Pre-Dose Dexamethasone Blood Test
A blood test that measures the level of 17-hydroxyprogesterone, a hormone intermediate, to help diagnose and monitor conditions like Congenital Adrenal Hyperplasia (CAH).
{"This test measures 17-hydroxyprogesterone hormone levels in your blood","It helps diagnose Congenital Adrenal Hyperplasia (CAH) and other adrenal disorders","The 'pre dose dexamethasone' means your blood sample was taken BEFORE you received dexamethasone medication","A small blood sample will be taken from a vein in your arm","Results help your doctor plan appropriate treatment if needed"}
Key facts at a glance
- LOINC
- 57546-4
- Short code
- 17-OHP
- Synonyms
- 17OHP Pre Dex SerPl-sCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or plain red top tube
- Units
- N/A
- Ref low
- 0.6
- Ref high
- 4
- Critical range
- — – 30 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Chemiluminescent Immunoassay (CLIA)
- CPT
- 83001
- SNOMED
- 31316001
- Specimen volume
- 1.0-2.0 mL serum minimum
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 30 days. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 50
- Lipemia max
- 100
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
This blood test measures the amount of dexamethasone, a man-made corticosteroid medicine, in your blood right before you take your next scheduled dose. It shows how much of the medicine is circulating in your body and helps your doctor judge whether your current dosing schedule is working as intended.
The 17-Hydroxyprogesterone (17-OHP) test measures the amount of a hormone called 17-hydroxyprogesterone in your blood. This hormone is produced by your adrenal glands, which sit on top of your kidneys. 17-OHP is an intermediate product in the process of making cortisol, an important stress hormone. When there is a problem with cortisol production, 17-OHP levels can become abnormally high.
"Pre dose" simply means the blood sample is drawn immediately before you take your dexamethasone dose. At that moment, the level in your blood reflects how much medicine remains from your previous doses, which tells your doctor how well the medicine is being absorbed and cleared from your body.
The phrase 'pre dose dexamethasone' means that your blood sample was taken BEFORE you received a dose of dexamethasone medication. Dexamethasone is a corticosteroid medication sometimes used to suppress excess hormone production. By taking the blood sample before giving the medication, your doctor can see your natural baseline 17-OHP level. This helps them understand how your body responds and plan the right treatment for you.
Your doctor may order this test if you are taking dexamethasone for a hormone problem, inflammation, or as part of an evaluation for conditions such as Cushing syndrome, or if your cortisol results did not come back as expected. It can confirm that you are absorbing the medicine properly and help your doctor adjust your dose safely.
Your doctor may order this test if they suspect you have a disorder affecting your adrenal glands, particularly Congenital Adrenal Hyperplasia (CAH). CAH is a genetic condition that affects how the adrenal glands produce hormones. Symptoms in babies may include ambiguous genitalia, early puberty, or salt-wasting crises. Older children and adults may experience early puberty, irregular periods, excessive hair growth, or fertility problems. This test is also used to monitor how well treatment is working.
The test is done with a simple blood draw. A healthcare professional will clean your skin, insert a small needle into a vein in your arm, and collect a sample into a tube. The sample is taken just before your next dose of dexamethasone, and the draw itself usually takes only a few minutes.
A healthcare professional will draw a small amount of blood from a vein in your arm using a needle. The procedure only takes a few minutes and may cause brief discomfort or a small bruise at the injection site. The blood sample is then sent to a laboratory for analysis. You may need to fast (not eat or drink except water) for a certain period before the test—your doctor will tell you if this is necessary.
Your results show how much dexamethasone is present in your blood just before the next dose. A level within the expected range suggests the medicine is being absorbed and cleared normally. A low level may mean the medicine is not being absorbed well or doses were missed, while a high level may suggest it is building up in your body. Your doctor will interpret your numbers together with your symptoms and other test results.
Normal 17-OHP levels vary by age, sex, and whether you are pregnant. High levels of 17-OHP typically suggest Congenital Adrenal Hyperplasia or other adrenal gland disorders. Your doctor will interpret your results based on your specific situation, symptoms, and other test results. If your levels are abnormal, follow-up testing may be needed to confirm a diagnosis and determine the best treatment approach.
Reference range
Adults (pre-dose dexamethasone): 0.6-4.0 nmol/L; Children: Age-dependent reference ranges apply; Neonates: Higher normal ranges expectedN/A
Sample collected before dexamethasone administration. Patient should fast overnight (8-12 hours). Morning collection preferred (typically 8 AM). Inform patient about the dexamethasone suppression test protocol. Continue medications as directed by physician unless instructed otherwise.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The 17-OHP test is primarily used to diagnose and monitor Congenital Adrenal Hyperplasia (CAH), a group of genetic disorders affecting adrenal hormone production. Early diagnosis of CAH is important because untreated cases can lead to serious problems including salt imbalance, dehydration, and accelerated growth in children followed by short adult height. In newborn screening, elevated 17-OHP can identify babies with CAH before symptoms become severe.
The pre-dose dexamethasone measurement helps establish a baseline before treatment begins. By comparing 17-OHP levels before and after dexamethasone treatment, doctors can assess how effectively the medication is suppressing excess hormone production. This information guides dosing decisions and helps optimize treatment outcomes for patients with adrenal disorders.
Frequently asked questions
Is fasting required before the test?
Are there any risks with this blood test?
How long does it take to get results?
Can medications affect my 17-OHP results?
What happens if my 17-OHP level is high?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
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 10, 2026. · Read our editorial policy