Dexamethasone suppression test
- Requires a medical indication
1 mg dexamethasone suppression test, also known as the Nugent test. Dexamethasone is taken at night and cortisol is measured first thing the following morning to check whether it has been suppressed. It is a screening test for Cushing's syndrome that requires a medical indication and a prescription to obtain the medicine.
For this test you have to take 1 mg of dexamethasone the night before, and dexamethasone is a prescription-only medicine. We issue the test request; the prescription has to come from your doctor. In addition, the result is not reliable in women taking oestrogen-containing contraceptives, or during pregnancy.
What it is for
It is used to investigate whether cortisol production is suppressed after dexamethasone is given. Under normal conditions, the medicine reduces the pituitary signal and cortisol falls the following morning.
It is a sensitive test for screening for Cushing's syndrome, but a non-suppressed result does not confirm the disease. It can be due to medicines, oestrogens, variable absorption or metabolism of dexamethasone and other situations that need to be reviewed.
When it is recommended
- Medical suspicion of Cushing's syndrome when this screening test has been chosen
- Shifted sleep schedules that make late-night salivary cortisol difficult to interpret
- Investigation of an adrenal lesion with possible autonomous cortisol production
- It is not usually suitable during pregnancy or while taking oral oestrogens, because they can raise total cortisol
Clinical comment
This test has high sensitivity but more limited specificity. That means it works well for not missing cases, at the cost of non-suppressed results in people who turn out not to have Cushing's syndrome.
Some antiepileptic medicines, rifampicin and other medicines speed up the elimination of dexamethasone. If the body receives less exposure than expected, cortisol may not be suppressed even though the axis is normal. Oral oestrogens increase the carrier protein and can raise total cortisol.
Bear in mind that this order includes the test request, but not the prescription for dexamethasone. The doctor who indicates the test must prescribe the tablet, review your medication and explain the exact time to take it. With borderline results, it can be useful to measure the dexamethasone concentration, a test that is not included in this profile.
Dr. Antonio Mas
What is tested
• Cortisol: Measured between 8:00 and 9:00 in the morning after taking 1 mg of dexamethasone the night before. The result shows whether the hormonal axis has responded to the expected brake.
- Cortisol
How to prepare
Follow your doctor's instructions exactly: usually 1 mg of dexamethasone is taken between 23:00 and 24:00 and the sample is taken between 8:00 and 9:00 the following morning, after 8 hours of fasting.
Report antiepileptic medicines, rifampicin, oestrogens and corticosteroids of any kind. Do not do the test if you do not have the prescription and the instructions from the doctor who has indicated it.
You can add
Without another needle. It is offered when you order, so you do not have to decide now.
- General blood testA general blood test with full blood count, glucose, cholesterol and kidney and liver function: the basic parameters included in any general check-up.+€59.00
- General + nutritional blood testEverything in the general blood test (anaemia, kidneys, liver, cholesterol and glucose) plus iron stores, vitamin D, vitamin B12 and folic acid. It is the broadest add-on: it covers the general and the nutritional in one go.+€129.00
Related blood tests
We have other profiles in Other tests with more or fewer tests:
- Basal blood cortisol€39.00
- 24-hour urine free cortisol€49.00
- Late-night salivary cortisol€59.00
- High calcium, PTH and mineral metabolism€89.00
- Cortisol assessment, in saliva and urine€99.00
- High prolactin assessment€149.00
- Metabolic assessment of kidney stones (blood and 24-hour urine)€179.00
- Pituitary hormone profile€199.00
The most comprehensive is not always the most useful. If you are not sure, the one we recommend to start with is High prolactin assessment.
What it is based on
Pituitary Society · Lancet Diabetes Endocrinol 9(12):847-875
Consensus on diagnosis and management of Cushing's disease: a guideline update
The cut-off of 1.8 µg/dL (50 nmol/L) and the two figures on this page come from table 1 of this consensus: 98% sensitivity, the highest of the three tests, and 81% specificity, the lowest. It is also the source of the situation in which this test is preferred, shift work and shifted sleep patterns, and of the one in which it is not advised: it may be unreliable in women taking oral oestrogens.
Endocrine Society · J Clin Endocrinol Metab 93(5):1526-1540
The Diagnosis of Cushing's Syndrome: An Endocrine Society Clinical Practice Guideline
Places the 1 mg dexamethasone suppression test among the three accepted screening tests and leaves the choice between them to what suits each person. That is what supports having all three in the catalogue instead of just one.
Protocol designed by Dr. Antonio Mas, specialist in Endocrinology and Nutrition, Spanish medical licence no. 080846289, and reviewed in September 2026.
This blood test is a standardised protocol and does not replace a medical consultation. If you have symptoms, a known condition or a complex clinical situation, speak to your doctor.