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Cortisol Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Cortisol Test

A cortisol test measures the levels of the "stress hormone" in your blood, urine, or saliva to help diagnose adrenal or pituitary gland disorders.

What is a cortisol test?

A cortisol test measures the level of cortisol in your blood, urine, or saliva. Cortisol is a hormone made by your adrenal glands that affects almost every organ and tissue in your body. It helps you respond to stress, reduce inflammation, control blood glucose and metabolism, and regulate blood pressure.

Your pituitary gland makes ACTH, a hormone that tells your adrenal glands how much cortisol to make. If your cortisol levels are too high or too low, it may indicate a problem with your adrenal or pituitary glands.

What is it used for?

The test helps diagnose or rule out conditions such as:

  • Cushing's syndrome: A disorder caused by high cortisol levels over a long period.
  • Addison disease: A condition where damaged adrenal glands cannot make enough cortisol.
  • Secondary adrenal insufficiency: A condition where the pituitary gland fails to make enough ACTH to stimulate cortisol production.

Why do I need a cortisol test?

You may need this test if you show symptoms of cortisol imbalance:

  • Symptoms of Cushing's syndrome (too much): Weight gain, round face, thin arms and legs, fat deposits around the neck/shoulders, easy bruising, purple streaks on the skin, and muscle weakness.
  • Symptoms of Addison disease/adrenal insufficiency (too little): Long-lasting fatigue, muscle weakness, loss of appetite, weight loss, and abdominal pain.

What happens during a cortisol test?

Because cortisol levels vary throughout the day, your provider may order different types of tests:

  • Blood test: A sample is drawn from a vein, usually twice in one day (morning and afternoon).
  • Urine test: Often a "24-hour urine sample" where you collect all urine over a full day in a provided container.
  • Saliva test: You may collect samples at home using a swab or by spitting into a tube, following specific timing instructions.

Will I need to do anything to prepare for the test?

Preparations depend on the test type. Stress and exercise can raise cortisol, so you may need to rest before the test. Inform your provider about all medicines you use, including skin creams, but do not stop taking any medication without consulting them first.

What do the results mean?

A cortisol test alone cannot diagnose the cause of abnormal levels. High levels may be linked to Cushing's syndrome, steroid medication use, or tumors. Low levels may indicate Addison disease or secondary adrenal insufficiency. Other factors like stress, pregnancy, exercise, and birth control pills can also affect results.

Is there anything else I need to know about a cortisol test?

Some people experience pseudo-Cushing's syndrome, where high cortisol levels come and go. This can be caused by depression, anxiety, alcohol use disorder, poorly controlled diabetes, or obesity.

Frequently Asked Questions

While mild fatigue is common with low cortisol, dangerous adrenal insufficiency (Addisonian crisis) presents with severe, sudden symptoms including extreme weakness, fainting, severe abdominal pain, vomiting, and a rapid drop in blood pressure. If you experience these symptoms, especially if you have a known history of adrenal issues, seek emergency care immediately, as this is a life-threatening condition that requires rapid hormone replacement therapy.
Cortisol production follows a strict circadian rhythm, peaking in the early morning (usually between 6 AM and 8 AM) and dropping to its lowest point around midnight. A morning blood test is the standard baseline because it captures the highest natural level. If you take the test in the afternoon, your levels will naturally be lower, which could lead to a misdiagnosis of adrenal insufficiency (low cortisol) even if your glands are functioning normally.
Oral corticosteroids, such as prednisone, can significantly interfere with cortisol testing because they suppress your body's natural production of cortisol and ACTH. If you are taking these medications, your provider may need to pause them for a specific period before the test or use alternative diagnostic methods. Never stop taking prescribed steroids without medical guidance, as this can cause an adrenal crisis, but always inform your lab and doctor of your current medication list to ensure accurate interpretation.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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