

• conditions that block the flow of urine (like an enlarged prostate)

• polycystic kidney disease (an inherited condition that causes cysts in the kidneys)

• kidney problems that develop in the womb, and

• autoimmune diseases (such as lupus).

What are the symptoms of CKD?

Most people with CKD don’t have any symptoms. In fact, symptoms often don’t appear until there has been significant damage to the kidneys. This means CKD is usually diagnosed when it reaches a more advanced stage.

Usually, CKD is picked up after a blood or urine test is done for other reasons. These tests pick up problems in your kidneys. For example:

• a urine test might show high levels of blood or protein

• a blood test might show reduced kidney function.

If a test does pick up these problems, you will need repeat tests. This is because problems need to be present for at least 3 months for your doctor to diagnose you with CKD.

Symptoms aren’t common in the early stages of CKD, but they can include:

• tiredness

• nausea

• urinating more or less often than usual

• puffiness around your eyes or swelling in your limbs (this is called oedema)

• loss of appetite and weight loss

• skin and nail changes (e.g., itchy skin, dry and scaly skin, or changes to the colour of your nails)

• restless legs (this is where you get a strong urge to move your legs)

• foamy or cola-coloured urine.

Many of these symptoms can also be caused by other conditions. This can make it difficult to tell whether you have CKD by just looking at your symptoms.

People with CKD usually have smaller kidneys than normal. So your doctor will usually suggest an ultrasound of your kidneys to help with diagnosis too.

If it’s not clear what is causing your CKD, you may need extra tests to diagnose any underlying conditions. This is important, as treating the cause of CKD can help prevent more damage to your kidneys.

What happens next?

CKD is a serious long-term illness. Over time, damage to the kidneys usually gets worse and leads to end-stage kidney disease. This is the last stage of CKD where your kidneys no longer work well enough to meet your body’s needs. People with CKD and end-stage kidney disease are more likely to die early.

There is no cure for CKD as damage to the kidneys is irreversible. But diagnosing and treating it as early as possible can help to slow further damage. Early treatment will help you to live a healthier, longer life.

It’s important that any other conditions you have are also treated. For example, if your CKD is caused by diabetes or high blood pressure, your doctor will want to make sure these are under control.

More information on treatment for CKD is available in our patient information Chronic kidney disease: what are the treatment options?