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Overnight Dexamethasone Suppression Test

How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks

Risks of a blood test

There is very little chance of a problem from having a blood sample taken from a vein.

  • You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
  • In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
  • Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.
  • Bruising may be more likely in people with high ACTH and cortisol levels.

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 test1
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:

WebMD Medical Reference from Healthwise

Last Updated: May 17, 2012
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.

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