What is a Diurnal Cortisol Test?

Testing measuring your cortisol levels throughout the day, from the moment you wake up until you go to bed, is called diurnal cortisol testing. They can aid in the visualisation of your adrenal gland function by a medical practitioner.

The hormone cortisol is produced by the body from cholesterol. It performs a multitude of tasks, including immune system regulation and sleep-wake cycle maintenance.

Most people associate cortisol with the body's stress hormone. It assists your body in maintaining a state of heightened arousal throughout stressful conditions.

Your cortisol levels throughout the day are displayed by a diurnal cortisol test. This is all the information you need to take the test.

What is a diurnal cortisol test?

Your cortisol levels are measured multiple times a day, usually after you wake up, before lunch, before dinner, and before bed, using a diurnal cortisol test. The test allows you to see changes in your cortisol levels over time by collecting multiple samples.

Healthcare practitioners can gain additional knowledge about your endocrine system, which regulates hormone secretions, with the use of diurnal cortisol testing. To identify issues with the adrenal gland, which is responsible for producing cortisol, doctors frequently perform cortisol testing.

Moreover, it aids in the diagnosis of pituitary gland issues. Adrenocorticotropic hormone (ACTH), which is produced by the pituitary gland, causes the adrenal glands to secrete more cortisol.

Who should take a diurnal cortisol test?

If a medical practitioner needs more details regarding your endocrine system, they will request a diurnal cortisol test.

A diurnal cortisol test can be taken by almost everyone. Tests for cortisol in the urine and saliva are noninvasive and have no known hazards. In addition to being minimally invasive, blood cortisol tests include a very small risk of extremely minor adverse effects, like little soreness and bruising where the blood is taken.

Do you have to prepare for a diurnal cortisol test?

You will receive instructions from your healthcare provider on how to get ready for a diurnal cortisol test. Pay close attention to their directions if you want reliable outcomes.

On the day of the test, it's crucial to make an effort to unwind because stress might increase cortisol levels. Furthermore, you might need to abstain from physical activity the day before some diurnal cortisol tests.

Additionally, you may need to stay away from some drugs and skin care products, especially ones that include steroids. However, it's crucial to consult your physician beforehand.

Lastly, you should wait at least 30 minutes before doing a saliva test before eating, drinking, or brushing your teeth.

Diurnal cortisol test steps

You can test for cortisol at home, but the results need to be sent to a lab. The majority of diurnal cortisol samples are taken with saliva at home. You will receive instructions from your doctor on when to take tests during the day.

Saliva sample storage tubes and up to four swabs are included in a diurnal cortisol test kit. Observe the test instructions, which may comprise the following general steps:
  • Wash and pat dry your hands thoroughly.
  • Take the swab out of its box without making contact with the absorbent portion.
  • For two minutes, place the swab inside your mouth and move it around to ensure that all of your saliva is covering it.
  • After taking it out, put the swab back into the tube. (Instead of putting a swab in your mouth, certain tests could ask you to spit into a tube.)
  • Place the tube's cover on and tighten it. Put it inside the test kit's container, which is usually an envelope or plastic bag.
  • As directed by the package, label your sample. The majority of kits ask you to write the time on the plastic bag, envelope, or test tube itself.
  • Once you've collected all the necessary samples, follow the instructions and deliver the test kit to a lab or doctor's office.

Interpreting diurnal cortisol test results

Results from daily cortisol tests differ greatly between individuals depending on age, sex, and health.

Your doctor may be examining your diurnal cortisol slope or the variation in your cortisol levels from dawn to dusk.

Your physician may observe:
  • Low cortisol (hypocortisolism): Addison's disease, often known as adrenal insufficiency, is indicated by low cortisol levels. It's typically associated with an autoimmune disease that triggers the immune system to target the adrenal gland.
  • High cortisol (hypercortisolism): Cushing's syndrome is the term for excessive cortisol levels. Pituitary or adrenal gland tumours as well as long-term corticosteroid use can cause Cushing's syndrome.
  • A flat diurnal cortisol slope: When your cortisol levels don't significantly fluctuate between the hours of dawn and night, you have flat diurnal cortisol slopes. In a 2017 research, the authors discovered that lower levels of cortisol during the day were linked to several detrimental health consequences, including obesity, anxiety, depression, and chronic fatigue syndrome.

Next steps after taking a diurnal cortisol test

Your physician can assist you in interpreting the results of your diurnal cortisol test and deciding on the best course of action.

You may be able to stop here if your results are typical. To confirm the diagnosis of an underlying disease, your doctor may recommend further testing if your findings are abnormally high or low.

Where can you get a diurnal cortisol test and what are the costs?

A medical practitioner will instruct you on how to administer a diurnal cortisol test if they recommend one. Usually, testing is available on-site at hospitals and clinics, or a saliva test kit can be purchased for self-testing.

A diurnal cortisol test kit costs $75 to $100 when purchased online. Your insurer probably won't pay for the test if your doctor didn't order it.


If the results of a diurnal cortisol test are not within normal ranges, it could indicate an imbalance in hormones that needs to be treated.


What is a normal diurnal cortisol level?

10 to 20 micrograms per deciliter (mcg/dL)

Why do you need to check cortisol in the morning?

Release of cortisol is greatest during early morning waking hours

How do you check cortisol levels during the day?

Blood samples are usually taken twice during the day

What is a dangerously low cortisol level?

Low single-digit readings or essentially no cortisol production.

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