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What is cortisol test?

Cortisol test measures the amount of cortisol, a hormone produced by adrenal glands (the glands located above kidneys) in blood. This test is also known as blood cortisol or plasma cortisol test. It is mainly used to diagnose Addison disease and Cushing syndrome, two rare medical conditions marked by cortisol imbalance. However, this test also detects other diseases that affect adrenal and pituitary function.

  1. Why is cortisol test performed?
  2. How do you prepare for cortisol test?
  3. How is cortisol test performed?
  4. Cortisol test results and normal range

Cortisol test is done to detect decreased or increased cortisol production in the body, which occurs due to Addison's disease and Cushing's syndrome. Cortisol is a significant component of the immune, nervous and circulatory systems. It plays an important role in the metabolism of proteins and fats and in stimulating stress responses. Doctors recommend this test if they observe signs of less cortisol or symptoms of Addison's disease, such as:

A cortisol test is also recommended when signs of excess cortisol or symptoms of Cushing syndrome are seen; such as:

Furthermore, this test is ordered if the following symptoms of adrenal crisis are observed:

Before a blood sample is collected for the test, you might be asked to rest to reduce stress levels. If a saliva sample is required for the test, you might be told to avoid brushing teeth, eat or drink for about 15 to 30 minutes before the test.

It is important to inform the healthcare provider if you are taking any vitamins, medicines, illicit drugs, supplements, herbs, non-prescribed medications and vitamins since these may interfere with results.

For a cortisol test, a blood sample is withdrawn from a vein in the arm after swabbing the concerned area with an antiseptic solution. As cortisol levels change throughout the day, the test is typically performed twice, once in early morning and once at about 4 p.m. on the same day. A saliva sample or a 24-hour urine sample might also be taken.

Though the test is generally safe, there is a slight risk of bleeding, getting infected or bruised and feeling lightheaded after the withdrawal of blood sample. Also, some people may experience mild pain while the sample is being drawn.

Results of this test vary based on different factors like the method used for carrying out the test, your age, gender and health history.

Normal results:

Cortisol levels are typically on the lower side of normal at about midnight and on the higher side of normal in the early morning. Although the normal range for cortisol varies from laboratory to laboratory and the time of withdrawal of blood sample, the commonly used normal range is:

  • 10 to 20 mcg/dL between 6 to 8 p.m.
  • 3 to 10 mcg/dL at about 4 p.m.

Abnormal results:

Abnormal cortisol levels indicate:

  • Long-term consumption of glucocorticoid medications, e.g., those taken for asthma, inflammation or autoimmune diseases
  • Cushing syndrome (excess cortisol)
  • Secondary adrenal insufficiency

Cortisol levels are seen to be high when a person experiences trauma or stress or performs any physical activity before the test. Highly trained athletes; women in the last 3 months of their pregnancy; and people with panic disorder, depression, malnutrition or alcoholism might also have higher levels of cortisol.

Disclaimer: All results must be clinically correlated with the patient's complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.  


  1. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Cortisol level
  2. Stewart PM, Krone NP. The adrenal cortex. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Saunders Elsevier; 2011: chap 15.
  3. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Cortisol (Blood)
  4. Pagana, K. D., Pagana, T. J., and Pagana, T. N. (©, 2015). Mosby's Diagnostic & Laboratory Test Reference 12th Edition: Mosby, Inc., Saint Louis, MO. Pp 301-303.
  5. John E. Morley. Merck Manual Professional Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2019. Overview of the Endocrine System
  6. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Cortisol Test
  7. Benioff Children's Hospital [internet]: University of California, San Francisco; Cortisol Level
  8. National Institute of Diabetes and Digestive and Kidney Diseases [internet]: US Department of Health and Human Services; Cushing's Syndrome
  9. Thau L, Sharma S. Physiology, Cortisol. [Updated 2019 Feb 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan.

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