Anion Gap Calculator

The Anion Gap Calculator estimates the anion gap based on serum sodium, chloride, and bicarbonate levels. This tool helps clinicians and medical professionals quickly evaluate acid-base disorders and determine the cause of metabolic acidosis. Whether diagnosing high anion gap acidosis, monitoring treatment response, or analyzing complex lab results, this calculator provides immediate data for critical clinical decisions.

Enter sodium level in mEq/L or mmol/L
Enter chloride level in mEq/L or mmol/L
Enter bicarbonate level in mEq/L or mmol/L

How Anion Gap Is Calculated

The anion gap represents the difference between measured cations and anions in your blood. This calculation helps identify unmeasured charged particles that can cause acidosis. By subtracting the main anions from the main cation, doctors can find hidden acids in the body.

Anion Gap = [Na+] - ([Cl-] + [HCO3-])

Where:

  • [Na+] is Sodium
  • [Cl-] is Chloride
  • [HCO3-] is Bicarbonate

Steps to calculate:

  1. Add the Chloride and Bicarbonate values together.
  2. Subtract this sum from the Sodium value.
  3. The result is the anion gap, which usually falls between 8 and 12 mEq/L.

Using this standard formula ensures your results align with common laboratory reference ranges.

What Your Anion Gap Means

This number helps you understand if the body has excess acid or a loss of base. It is a crucial signal for identifying the specific type of metabolic acidosis a patient is experiencing.

  • Normal Range (8-12 mEq/L): The body is likely maintaining a healthy electrolyte balance. No significant unmeasured anions are present.
  • Elevated Gap (>12 mEq/L): This indicates high anion gap metabolic acidosis. Common causes include kidney failure, lactic acidosis, or ketoacidosis.
  • Low Gap (<8 mEq/L): A low gap is rare and often caused by low albumin levels or laboratory error. It may also indicate multiple myeloma.

Important Note

Albumin is a major negative charge that affects the gap. If albumin is low, the gap will appear falsely low. You must correct for albumin levels in critically ill patients.

This calculator is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Use this tool regularly to monitor changes in a patient's status and evaluate how well they respond to treatments for acid-base imbalances.