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Understanding Your Medical Test: What It Is, How to Prepare, and What Your Results Mean

Published: August 9, 2026Updated: August 16, 2026

This urine test measures 17-ketogenic steroid levels after taking high-dose dexamethasone to help diagnose Cushing's syndrome.

Quick summary

{"17-ketogenic steroids are waste products from cortisol metabolism in your urine","High-dose dexamethasone should normally suppress cortisol production","This test helps distinguish between different causes of cortisol excess","A 24-hour urine collection is required","Results help doctors identify if the problem is in the pituitary, adrenal glands, or elsewhere"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
1581-8
Short code
17-KGS-24h-DST
Synonyms
17KGS pre 2 mg Dex high 24h Ur-mRate
Category
chemistry
Sample
urine
Container
24-hour urine collection container with preservative (typically boric acid or hydrochloric acid)
Units
N/A
Ref low
20
Ref high
400
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
Gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS)
CPT
80327
SNOMED
7806001
Specimen volume
Complete 24-hour urine collection (typically 1000-2000 mL total volume)
Stability
Refrigerated (2-8°C) during collection; if prolonged delay, store at -20°C. Stable for up to 7 days refrigerated, longer if frozen.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
72–168 hours
Order
routine

This test is a diagnostic tool that helps your healthcare provider evaluate how your body is functioning. It can be used to screen for a medical condition, confirm or rule out a suspected diagnosis, monitor a disease you already have, or check how well a current treatment is working. Your provider orders this test based on your symptoms, medical history, and overall health needs.

The 17-ketogenic steroids test measures the amount of steroid hormone waste products in your urine. These compounds are produced when your body breaks down cortisol, the main stress hormone. This particular test is performed after taking high-dose dexamethasone, a medication that should normally suppress cortisol production. The test helps doctors understand how your body responds to this suppression and is primarily used to diagnose Cushing's syndrome, a condition caused by excessive cortisol levels.

Preparation depends on the specific type of test being performed, so always follow the instructions from your healthcare provider. You may be asked to fast for 8 to 12 hours, avoid certain foods, drinks, medications, or supplements, or stop smoking beforehand. Drinking water is usually encouraged unless you are told otherwise, and wearing a sleeve that rolls up easily can make sample collection simpler.

Your doctor will provide specific instructions. Generally, you will need to take dexamethasone (2mg by mouth every 6 hours) for 2.5 days before the urine collection. It's important to take the medication exactly as prescribed. You should avoid strenuous exercise and maintain your normal diet. Tell your doctor about all medications you are taking, as certain drugs can affect the test results. Women should inform their doctor if they are menstruating, as this can affect results.

The test is usually performed in a laboratory, clinic, or your provider's office by a trained healthcare professional. Depending on what is being measured, it may involve drawing a small amount of blood from a vein, collecting a urine sample, taking a throat or nasal swab, or obtaining another type of specimen. Most collections take only a few minutes, and you may feel a brief pinch or mild discomfort, but serious problems are rare.

You will collect all urine produced over a 24-hour period. Start by urinating into the toilet upon waking in the morning, then collect all subsequent urine in the provided container for the next 24 hours. Keep the container refrigerated or in a cool place. Return the container to your lab or healthcare provider as instructed. The timing of urine collection in relation to your dexamethasone doses will be specified by your doctor.

Your results are compared with established reference ranges and interpreted together with your symptoms, medical history, and other findings. Results within the normal range generally suggest that no abnormality was detected, while results outside that range may point to a condition that needs closer attention. An abnormal result does not automatically mean you have a serious illness, so your provider may recommend repeat testing or additional studies before discussing a diagnosis and next steps with you.

Your test results will show whether your 17-ketogenic steroid levels were suppressed after taking high-dose dexamethasone. If levels drop significantly, it suggests the source of excess cortisol is in the pituitary gland (Cushing's disease). If levels do not drop, it may indicate an adrenal tumor or ectopic ACTH production. Your doctor will interpret these results in combination with other tests to determine the cause of your symptoms.

Reference range

Premenopausal: 20-400 pg/mL; Postmenopausal: <30 pg/mLN/A

Specimen: urine

Collect 24-hour urine specimen following high-dose dexamethasone suppression (2mg PO every 6 hours for 2.5 days). Maintain adequate hydration during collection. Avoid vitamin C supplements during collection as they may degrade preservatives. Record start and end times of collection accurately. Keep urine refrigerated or on ice during 24-hour collection period.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test is primarily used to diagnose and differentiate causes of Cushing's syndrome. It helps distinguish between pituitary-dependent Cushing's disease (where high-dose dexamethasone suppresses cortisol) and adrenal tumors or ectopic ACTH secretion (where suppression does not occur). The test is also used to monitor treatment effectiveness in patients with cortisol-producing conditions and to evaluate adrenal function in complex endocrine disorders.

Frequently asked questions

Why do I need to take dexamethasone before the test?
Dexamethasone is a synthetic steroid that normally suppresses the body's natural cortisol production. By measuring how much your 17-ketogenic steroids are suppressed (or not suppressed) after taking high-dose dexamethasone, doctors can determine where the excess cortisol is coming from in your body.
Does the dexamethasone have side effects?
Short-term use of dexamethasone for this test may cause temporary side effects such as mood changes, difficulty sleeping, increased appetite, or mild stomach discomfort. These usually resolve after the test is completed. Contact your doctor if you experience severe or unusual symptoms.
What happens if I miss a dose of dexamethasone?
It is important to take dexamethasone exactly as prescribed. If you miss a dose, take it as soon as you remember unless it is close to your next scheduled dose. Do not double the dose to make up for a missed one. Contact your healthcare provider for specific guidance.
Can I exercise during the test period?
You should avoid strenuous exercise during the 24-hour urine collection period, as intense physical activity can affect cortisol levels and potentially alter test results. Light activities such as walking are generally acceptable.
How long does it take to get results?
Results are typically available within a few days to a week, depending on the laboratory. Your doctor will contact you with the results or discuss them at your follow-up appointment.
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy