Advanced Anion Gap Calculator

Enter Laboratory Values

Use electrolyte values in mEq/L and albumin in g/dL. The calculator supports classic anion gap, potassium-inclusive gap, albumin correction, and delta ratio review.

Patient Label

Sodium (mEq/L)

Chloride (mEq/L)

Bicarbonate (HCO₃⁻) (mEq/L)

Potassium (mEq/L)

Albumin (g/dL)

Normal Anion Gap Reference

Normal Bicarbonate Reference

Reference Albumin

Optional Potassium Method

Include potassium in the anion gap equation

Clinical Notes

Formula Used

Primary Formula

Standard anion gap:

Anion Gap = Sodium − (Chloride + Bicarbonate)

Potassium-inclusive option:

Anion Gap = (Sodium + Potassium) − (Chloride + Bicarbonate)

Advanced Calculations

Albumin-corrected gap:

Corrected Gap = Anion Gap + 2.5 × (Reference Albumin − Measured Albumin)

Delta ratio:

Delta Ratio = (Effective Gap − Normal Gap) ÷ (Normal Bicarbonate − Measured Bicarbonate)

The effective gap is the corrected gap when albumin is entered. Otherwise, the measured anion gap is used for delta calculations.

How to Use This Calculator

Enter sodium, chloride, and bicarbonate from the chemistry panel.
Add potassium if you want the potassium-inclusive method.
Enter albumin to calculate an albumin-corrected anion gap.
Adjust normal reference values if your lab uses different targets.
Click the calculate button to show the result above the form.
Review the interpretation, graph, and supporting metrics.
Use the CSV or PDF buttons to save the report.
Interpret results with symptoms, blood gas data, and clinical judgment.

Example Data Table

Scenario	Na	K	Cl	HCO₃⁻	Albumin	Anion Gap	Corrected Gap	Interpretation
Reference Chemistry	140	4.0	104	24	4.0	12	12	Expected range
Lactic Acidosis Pattern	140	4.5	100	12	4.0	28	28	High-gap pattern
Hypoalbuminemia Example	138	4.0	106	20	2.0	12	17	Hidden elevation after correction

Frequently Asked Questions

1) What does the anion gap estimate?

It estimates unmeasured ions in serum by comparing major measured cations and anions. It is commonly used during acid-base evaluation.

2) Why would I include potassium?

Some labs and textbooks use a potassium-inclusive equation. Others omit potassium because its concentration is relatively small. This calculator supports both methods.

3) Why does albumin matter?

Albumin is a major unmeasured anion. Low albumin can lower the measured anion gap and hide clinically important elevations unless correction is applied.

4) What does a high anion gap suggest?

It can support high anion gap metabolic acidosis, which may occur with lactate elevation, ketoacidosis, renal failure, toxins, or mixed disorders.

5) What is the delta ratio used for?

Delta ratio helps screen for mixed metabolic disorders by comparing the gap rise with the bicarbonate fall. It is a guide, not a standalone diagnosis.

6) Can a normal anion gap still be important?

Yes. A normal measured gap does not exclude disease. Hypoalbuminemia, timing, treatment, and mixed disorders can change the apparent result.

7) Should I use lab-specific reference values?

Yes. Different analyzers and local practices can shift normal ranges. Use your lab’s reference interval when available for the best bedside interpretation.

8) Is this calculator enough for diagnosis?

No. It is an educational decision-support tool. Confirm findings with the clinical picture, medication history, blood gas results, and full metabolic panel.

Clinical Note

This tool supports structured acid-base review, but it does not replace physician assessment, laboratory verification, or emergency evaluation when severe illness is suspected.