The Body

Grown-ups

Kidneys

Your two kidneys clean your blood and turn extra water and waste into pee.

Red blood comes into the kidney to be cleaned and leaves through the blue vein. The waste and extra water drip down to the bladder as pee. Tap any part!

Two beans by your back

You have two kidneys. Each one is shaped like a bean and is about the size of your fist. Kidney beans are named after kidneys, not the other way around!

They sit toward your back, one on each side of your spine, just above your waist. Your lowest ribs help protect them.

Try it: put your hands on your hips, then slide them up until you feel your lowest ribs. Your kidneys are tucked deep inside, toward your back, about there.

Blood cleaners

Your blood picks up waste as it travels around your body. If the waste stayed, it would make you sick, so your kidneys clean it out.

All your blood passes through your kidneys many times a day. In a grown-up, the kidneys filter about 150 quarts of blood every day. That's almost a whole bathtub!

Each kidney has about a million tiny filters called nephrons (NEF-rons). Each one works like a little strainer, keeping the good stuff and letting waste and extra water through.

Making pee

The waste and extra water become urine (YUR-in), better known as pee. Your kidneys filter lots of blood, but only about 1 to 2 quarts of pee are made each day in a grown-up. The rest of the water goes back into your blood.

Pee leaves each kidney through a thin tube called a ureter (yoo-REE-ter). The two ureters carry it down to your bladder, where it waits until you go.

Pee is yellow because of a leftover from old red blood cells. Pale yellow pee usually means you're drinking enough water. Dark yellow pee can mean your body needs more.

Balance keepers

Your kidneys are smart water managers. If you drink a lot, they make more pee. If you're thirsty or sweaty, they save water and make less.

They also keep just the right amount of salt and other minerals in your blood.

And they make hormones that help your bone marrow make red blood cells and help keep your bones strong.

Living with one kidney

Most people have two kidneys, but one healthy kidney can do the work of two. Some people are born with just one.

Some grown-ups even give one of their kidneys to a person who needs it. That's a very kind gift, and both people can live healthy lives.

🤩 Wow facts

  • Kidney beans are named after kidneys, because they're the same shape.
  • A grown-up's kidneys clean about 150 quarts of blood a day.
  • Each kidney has about a million tiny filters.
  • One healthy kidney can do the job of two.
  • Your kidneys help make a hormone that tells your bone marrow to make red blood cells.
  • Your kidneys make less pee at night, so you can sleep.

💚 Look after it

  • Drink water through the day, and more when it's hot or you're playing hard.
  • Go to the bathroom when you need to.
  • Eat fruits and vegetables, and go easy on very salty snacks.
  • Only take medicine when a grown-up gives it to you.

🩹 When something goes wrong

Kidney stones. Sometimes minerals in pee clump into tiny hard bits called kidney stones. They're more common in grown-ups and can hurt. Drinking water helps keep them away. If your side or back hurts a lot, tell a grown-up so a doctor can help.

🙋 Questions kids ask

Why is pee yellow?

It carries a yellow leftover from old red blood cells. More water makes pee paler, and less water makes it darker.

Can you live with one kidney?

Yes. One healthy kidney can do the work of two.

Why do I pee more when I drink a lot?

Your kidneys keep just the right amount of water in your body. The extra water goes out as pee.

🧠 Quick quiz

Question 1 of 3What are kidneys shaped like?

🔗 It works with

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