: Anion Gap, Fluid, Calculated, Substance Concentration

: What This Test Measures

: The anion gap is not measured directly; it is calculated from the concentrations of major electrolytes in the fluid sample, typically sodium, chloride, and bicarbonate (and sometimes potassium). The result reflects the gap between positively charged ions (cations) and negatively charged ions (anions).

: Why It May Be Ordered

: Your healthcare provider may order this calculation to evaluate the balance of electrolytes and acids in a body fluid. It can help identify the presence of unmeasured ions and support the assessment of certain metabolic or fluid-related conditions.

: How the Calculation Is Done

: The laboratory uses the electrolyte results from your fluid specimen to compute the gap mathematically. Because it is a calculated value, its accuracy depends on the accuracy of the underlying electrolyte measurements.

: What the Results Can Mean

: An altered anion gap may suggest an accumulation of unmeasured acids or other ions, or a change in electrolyte concentrations. Interpretation depends on the type of fluid sampled and the clinical context, so results should always be reviewed by your provider.