Kidneys
Kidneys
Two fist-sized filters processing about 180 litres of blood a day.
Filter blood, regulate fluid balance, control blood pressure and electrolytes, and produce hormones governing red blood cell production and calcium absorption. They filter around 180 litres of fluid a day and return almost all of it, producing 1 to 2 litres of urine.
Where it is
Either side of the spine at the back, roughly at the level of the lowest ribs.
The numbers
- Mass each
- 120–170 g
- Nephrons per kidney
- about 1 million
- Fluid filtered daily
- ~180 litres
- Urine produced
- 1–2 litres
Worth knowing
Kidneys receive about 20% of the heart’s output despite being under half a per cent of body mass. The right kidney sits slightly lower than the left, pushed down by the liver above it.
Structural reference only — this is not medical advice, and individual variation in every figure here is substantial. Anything concerning your own health belongs with a clinician rather than a reference page.
Common questions
- What does the kidneys do?
- Filter blood, regulate fluid balance, control blood pressure and electrolytes, and produce hormones governing red blood cell production and calcium absorption.
- Kidneys — key numbers
- Mass each: 120–170 g. Nephrons per kidney: about 1 million. Fluid filtered daily: ~180 litres. Urine produced: 1–2 litres.
Related pages
- Heart A four-chambered pump, roughly fist-sized, beating about 100,000 times a day.
- Brain About 1.4 kg, using roughly 20% of the body’s energy at 2% of its mass.
- Liver The largest internal organ, around 1.5 kg, and the only one that regenerates.
- Lungs Two unequal lungs with a gas-exchange surface of about 70 square metres.
- Skin The largest organ — about 2 m² and 4 kg in an adult.
- Bones Bones
- Blood types Blood
- Teeth Teeth
- Blood Blood
- The senses Senses
- Taste Senses
Sources
- Typical range compiled from manufacturer specifications — At One Place