Plasma or serum concentration of free cortisol

Why This Test Is Done

Your doctor may order a free cortisol test to check for hormonal imbalances, such as excessive cortisol production (Cushing’s syndrome) or insufficient cortisol (adrenal insufficiency). It can also help evaluate conditions like pituitary tumors or other adrenal disorders. Sometimes, it’s used alongside other tests to confirm or rule out hormone-related issues.

What to Expect Before the Test

No special preparation is needed, but you may be asked to avoid certain medications or activities for a few days before testing. If you’re taking steroids or other hormone medications, your doctor will advise you on timing. Blood is drawn from a vein, usually in your arm, and you may feel a slight pinch.

What the Test Results Mean

Free cortisol levels can vary based on time of day, stress, and medications. High levels may indicate overproduction of cortisol, while low levels could suggest adrenal problems. Your doctor will interpret results in the context of your symptoms and other tests.

Common Conditions Linked to Free Cortisol

Elevated free cortisol is often linked to Cushing’s syndrome (due to tumors or excess hormone release), while low levels may signal adrenal insufficiency, pituitary disorders, or other hormonal imbalances. It’s not a standalone diagnosis but supports broader evaluation.