Cortisol, Serum (Mass Concentration)

Why This Test Might Be Ordered

Your healthcare provider may recommend this test to evaluate adrenal gland function, assess for conditions like Cushing’s syndrome (excess cortisol) or Addison’s disease (low cortisol), or check cortisol levels during stress or certain medical procedures.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if timing your cortisol levels around a specific time of day (e.g., morning peak). Avoid caffeine or alcohol before testing.

How the Test Is Performed

A blood sample is taken from a vein in your arm by a healthcare professional. The sample is then sent to a lab for analysis using a sensitive immunoassay method to measure cortisol concentration.

What the Results Mean

Results are typically reported as a mass concentration (e.g., micrograms per deciliter or nanograms per milliliter). Interpretation depends on whether the test was done at a single time or over 24 hours, or if multiple samples were taken (e.g., for a cortisol rhythm test).