How Well Do You Know Your Kidneys?

Your kidneys have a lot of work to do. They remove waste and extra fluids from your body. They also keep your salt and potassium levels in check. And they produce hormones that make red blood cells and help keep your blood pressure under control.

Most people have two of these bean-shaped organs. They're located at the bottom of your rib cage on either side of your spine.

Your kidneys sift through enough blood to fill a large bathtub each day. After your body takes what it needs, they turn the waste and extra water into pee -- about 2 quarts a day.

Early on, people with kidney disease usually don't have symptoms. But as things get worse, a change in bathroom habits -- having to go more or less -- can signal a problem. You may also feel tired, have muscle cramps, lose your appetite, and have swollen hands or feet and dry, itchy skin.

When they can’t filter anymore, your body fills up with wastes, fluids, and toxins. You either need a new kidney or have to go on dialysis.  That’s when a machine acts as an artificial kidney, cleaning your blood. You may need it done daily or a few times a week.

High blood pressure can hurt small blood vessels in your kidneys. That makes it harder for them to do their job. If you have diabetes, too much blood sugar can harm them. Some blood pressure drugs -- specifically, ACE inhibitors or ARBs -- can help protect them from diseases.

Thousands of people donate kidneys each year and stay healthy afterward. In fact, it's the No. 1 most common organ donated in the world. You can give one to a friend, family member, or even a stranger.

Some people are born with one kidney. If one is missing, damaged, or removed, your other one can grow larger to become nearly the size of two kidneys. That helps it do the job of both.

Living donors are healthy people who have chosen to give away a kidney to help someone. This may be a relative or friend, or it may be a stranger. People can also sign up to be donors so their kidneys can be used after their death. If their wishes aren’t known, family members can donate their loved ones' kidneys.

By the time you finish this quiz, someone has been added to the national kidney transplant waiting list. More people wait for a kidney than all other organs, including the heart and liver, combined. The latest stats show more than 100,000 people are now on the kidney transplant waiting list. It can be a long wait because supply is low. On average, it takes about 3.6 years to get a new kidney.

If you don’t drink enough water or other fluids, you’ll get dehydrated. That can damage your kidneys and cause kidney stones. Take a look when you go to the bathroom: Is your pee clear to light yellow? It should be if you're drinking enough.

It might feel that way if you get one, but they can be as tiny as a grain of sand or as big as a pearl -- or a golf ball, but that's rare. They form when there's too much of a certain substance, like calcium, in your urine. They can stay in your kidney or travel down the urinary tract, where pee leaves your body. You’re more likely to get them if other people in your family have had them.

Because these organs are a filter, too much of anything in your bloodstream can be bad. Some pain medicines -- like ibuprofen and naproxen -- can damage them, especially if you take too much, too often. Don't take more than the recommended dose on the label. Drink plenty of water. And talk to your doctor if you use the drugs more than once in a while.