What is a normal anion gap?

Many calculators use about 3-12 without potassium and about 8-16 with potassium, but the correct reference range depends on the local laboratory and formula.

Why correct anion gap for albumin?

Albumin is a major unmeasured anion. Low albumin can make the uncorrected anion gap look less elevated than the acid-base problem suggests.

When is delta ratio useful?

Delta ratio is mainly useful when the corrected gap is elevated and bicarbonate is low. It can suggest a mixed metabolic pattern, but it needs pH, blood gas and clinical interpretation.

Anion Gap Calculator

Calculate serum anion gap with optional potassium, albumin correction and delta ratio for cautious acid-base interpretation.

Na+, mmol/L

Cl-, mmol/L

HCO3-, mmol/L

K+, mmol/L

Include potassium in AG (reference 8-16)

Albumin, g/dL

If albumin is reported in g/L, divide the value by 10.

Medical limits

Anion gap helps classify metabolic acidosis patterns, but it does not diagnose acidosis by itself. Interpret the result with pH, pCO2, blood gas, lactate, ketones, creatinine, glucose, symptoms, and the clinical context.

Serum anion gap calculation

The anion gap is a calculated value from serum electrolytes used in acid-base review. English search results expect the standard Na, Cl and bicarbonate workflow, optional potassium and a clear note that the result must be interpreted with blood gas and clinical context.

AG = N a - (C l + H C O_{3})

Standard anion gap without potassium.

AG_{K} = (N a + K) - (C l + H C O_{3})

Alternative anion gap when potassium is included; use a separate reference interval.

Not a treatment decision

A high or low anion gap should be reviewed with pH, pCO2, bicarbonate, lactate, ketones, glucose, creatinine, albumin, medications, symptoms and the lab reference range.

Albumin correction and delta ratio

AG_{cor r ec t e d} = AG + 2.5 \times (4.0 - albumin_{g / d L})

Albumin correction commonly used when serum albumin is low.

Delta ratio = \frac{AG _{cor r ec t e d} - upper reference}{24 - H C O _{3}}

Only meaningful when the gap is elevated and bicarbonate is reduced.

Feature	Use carefully
Albumin correction	Low albumin can mask an elevated gap.
Potassium included	Compare with a potassium-included reference range.
Delta ratio	Screening clue for mixed metabolic disorders, not a diagnosis.
Blood gas	Needed for acid-base interpretation beyond the calculator.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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