Description

Cortisol is a vital hormone produced by your adrenal glands that follows a natural daily rhythm. Levels peak shortly after waking and drop to their lowest at night. Measuring cortisol in the morning provides a reliable snapshot of adrenal function and can help diagnose disorders of over- or under-production.

Clinical Uses

  • Diagnose adrenal insufficiency (Addison’s disease)
  • Screen for Cushing’s syndrome (excess cortisol)
  • Evaluate chronic fatigue or unexplained weight changes
  • Assess HPA axis disorders (hypothalamic-pituitary-adrenal dysfunction)
  • Monitor treatment for known adrenal or pituitary conditions

Test Details & Patient Preparation

  • Specimen Type: Venous blood draw
  • Timing: Within 2 hours of waking—ideally between 6 AM and 9 AM
  • Preparation:
  • No fasting required
  • Avoid strenuous exercise, caffeine, and high-stress activities before the draw
  • Note exact wake-up and draw times for accurate interpretation

Why Morning Matters:

Because cortisol levels fluctuate widely throughout the day, a morning specimen captures the peak. Abnormally high or low values at this time may indicate adrenal or pituitary disorders and may lead to additional testing, such as late-night salivary cortisol or dexamethasone suppression, to assess daily variation and feedback mechanisms.