Understanding Your Medical Test: A Complete Patient Guide to Testing, Procedures, and Interpreting Your Results
This blood test measures 17-hydroxyprogesterone levels one day after taking dexamethasone to monitor treatment effectiveness for congenital adrenal hyperplasia.
{"Measures hormone levels to check if CAH treatment is working properly","Involves taking a blood sample one day after taking dexamethasone medication","Helps doctors adjust medication doses to prevent complications"}
Key facts at a glance
- LOINC
- 57547-2
- Short code
- 17-OHP-Dex
- Synonyms
- 17OHP 1D p Dex SerPl-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or plain red top tube
- Units
- N/A
- Ref low
- 0.2
- Ref high
- 1
- Critical range
- 0.2 N/A – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Immunoassay (Chemiluminescence or ELISA)
- CPT
- 83498
- SNOMED
- 27018006
- 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
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
What is this test? This test is a laboratory evaluation that your healthcare provider orders to measure specific substances or markers in your body. The results offer a snapshot of how well certain organs and systems are working and help guide important decisions about your ongoing medical care.
This test measures the amount of 17-hydroxyprogesterone (17-OHP) in your blood. 17-OHP is a hormone produced by the adrenal glands. The blood sample is collected exactly one day after you take a dose of dexamethasone, which is a medication that helps suppress excess hormone production.
Why do I need this test? Your doctor may recommend this test to help diagnose a medical condition, monitor an existing illness, check how well a current treatment is working, or screen for potential health problems before any symptoms appear.
This test is primarily used to monitor treatment for congenital adrenal hyperplasia (CAH), a genetic condition that affects the adrenal glands' ability to produce hormones. If you are being treated with dexamethasone for CAH, this test helps your doctor check whether the medication is working effectively to control hormone levels and prevent symptoms like early puberty, excess hair growth, or irregular periods.
How is the test performed? The procedure depends on the type of test ordered. Most tests require a small blood sample drawn from a vein in your arm, while others may use a urine, saliva, or tissue sample. A trained technologist collects the sample and sends it to a laboratory for analysis. The process is usually quick, and you can typically return to normal activities right away.
A healthcare professional will draw a small blood sample from a vein in your arm, usually in the morning. It is important that you take your dexamethasone dose exactly as instructed by your doctor, and the blood draw must occur exactly one day after that dose for accurate results. The blood sample is then sent to a laboratory for analysis.
What do the results mean? Your results are compared with established reference ranges to show whether your values are normal, high, or low. Abnormal findings do not always indicate a serious problem, since medications, diet, and recent activity can influence results. Your healthcare provider will explain what your values mean and discuss any follow-up testing or treatment that may be needed.
Your doctor will interpret your results based on your age, sex, and specific condition. Well-controlled CAH typically shows low 17-OHP levels after dexamethasone suppression. High levels may indicate that your current treatment dose needs adjustment. Your healthcare provider will discuss your specific results and any necessary changes to your treatment plan.
Reference range
Normal suppression: <1.0 ng/dL (0.03 nmol/L); Equivocal: 1.0-5.0 ng/dL; Incomplete suppression: >5.0 ng/dL (indicates adrenal hyperplasia or Cushing's disease)N/A
Patient receives 1mg dexamethasone orally at 11 PM the night before blood draw. Blood sample collected at 8 AM the following morning (1 day post dose). Do not collect if patient has taken glucocorticoids within 2 weeks. Inform laboratory of any medications affecting steroid metabolism.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Frequently asked questions
Do I need to fast before this test?
What happens if I forget to take my dexamethasone dose?
How often do I need this test?
Are there any risks from the blood test?
Can this test diagnose CAH?
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