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That’s 600 cups’ worth, passing through these two bean-shaped organs—every. Single. Day. Each kidney is about the size of your fist and made up of a million or so little filtering units called nephrons. Their job: to remove waste and excess fluid from your blood to produce urine. Urine flows from the kidneys to your bladder, en route to its exit. You pee out about one to two quarts of urine per day.
Your kidneys are responsible for helping balance your body’s sodium, potassium, and acid content. They also release hormones that regulate blood pressure, produce an active form of vitamin D that helps bones stay strong, and control the production of red blood cells.
That’s because too much glucose in your blood can damage your kidney’s blood vessels, breaking down their filtering system and resulting in a buildup of waste and excess fluid. Damaged filters also allow the protein albumin to pass out of your blood and into your urine. Your body needs that protein to stay healthy; a well-working kidney keeps it in place. Diabetes is the leading cause of chronic kidney disease, or the gradual loss of kidney function. Learn more about diabetes and kidney health and other diabetes complications here.
Over time, uncontrolled high blood pressure can cause arteries around the kidneys to narrow, weaken, or harden. The nephrons that filter your blood then can’t get the oxygen and nutrients they need to do their job. Extra fluid in the blood vessels can blood pressure to increase even more, creating a dangerous cycle. As more arteries become blocked, the kidneys may eventually fail. Learn more about your blood pressure numbers (what’s healthy, what’s not) here.
You won’t get much warning when your kidneys are in trouble. That’s because they’re super adaptable organs and can compensate for loss of function. In fact, most people with kidney disease have no symptoms in the early stages. Once kidney disease has progressed, some signs may include: nausea or vomiting; fatigue or weakness; urine that’s foamy, pink, or dark; puffy eyes; or swollen hands, feet, or ankles. (Here’s more info on what your urine color says about your health.) The best way to find out if you have kidney disease is to get tested. If you have diabetes, high blood pressure, or other risk factors for kidney diease, your doctor will likely take regular urine and blood tests to keep tabs on how well your kidneys are working.
Kidney stones are hard deposits made of minerals and salts; they form when urine becomes concentrated, which allows minerals to crystallize and stick together. When the stone is the size of a grain of sand, it may pass through your urinary tract without you feeling a thing. Consider yourself lucky. Any larger, and you’ll feel them in a big way. Some stone grow to a pea size; others can reach golf ball-size proportions. (Aw-ful.) As these move through your kidneys, they can get stuck in your urinary tract, blocking the flow of urine and causing sharp pains in your side and back. The pain may come and go in waves, fluctuate in intensity, and radiate to your lower abdomen or groin. Other symptoms include nausea and vomiting, fever, or blood in your urine. Treatment for kidney stones depends on the size and cause. (And in case you’re wondering, the Guinness World Book Record for the biggest kidney stone measured in at 5.11 inches wide!)
It’s the number one thing you can do to help prevent kidney stones. The extra water helps dilute the substances in urine that lead to stones. Some research also suggests drinking more fluid may also help protect against chronic kidney disease. Aim for six to eight, eight-ounce glasses a day. (One caveat: People with end-stage kidney disease or kidney failure may need to do the opposite and restrict water intake.)
When your kidneys can no longer function up to task, a process called dialysis artificially removes waste and extra fluid from your blood to keep your body in balance. There are two types of dialysis: one form uses a machine to pump blood out, clean it and return it to your body; with the other type, your blood is cleaned inside your body. In some cases, dialysis may only be needed for a short time until your kidneys get better. But if you have chronic or end-stage kidney failure, you’ll need dialysis treatments indefinitely until you can get a kidney transplant.
If you need to have a kidney removed to treat cancer or another disease; if you decide to donate one of your kidneys to someone in need; if you’re born with just one—a single kidney can do the job of two. Most people with a solitary kidney lead healthy, normal lives.
A kidney transplant involves placing a healthy kidney from a donor inside your body to do the work your own organs can no longer do. But in most cases, the surgeon will leave your two kidneys in place. The donated kidney is actually placed into your lower abdomen, where it can more easily be connected to the vital blood vessels and bladder. You’ll need to take medications for the rest of your life to keep your body from rejecting the new organ.