Skip to content
Font Size
A
A
A

Overnight Dexamethasone Suppression Test

Results

The overnight dexamethasone suppression test involves taking a dose of a corticosteroid medicine called dexamethasone to see how it affects the level of a hormone called cortisol in the blood. This test screens for Cushing's syndrome, a condition in which excess amounts of cortisol are being produced by the adrenal glands. Test results are usually available in a few days.

An abnormal test result may mean that further testing is needed to identify Cushing's syndrome. Likewise, a normal test result means that you do not have Cushing's syndrome. Cushing's syndrome can be hard to diagnose, so an endocrinologist should be consulted if test results are uncertain or if the test results do not help explain your symptoms.

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Normal

Overnight dexamethasone suppression test 1
Normal:

Cortisol level is less than 5 micrograms per deciliter (mcg/dL) or less than 138 nanomoles per liter (nmol/L).

High values

High cortisol levels may be caused by:

  • Cushing's syndrome.
  • Other health problems, such as a heart attack or heart failure, fever, poor diet, an overactive thyroid gland (hyperthyroidism), depression, anorexia nervosa, uncontrolled diabetes, or alcoholism.
  • Cancers that make ACTH, such as lung cancer.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Pregnancy or extreme obesity.
  • Severe weight loss, dehydration, or acute alcohol withdrawal.
  • Severe injury.
  • Diabetes.
  • You take medicines, such as barbiturates, phenytoin (Dilantin), birth control pills, aspirin, morphine, methadone, lithium, monoamine oxidase inhibitors (MAOIs), spironolactone (Aldactone), or diuretics.

Some people may quickly process (metabolize) the dose of dexamethasone. In these people, cortisol levels will not drop unless a higher dose of the medicine is given.

WebMD Medical Reference from Healthwise

Last Updated: November 14, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

Hot Topics

WebMD Video: Now Playing

Click here to wach video: Dirty Truth About Hand Washing

Which sex is the worst about washing up? Why is it so important? We’ve got the dirty truth on how and when to wash your hands.

Click here to watch video: Dirty Truth About Hand Washing

Popular Slideshows & Tools on WebMD

disciplining a boy
Types, symptoms, causes.
psoriasis
Does your kid have symptoms?
fruit drinks
Eat these to think better.
No gym workout
Moves to help control blood sugar.
acupuncture needle on shoulder
10 tips to look and feel good.
Close up of eye
12 reasons you're distracted.
Epinephrine Injection using Auto-Injector Syringe
Life-threatening triggers.
woman biting a big ice cube
Habits that wreck your teeth.
embarrassed woman
Do you feel guilty after eating?
pacemaker next to xray
Treatment options.
caregiver with parent
10 tips for daily life.
birth control pills
Which kind is right for you?

Pollen counts, treatment tips, and more.

It's nothing to sneeze at.

Loading ...

Sending your email...

This feature is temporarily unavailable. Please try again later.

Thanks!

Now check your email account on your mobile phone to download your new app.

Women's Health Newsletter

Find out what women really need.