Acid-base balance is precisely regulated by pulmonary and renal responses while body buffers help to control pH. When its regulation becomes abnormal, accumulation of hydrogen ions cause metabolic acidosis and several responses are activated. These responses interfere with the metabolism of bones and muscle. Metabolic acidosis induces abnormalities in the release and function of several hormones including defects in growth hormone, IGF-1, insulin, glucocorticoids, thyroid hormone, parathyroid hormone and vitamin D. Clinical consequences of these abnormal metabolic responses include impaired growth of infants and children and loss of bone and muscle mass in adults. Notably, abnormalities in bone and muscle metabolism can be present even when there is little or no decrease in the plasma bicarbonate concentration. The abnormalities can be corrected by treatment with NaHCO 3 . In patients with chronic kidney disease, many abnormalities in bone and muscle metabolism can be directly linked to the presence of metabolic acidosis and these abnormalities can be largely corrected by treating acidosis with NaHCO3. Recent insights indicate that several consequences of metabolic acidosis including the development of insulin resistance can stimulate muscle protein degradation by activating proteolytic mechanisms. To avoid abnormalities in metabolism and the loss of bone and muscle, metabolic acidosis must be corrected in normal adults and in patients with kidney disease.