Normal human plasma PH value is 7.35~7.45. Normal human plasma PH value fluctuates between 7.35~7.45, which is the key to ensure the normal function of blood, plasma PH value less than 7.35 suggests acidosis, plasma PH value greater than 7.45 suggests alkalosis. Plasma PH value is influenced by two major factors such as body metabolism and respiratory function. There are acid-base buffer pairs in the blood, and the buffer pairs that play an important role are NaHCO₃/H₂CO₃, protein sodium salt/protein, and Na₂HPO₄/NaH₂PO₄; these buffer pairs act as regulators of the blood, thus maintaining plasma pH within the normal range of values. Plasma pH is usually measured by arterial blood gas analysis of arterial blood.