What does the Cortisol, single time-point (Saliva) test measure?

Why is Cortisol, single time-point (Saliva) measured?

A single salivary cortisol is most often ordered as part of a hormone panel rather than for adrenal diagnosis. Late-night salivary cortisol is validated for Cushing syndrome screening, but a daytime or unspecified-time result has limited diagnostic value and should not be used to diagnose adrenal insufficiency or hypercortisolism. Functional practitioners interpret single values in the context of symptoms, but this approach lacks robust evidence.

Reference ranges

Standard reference

Morning (waking) approximately 3.7–9.5 ng/mL; afternoon approximately 1.2–3.0 ng/mL; evening/bedtime approximately 0.4–1.0 ng/mL. Interpretation depends on the collection time.

Functional medicine optimal

For a late-night (bedtime) sample, values below 1.0 ng/mL are typically normal; elevation above that threshold warrants further evaluation for Cushing syndrome. For waking or daytime samples, optimal ranges are defined by the time of collection and the clinical question, and single-point interpretation is fraught with biological variability.

Units

ng/mL, nmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.