The kidneys can have a direct influence on blood pH, by pushing hydrogen ions and bicarbonate into and out of urine.
Regulation of blood pH or acid-base homeostasis is maintained by kidneys. Kidneys regulate pH by excreting hydrogen ions (H⁺) into the urine and reabsorbing bicarbonate (HCO3⁻) from the urine. Acidosis (low blood pH) causes more bicarbonate to be reabsorbed and in response to alkalosis (high blood pH) kidneys excrete more bicarbonate.