Cortisol, Free (Serum or Plasma)

Why Is This Test Done?

Your doctor may order a free cortisol test to diagnose or monitor conditions like Cushing’s syndrome (a hormonal disorder causing high cortisol levels), adrenal insufficiency (when your adrenal glands don’t produce enough cortisol), or to check for adrenal gland tumors. It can also help evaluate symptoms such as unusual weight changes, fatigue, or mood swings that may be linked to hormonal imbalances.

What to Expect Before the Test

No special preparation is needed for this test. You’ll have a small needle inserted into a vein in your arm, and a blood sample will be drawn. If you’re taking medications that affect cortisol levels (like some steroids), your doctor may ask you to stop them temporarily or adjust your timing.

What the Results Mean

Free cortisol levels can vary based on your time of day, stress levels, and overall health. Your results will be compared to standard reference ranges provided by your lab. High levels might suggest Cushing’s syndrome or other conditions, while low levels could indicate adrenal problems.

Common Conditions This Test Helps Diagnose

This test is often used alongside other tests to diagnose conditions like Cushing’s syndrome, adrenal insufficiency, or to check for abnormal cortisol production from tumors in your adrenal glands.