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Anion Gap Calculator

Anion gap calculator determines the difference between measured cations and anions in serum. Normal anion gap is 8 to 12 mEq/L, and elevated values help identify causes of metabolic acidosis such as DKA, lactic acidosis, and toxic ingestions.

Enter Values

Sodium (Na+) mEq/L

Chloride (Cl-) mEq/L

Bicarbonate (HCO3-) mEq/L

Potassium (K+) mEq/L

Result

Enter values above and click Calculate to see your result.

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Formula

Core Formula

\text{AG} = \text{Na}^+ - (\text{Cl}^- + \text{HCO}_3^-)

How it works: Measures the difference between measured cations and anions in the blood.

Worked Example

Sodium 140, Chloride 104, Bicarbonate 24 -> Anion Gap 12.

Understanding the Anion Gap

The anion gap is a calculated value used to identify the cause of metabolic acidosis. It represents the "unmeasured anions" in the serum.

Standard formula: AG = Na - (Cl + HCO3), normal range 8 to 12 mEq/L
High Anion Gap Metabolic Acidosis (HAGMA) suggests MUDPILES causes: Methanol, Uremia, DKA, Propylene glycol, Isoniazid, Lactic acidosis, Ethylene glycol, Salicylates
Low albumin falsely lowers the AG by about 2.5 mEq/L for every 1 g/dL albumin drop below 4.0
Non-anion gap (normal AG) acidosis is often caused by diarrhea, renal tubular acidosis, or saline infusion
The delta-delta ratio compares the rise in AG to the fall in HCO3 to detect mixed acid-base disorders

This calculator is for educational purposes only. The anion gap must be interpreted alongside clinical presentation, arterial blood gas, and other laboratory values.

You can also calculate changes using our Corrected Calcium Calculator or Creatinine Clearance (CrCl) Calculator.

Frequently Asked Questions

What is a normal anion gap range?

A common reference range is 8 to 12 mEq/L without potassium, or 12 to 16 mEq/L if potassium is included. Ranges may vary by laboratory.

What does a high anion gap mean?

A high anion gap usually indicates metabolic acidosis caused by unmeasured acids, such as in diabetic ketoacidosis (DKA), lactic acidosis, renal failure (uremia), or toxic ingestions like methanol or ethylene glycol.

Should I include potassium in the calculation?

Most clinical practices use the formula without potassium. If you include it, the normal range shifts higher (typically 12 to 16 mEq/L).

What does MUDPILES stand for?

MUDPILES is a mnemonic for causes of high anion gap metabolic acidosis: Methanol, Uremia, Diabetic ketoacidosis, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, and Salicylates.

How does albumin affect the anion gap?

Albumin is an unmeasured anion. For every 1 g/dL drop in albumin below 4.0, the expected normal anion gap decreases by about 2.5 mEq/L, which can mask a true high anion gap acidosis.

Is this calculator a substitute for medical advice?

No. This tool is for educational purposes only. Always consult a qualified healthcare professional for diagnosis and treatment of acid-base disorders.

How do I add this Anion Gap Calculator to my site?

Absolutely. Use the "Embed" option above to tailor the dimensions, color scheme, and styling to match your site. Copy the generated iframe snippet and drop it into your HTML, WordPress editor, or any CMS. There is no cost and no account required. See calculory.com/services/embed-calculators for a step-by-step walkthrough.

Medical Disclaimer

This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.

AI Assistant

Ask about this calculator

I can help you understand the anion gap calculator formula, interpret your results, and answer follow-up questions.

Try asking

Our AI assistant provides general estimates and advice only. Please consult a qualified healthcare professional before making any health-related decisions.

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Corrected Calcium Calculator Creatinine Clearance (CrCl) Calculator

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