Cortisol, Free (Serum/Plasma)

Why Is This Test Done?

Your healthcare provider may order this test to check for conditions affecting your adrenal glands, such as Cushing’s syndrome (overproduction of cortisol) or Addison’s disease (underproduction of cortisol). It can also help diagnose issues like adrenal insufficiency, stress-related hormone imbalances, or certain types of tumors.

What Does the Result Mean?

Results may be compared to your baseline levels or to those of others with similar conditions. High levels could suggest overactive adrenal glands or certain medications. Low levels may indicate problems with your adrenal glands or pituitary gland. Your provider will interpret the results in the context of your symptoms and medical history.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. You may feel a small pinch when the needle is inserted, but the procedure usually takes only a few minutes. The sample is then sent to a lab for analysis using a sensitive immunoassay method to measure free cortisol levels accurately.

What Can Affect Results?

Several factors can influence cortisol levels, including stress (physical or emotional), certain medications (like steroids), time of day, recent meals, or even the timing of the blood draw. If you’re taking any medications or have recent stress, your provider may ask you to adjust your schedule or timing for the test.