What do your kidneys do?

Your kidneys are vital for your survival. Their main functions are filtering waste from your blood and balancing levels of salts, minerals and water, which in turn help to regulate your blood pressure. They are also involved in activating vitamin D to a form that your body can use to absorb calcium from food, thus keeping your bones strong, and in the production of red blood cells.

Where are your kidneys?

Your kidneys are on either side of your spine, below your ribcage and behind your belly. If you put your hands around your hips and then slide them upwards until you can feel your ribs with your fingers, your kidneys are at the back, under your thumbs. You cannot feel them, but they are there, well embedded in your body. Most people have two kidneys, but you can live normally with only one. This is why it is possible to donate one for transplant into someone else. Your kidneys are bean-shaped and roughly fist-sized.

How do your kidneys work?

Depending on your weight, you will have about 4.5-6.5 litres of blood constantly circulating around your body. When your body has taken the nutrition it needs from your food and drink, some waste products go back into your blood. The renal arteries carry this blood into your kidneys, where it is filtered through about one million microscopically small nephrons. Your blood then leaves your kidneys through the renal veins, while waste and excess water that have been filtered out leave the kidneys through the ureters, as urine, are collected in the bladder and excreted through the urethra.

About 1,500 litres of blood pass through your kidneys every day. Most kidney diseases occur when the nephrons lose their ability to filter and dangerous levels of fluid and waste products can build up.


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