Anion Gap Calculator

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Analyze electrolyte balance and diagnose types of metabolic acidosis.

Serum Electrolytes

Sodium (Na+)

mEq/L

Chloride (Cl-)

mEq/L

Bicarbonate (HCO3-)

mEq/L

Potassium (K+) (Optional)

mEq/L

Disclaimer: This tool is for clinical reference. Always interpret lab results in the context of the patient's full clinical presentation.

Calculated Gap

Enter serum electrolyte levels to calculate the primary anion gap.

About this calculator

Overview

The Anion Gap is a calculated value used to identify the cause of metabolic acidosis (an excess of acid in the body). It represents the difference between measured cations (positively charged ions like Sodium) and measured anions (negatively charged ions like Chloride and Bicarbonate). A high gap suggests the presence of unmeasured acidic anions, such as lactate or ketoacids.

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Pro Tips

If a patient's Albumin is low, the 'normal' anion gap should be adjusted downward.
Ensure lab samples haven't been sitting for too long, as bicarbonate levels can decrease over time in a test tube.
Anion gap calculations are most useful when interpreted alongside blood gas (pH) results.
Always double-check lab values if the resulting anion gap seems mathematically Impossible (e.g., negative).

Fun Facts

"A typical healthy anion gap is between 8 and 12 mEq/L (if Potassium is not included)."
"High Anion Gap Metabolic Acidosis (HAGMA) is often remembered by the mnemonic MUDPILES (Methanol, Uremia, DKA, etc.)."
"Low anion gaps are rare and can be caused by low albumin levels or high levels of cations like Calcium or Magnesium."
"Potassium is sometimes included in the calculation, but its low concentration makes it optional in most clinical settings."

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