Metabolic acid-base disorders frequently occur in emergency and critically ill patients. Recognizing these disturbances can be challenging, particularly when multiple acid-base imbalances coexist within a single patient. The anion gap (AG) and strong ion gap (SIG) are valuable calculations that help identify complex metabolic acid-base disturbances associated with unmeasured anions. This review provides definitions, reference values, indications, limitations, and guidelines for interpreting AG and SIG changes in clinical settings.