The concentration of anions and cations in plasma must be equal to maintain electrical neutrality. However, only ceain cations (Nat) and anions (C1-, HCO3- ) are routinely measured in clinical laboratory. Anion gap (AG) represents the unmeasured anions in the plasma. (difference between 'unmeasured cations & unmeasured anions') It is calculatedQ as follows: AG = The most impoant unmeasured cations: Ca2+, Mg2+, K+ The most impoant unmeasured anions: Proteins (Albumin), sulphate, phosphates Proteins are present in our body in much more quantities as compared to other unmeasured anions.">