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The basics

This section describes the kidneys and how they work, and then explores what can go wrong to cause kidney disease.

Although many people develop kidney disease for no known reason, there are certain conditions (eg, diabetes and high blood pressure) which increase the likelihood of kidney problems. It is particularly important that people with these conditions are aware of the symptoms of kidney disease, as this will help ensure early diagnosis and treatment.

What and where are the kidneys?

The kidneys are bean-shaped organs about the size of a fist. They are located at the bottom of the rib cage at the back of the body.

What do the kidneys do?

  • Remove waste products (from metabolism of the food we eat and body cells).
  • Remove excess fluid to balance fluid levels in the body.

In addition to filtering the blood, the kidneys also:

  • Help control blood pressure
  • Produce hormones and chemicals which Help production of red blood cells
  • Maintain healthy bone

How do the kidneys work?

The kidneys act like sieves, filtering the waste and excess fluid from the blood. Blood passes through the kidneys and is cleaned before returning to the heart.

  1. First blood enters the kidneys via the renal arteries.
  2. Then, inside the kidneys, millions of mini-filtering systems called nephrons sieve the blood.
  3. Certain substances the body needs are reabsorbed and the waste products and extra fluid that the body does not need are removed in the form of urine.
  4. The clean blood returns to the body through the renal veins.
  5. The urine is carried from the kidneys to the bladder by tubes called ureters.
  6. The bladder stores the urine until it is full, when the urine passes out of the body via the urethra.

Each day, the kidneys process about 190 litres (335 pints) of blood through 145 miles (225km) of ‘tubes’ and millions of mini filtering systems called ‘nephrons’.in addition to filtering the blood and balancing fluid levels in the body, the kidneys also produce different hormones and chemicals, which perform several key functions.

Erythropoietin is a hormone which travels in the bloodstream from the kidneys to the bone marrow where it prompts the bone marrow to make red blood cells. Red blood cells carry the oxygen the body needs to function properly. Without healthy red blood cells, people develop anaemia, which can cause them to feel weak, cold, tired and short of breath.

Control of blood pressure – when kidneys are diseased, blood pressure increases. High blood pressure is important - it can increase the risk of stroke, heart disease and further damage the kidneys.

The kidneys maintain the correct balance between calcium and phosphate in the blood and the bones, and produce vitamin D. So when the kidneys fail, there can be problems with the bones.

How to improve your kidney health

Monitor your blood pressure - High blood pressure accelerates kidney damage. To protect yourself from kidney disease you should also maintain a diet low in salt and saturated fats.

Keep fit and active - This helps reduce your blood pressure and therefore reduces the risk of kidney disease.

Don’t smoke - Smoking slows blood flow to the kidneys, deceasing their ability to function properly.

Eat healthily and keep your weight in check - This can help prevent diabetes, heart disease and other conditions associated with kidney disease.

Get your kidney function checked - If anyone in your family has suffered from kidney disease, you are diabetic or have high blood pressure or if you are of South Asian or African-Caribbean ethnic background.

Keep well hydrated - This helps the kidneys clear sodium, urea and toxins from the body which can significantly lower risk of developing chronic kidney disease*.

*Dialysis patients need to restrict their fluid intake.

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The National Kidney Federation cannot accept responsibility for information provided. The above is for guidance only. Patients are advised to seek further information from their own doctor.