HCO3- The reference range for normal adults is 22-28 mmol/L and for normal children is 21-25 mmol/L. HCO3- generally refers to the value of bicarbonate content in the human body. The actual level of bicarbonate in blood and plasma is measured by blood gas acid-base analyzer in a completely air-isolated testing environment, and this index can be used clinically to assist in diagnosing the state of acid-base metabolic balance of human body fluids. If the actual value of HCO3- is higher than the highest reference limit, the presence of respiratory alkalosis is initially considered, and if not, the presence of respiratory acidosis is considered. However, the diagnosis of the specific disease needs to be based on the actual symptoms of the patient and a more detailed special examination in order to develop a targeted treatment plan.