Check compensation : Use Winter’s formula for metabolic acidosis; appropriate rules for metabolic alkalosis or respiratory disorders (acute vs. chronic)
Calculate Anion Gap (AG) : AG = Na⁺ − (Cl⁻ + HCO₃⁻).
Correct for albumin : AGcorr = AG + 2.5 × (4 − Alb).
Elevated AG suggests unmeasured anions (lactate, ketones, toxins)