What is the delta gap?

The delta gap is the difference between a patient's corrected anion gap and the normal anion gap (12 mEq/L). It represents how much the anion gap has risen above normal due to unmeasured anions.

What is the delta-delta ratio?

The delta-delta ratio divides the delta gap by the bicarbonate deficit (24 − actual HCO3). A ratio of 0.8–2.0 suggests a pure high-anion-gap metabolic acidosis. Values outside this range indicate a mixed disorder.

Why correct the anion gap for albumin?

Albumin is a negatively charged protein that makes up a significant portion of unmeasured anions. Each 1 g/dL drop in albumin below 4 g/dL lowers the anion gap by about 2.5 mEq/L, which can mask a true high-anion-gap acidosis.

What does a delta-delta ratio below 0.4 mean?

A ratio below 0.4 suggests that the bicarbonate is lower than expected from the anion gap elevation alone, indicating a concurrent normal-anion-gap (hyperchloremic) metabolic acidosis.

What does a delta-delta ratio above 2 mean?

A ratio above 2 means the bicarbonate is higher than expected, suggesting a superimposed metabolic alkalosis on top of the high-anion-gap metabolic acidosis.

What are normal reference values used here?

Normal anion gap = 12 mEq/L, normal bicarbonate = 24 mEq/L, normal albumin = 4.0 g/dL. These are the standard values used in most clinical delta gap calculations.

Delta Gap Calculator

Enter sodium, chloride, bicarbonate, and albumin to calculate the corrected anion gap, delta gap, and delta-delta ratio with clinical interpretation.

Lab Values

All values in mEq/L except albumin (g/dL).

Sodium (Na⁺) mEq/L

Normal: 136–145 mEq/L

Chloride (Cl⁻) mEq/L

Normal: 98–106 mEq/L

Bicarbonate (HCO₃⁻) mEq/L

Normal: 22–29 mEq/L

Albumin g/dL

Normal: 3.5–5.0 g/dL. Default 4.0 if omitted.

Enter lab values and click Calculate.

Results

Anion Gap

—

mEq/L (uncorrected)

Corrected AG

—

mEq/L (albumin-adjusted)

Delta Gap

—

Corrected AG − 12

Delta-Delta

—

Ratio

Interpretation

Delta-Delta Reference

Ratio	Interpretation
< 0.4	Pure NAGMA (normal-anion-gap metabolic acidosis)
0.4 – 0.8	Mixed HAGMA + NAGMA
0.8 – 2.0	Pure HAGMA (high-anion-gap metabolic acidosis)
> 2	Mixed HAGMA + metabolic alkalosis

HAGMA = high-anion-gap metabolic acidosis. NAGMA = normal-anion-gap metabolic acidosis. Normal AG = 12 mEq/L. Normal HCO3 = 24 mEq/L.

Clinical note: This calculator is a decision-support aid only. Clinical context, ABG findings, and patient history must guide management. Always verify results with your institution's reference ranges.

Summary

The delta gap calculator determines whether a patient with a high-anion-gap metabolic acidosis also has a concurrent normal-anion-gap acidosis or metabolic alkalosis — a finding that a simple anion gap alone cannot reveal. It corrects the anion gap for hypoalbuminemia and computes the delta-delta ratio with a clinical interpretation. Designed for clinicians, residents, and medical students working in emergency, ICU, or nephrology settings.

How it works

Enter the patient's serum sodium, chloride, and bicarbonate values in mEq/L.
Enter the serum albumin in g/dL (normal is 4.0 g/dL); the calculator corrects the anion gap for hypoalbuminemia.
The corrected anion gap (AG) is calculated: Na − Cl − HCO3, then adjusted for albumin: AG + 2.5 × (4 − albumin).
The delta gap is computed as: corrected AG − 12 (the expected normal AG).
The delta-delta ratio is: delta gap / (24 − HCO3), where 24 is the normal bicarbonate.
The ratio is interpreted: <0.4 = pure NAGMA, 0.4–0.8 = mixed HAGMA + NAGMA, 0.8–2.0 = pure HAGMA, >2 = mixed HAGMA + metabolic alkalosis.

Use cases

Identify a concurrent normal-anion-gap metabolic acidosis hiding behind a high-anion-gap acidosis.
Detect metabolic alkalosis superimposed on a high-anion-gap metabolic acidosis.
Evaluate acid-base status in diabetic ketoacidosis, lactic acidosis, or toxic ingestions.
Assist clinical decision-making in the ICU or emergency department.
Teach residents and medical students how to interpret complex acid-base disorders.
Cross-check arterial blood gas and basic metabolic panel results at the bedside.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu