What do the kidneys do?
The kidneys filter waste and extra water from the blood to make urine. They also balance salts, control blood pressure and help make red blood cells.
Most people have two kidneys, each about the size of a fist, below the ribs on either side of the spine. Together they filter about 180 liters of blood fluid a day, returning most of it to the blood and producing about 1 to 2 liters of urine.
Each kidney contains about a million tiny filters called nephrons. Besides removing waste, the kidneys release hormones: renin helps control blood pressure, erythropoietin signals the bone marrow to make red blood cells and an active form of vitamin D helps keep bones strong.
Living with one kidney
A person can live a healthy life with just one working kidney, which is why living kidney donation is possible. When both kidneys fail, people need dialysis or a kidney transplant.
Did You Know?
High blood pressure and diabetes are the leading causes of kidney disease, so controlling them helps protect the kidneys.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.