Clinical Significance of Anion Gap 6 mEq/L
An anion gap of 6 mEq/L is within the normal range using modern ion-selective electrode methodology and does not indicate metabolic acidosis or require urgent intervention. 1, 2
Understanding the Normal Range
The reference range for anion gap has shifted downward from the traditional 8-16 mEq/L to 3-11 mEq/L (or 5-12 mEq/L) with modern laboratory analyzers, primarily due to changes in chloride measurement techniques using ion-selective electrodes. 2, 3, 4
A value of 6 mEq/L falls comfortably within the current normal range and should not be interpreted using outdated reference values. 2, 4
An anion gap below 3 mEq/L should be considered abnormally low, not a value of 6 mEq/L. 2
What This Value Rules Out
This anion gap excludes high anion gap metabolic acidosis, which requires values >12-13 mEq/L and is incompatible with toxic ingestions (ethylene glycol, methanol, salicylates) that produce markedly elevated anion gaps typically >22 mEq/L. 1
Diabetic ketoacidosis is ruled out, as DKA typically presents with anion gaps ≥22 mEq/L. 1
Lactic acidosis and uremic acidosis are also excluded by this normal value. 1
Recommended Evaluation
First, verify the laboratory measurement and check for quality control issues with electrolyte measurement, then recalculate the anion gap using the formula: Na+ - (Cl- + HCO3-). 1
Check arterial blood gases to confirm the absence of metabolic acidosis (pH should be normal, bicarbonate should be normal). 1
No further workup is needed if the patient is asymptomatic and other electrolytes are normal. 1
Clinical Context
The majority of normal individuals using modern analyzers can be expected to have serum anion gaps of 6 mEq/L or less. 4
Clinicians must be aware that the traditional reference range (8-16 mEq/L) is no longer appropriate with modern instrumentation, and continued use of outdated values may lead to misinterpretation. 3, 4