Cortisol, Serum (Mass Concentration)

Why This Test Is Done

Your healthcare provider may order a serum cortisol test to diagnose or monitor conditions such as adrenal gland disorders (e.g., Cushing’s syndrome or Addison’s disease), evaluate stress responses, or check for hormone imbalances. It may also be used to assess pituitary-adrenal axis function or evaluate symptoms like fatigue, weight changes, or unusual mood swings.

How the Test Is Performed

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab for analysis using a sensitive method to measure cortisol concentration.

What to Expect Before the Test

No special preparation is typically needed, but you may be advised to fast for 8–12 hours before the test if timing your cortisol levels around natural fluctuations (e.g., morning/evening) is important. If you’re taking medications that affect cortisol, inform your provider.

Possible Results and Their Meaning

Results are interpreted based on your clinical symptoms and timing (e.g., morning vs. evening samples). Abnormal results may indicate overproduction (e.g., Cushing’s syndrome) or underproduction (e.g., adrenal insufficiency) of cortisol, which can cause symptoms like high blood pressure, muscle weakness, or unexplained weight changes.