Cortisol (mass concentration) in serum/plasma

Why Is This Test Done?

Doctors may order cortisol testing to diagnose conditions like Cushing’s syndrome (too much cortisol), Addison’s disease (too little cortisol), or to 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 usually needed, but if your doctor suggests timing your test around specific events (like stress or certain times of day), follow their instructions carefully. You may need to fast for 8–12 hours before blood is drawn, depending on the test type.

How the Test Is Performed

A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. The sample is then sent to a lab for analysis using a sensitive immunoassay method to measure cortisol concentration.

Possible Results and Interpretation

Results are compared to standard reference ranges, but individual ranges can vary. Low cortisol may indicate adrenal insufficiency, while high levels could signal overproduction due to conditions like tumors or chronic stress. Your doctor will discuss findings in relation to your symptoms and medical history.