What function do the kidneys perform?

The kidneys are small organs that filter and remove waste from your blood. Our kidneys also maintain salt/water balance and regulate other chemicals. Learn more about kidney function in this video from the National Kidney Foundation.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

The two kidneys that flank the lower spine are exemplary organs. They are multitasking machines charged with controlling the body's fluid balance, filtering the blood of waste and producing a host of regulating hormones. They are not only at the center of the urinary system, but they also have a hand in making red blood cells and vitamin D. When they fail, the breakdown can have body-wide ramifications.

The function of a kidney is to filter blood through our body and rid the body of any toxins. 

Kidneys play several important roles in your body, including regulating blood pressure and fluids in your body, producing hormones that help in the production of vitamin D and red blood cells and even removing drugs, toxins and waste products from your blood.

Dr. Jeanne Morrison, PhD
Family Practitioner

You have two kidneys and they are located on either side of the spine at the lower level of your rib cage. Even though they are only the size of a fist they do a lot of work each day. Each kidney has over a million functioning units called nephrons and within each nephron is tiny filtering units called the glomerulus. Your blood passes through this filtering unit and the remaining fluid is then passed along a tubule. When the blood reaches the tubule, chemicals and water are added or removed from this filtered fluid . . . according to what your body needs. The final product is urine.


The kidneys' main function is to clean the blood. They also make hormones, and decide which substances to keep in the body, and which ones to get rid of.

Dr. Jill Rabin
OBGYN (Obstetrician & Gynecologist)

The kidneys constantly filter the body’s blood supply by separating and eliminating toxins and waste products from those things that the body needs, such as certain nutrients.

Urine is a combination of about 5 percent of these dissolved waste products (urea, uric acid and creatinine) and about 95 percent excess water. The kidneys adjust the composition of urine in order to maintain water balance, electrolyte concentrations, the secretion of certain hormones and the activation of vitamin D.

Most people have two bean-shaped kidneys, which are located in the back on either side of the spinal cord and which are protected by the rib cage and by a layer of fat.

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Your kidneys are a pair of organs located on either side of your spine, just below your rib cage, that are crucial to the normal functioning of your body. About the size of small soup cans, the kidneys perform the complicated task of filtering metabolic waste and excess liquid from blood and optimizing the composition of blood with protein and fresh blood cells. To discard the waste and excess fluid, the kidneys create urine, which is then transported via the ureters to the bladder where it is stored until the bladder is full and needs to empty the urine out the urethra.

This filtering process also helps your body to maintain proper levels of electrolytes (such as sodium and potassium) and hormones that can help your body maintain a healthy blood pressure, make red blood cells and keep your bones strong.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.