Serum Anion Gap
AG = Na − (Cl + HCO₃⁻). Values are teaching bands only.
Calculator
How it works
The serum anion gap estimates unmeasured anions versus unmeasured cations from routine electrolytes. It is a bedside teaching construct and laboratory reference intervals vary.
Limits
Does not replace delta-delta, osmolar gap, ketone/lactate testing, or toxicology; low albumin lowers the expected gap; some analyzers use ion-selective electrodes affecting “hyperchloremic” patterns.
Educational tool only—not for diagnosis or treatment decisions.