What do the kidneys do?

The kidneys perform several functions:

maintaining the salt and water balance by regulating the plasma concentration of electrolytes (sodium, potassium, chlorine, calcium, magnesium and phosphates) and eliminating excess fluid through the urine

regulating the acid-base equilibrium (blood pH control) through the reabsorption of bicarbonates and the excretion of hydrogen ions

eliminating the terminal products of metabolism (urea, uric acid, creatinine etc.) and foreign substances (pharmaceutical drugs)

producing hormones, including erythropoietin, which stimulates the formation of red blood cells, and renin, which regulates blood pressure

regulating calcium metabolism, which is crucial for our bones, by activating vitamin D.