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
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
- 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.
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.
Overnight dexamethasone suppression test
Cortisol level is less than 5
micrograms per deciliter (mcg/dL) or less than 138
nanomoles per liter (nmol/L).
High cortisol levels may be caused
- 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.