Cortisol Blood Test
Tests & Procedures

Cortisol Blood Test – Fasting, Preparation, Procedure And Interpretation Of Results

5 min read May 1, 2019

What Is Cortisol?

Cortisol, also known as hydrocortisone is a Major Glucocorticoid Hormone (Steroid Hormone) which is synthesized from cholesterol by the adrenal gland located above the kidneys.

Cortisol hormone supports the following systems of the human body:

  • Immune system
  • Nervous system
  • Circulation
  • Digestive system
  • Musculoskeletal system

Cortisol hormone is normally produced throughout the day. It is secreted maximally early in the morning and gradually decreases to lower levels until early afternoon.

The Level Of Cortisol In Blood Spikes

Why Is Cortisol Important?

Cortisol is an important hormone which mediates the fight-or-flight response in humans. The body releases cortisol to pause certain bodily functions such as growth processes, reproductive system, and immune response. On the other hand, cortisol also contributes to some of the essential functions of the human body such as

  • Response to stress
  • Fights against infections
  • Regulation of blood sugar levels and insulin resistance
  • Maintain blood pressure
  • Regulation of metabolism of fats, proteins, and carbohydrates

Why Is Cortisol Blood Test Done?

A Cortisol blood test may be advised to diagnose disorders of the adrenal glands such as Addison’s disease or Cushing’s syndrome or to monitor the effectiveness of therapy for these disorders. Disorders of the adrenal glands may have serious complications if not addressed and treated timely since cortisol directly or indirectly acts on every organ or tissue of the body.

How Do You Prepare For The Test?

Since Cortisol levels vary at different times of the day, the timing at which blood sample is collected is important. A blood cortisol test is usually done in the morning when the levels are highest. Your doctor may, however, schedule your cortisol blood test at two different times in a day – one early in the morning and one in the afternoon when the Cortisol levels are much lower.

A Cortisol Blood Test May Need The Following Preparations

  • Generally, fasting is not required for a cortisol blood test.
  • Since cortisol is released in response to stress, it is a usual advise by doctors to remain stress-free when reporting for the test.
  • You may be advised to withhold certain medications, health supplements, and herbal medicines before planning for the test.

Certain medicines may have to be stopped at least 24-48 hours before the test. Some medications which may alter blood cortisol levels and give incorrect results include

  • Synthetic glucocorticoids such as steroid drugs
  • Medicines containing estrogen such as oral contraceptives
  • Phenytoin (anti-epileptic drugs)
  • Androgen containing medicines

[Read – Blood Tests That Require Fasting List]

How Is The Test Performed?

The cortisol blood test requires the collection of the blood sample.

  • A blood sample will be collected by a nurse or a technician in a laboratory or the doctor’s clinic.
  • The patient will be required to sit in a chair with a hand placed on the armrest.
  • A tourniquet will be tied to the arm just above the site from which the blood sample has to be collected. This stops blood flow and makes the veins more prominent making it easier to collect blood.
  • The site from where blood has to be collected is sterilized using alcohol.
  • A needle will be inserted into the vein and a small amount of blood sample will be collected in a syringe. This might cause slight pinprick-like pain.
  • Once the blood sample has been collected, the tourniquet is loosened and a small cotton swab is placed at the site and you need to apply slight pressure to stop blood from oozing out.
  • A bandage may be placed to secure the cotton swab.
  • You may notice slight bruising or soreness at the site of venepuncture. This goes away within a few days without any specific treatment.

Cortisol Blood Test Levels

Reference Range For Blood Cortisol Levels Is

Early morning (6-8 am): 10 – 20 microgram per deciliter (mcg/dl)

Afternoon (around 4 pm): 3 – 10 micrograms per deciliter (mcg/dl)

We already know that cortisol levels in the blood are different at different times of the day. Apart from the timing of blood sample collection, cortisol test results tend to be influenced by or even depend upon several factors such as:

  • Age
  • Gender
  • General health status
  • Family history
  • Pregnancy in women
  • Amount of physical or emotional stress
  • History of being on medications for certain other medical conditions.
  • Timing of blood collection
  • Kit used for testing

Test Results And Interpretation

Any cortisol blood test result below or above the normal reference range is considered to be abnormal and needs to be addressed immediately.

High levels of cortisol in the blood are diagnostic of Cushing’s syndrome. However, high levels do not necessarily mean that you have an abnormally functioning adrenal gland.

High Cortisol Levels Can Also Be Present Under Certain Other Conditions Such As

  • Pregnancy especially during the last trimester
  • Athletes who train heavily
  • Acute infections
  • Physical or emotional stress
  • Tumor of the adrenals, pituitary glands or at some other location which may be producing excess cortisol
  • Depression, anxiety and panic disorders
  • Malnutrition status
  • Alcoholism

Low Cortisol Levels Are Suggestive Of The Following Conditions

  • Addison’s Disease – Adrenal glands do not produce enough cortisol
  • Hypopituitarism – A disorder of the pituitary gland due to which production of cortisol by adrenals is poor

Altered cortisol levels are also often found among individuals who work in night shifts. An altered circadian cycle is also known to influence blood cortisol levels.

If blood cortisol levels are not normal, your doctor may advise some more blood, urine or radiological tests to diagnose the underlying cause for abnormal test results. A CT scan or an MRI may also be advised which will help to view the adrenal glands, pituitary gland or tumors to understand the possible causes for the abnormal secretion of cortisol.

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