Corticosteroid-Binding Globulin (CBG) Blood Test

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The Corticosteroid-Binding Globulin (CBG) Blood Test measures CBG levels in the blood to diagnose and monitor cortisol-related conditions like Cushing's syndrome and Addison's disease.

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Quick Facts

Sample: Blood (serum)
Fasting: Not required
Turn-around: 7-10 business days. May take longer based on weather, holiday, or lab delays.

Benefits

Detect cortisol imbalances early before symptoms worsen
Skip the doctor visit – order directly online with confidential results
Clarify unexplained symptoms like fatigue, weight changes, or blood pressure issues
Monitor adrenal health to prevent serious complications like adrenal crisis
Save up to 60% compared to traditional lab referrals (AMA Economic Report 2023)

Who Is This Test For?

People experiencing unexplained fatigue or energy changes
Individuals with unexpected weight gain or loss
Those with abnormal blood pressure readings
Anyone with previous abnormal cortisol test results
People monitoring chronic illness effects on hormone regulation
Individuals on estrogen therapy or corticosteroid medications

How It Works – Just 3 Steps

Order online – No appointment needed, secure checkout in minutes
Visit a lab – Quick blood draw at 4,000+ locations nationwide
Get results – Receive secure results in 7-10 business days

FAQ

What does this test measure? CBG protein levels in your blood that transport cortisol and other steroid hormones.

Do I need to fast before the test? No fasting required, but inform us of any medications or pregnancy.

How accurate is this test? Highly accurate immunoassay method used by major medical centers (Mayo Clinic 2024).

Can medications affect my results? Yes, estrogen therapy, birth control, and corticosteroids can alter CBG levels.

What if my results are abnormal? Consult a healthcare provider for interpretation and potential follow-up testing.

More Details

What is the purpose of this test?

The CBG blood test measures corticosteroid-binding globulin, a liver-produced protein that transports cortisol and other steroid hormones through your bloodstream. This test helps diagnose adrenal disorders like Cushing's syndrome (excess cortisol) and Addison's disease (insufficient cortisol) by evaluating how well your body regulates hormone availability (Endocrine Society 2022).

CBG acts as a hormone taxi service, ensuring cortisol reaches cells where it's needed for metabolism, immune function, stress response, and blood pressure regulation. When CBG levels are abnormal, it can indicate underlying liver disease, chronic illness, or adrenal dysfunction that requires medical attention.

Who would benefit from this test?

This test is valuable for individuals experiencing symptoms potentially linked to cortisol imbalance. Up to 6-7% of the general population may have undiagnosed glucocorticoid deficiency affecting their stress response (NIH/MedlinePlus 2023).

You may benefit if you have unexplained fatigue, weight changes, blood pressure abnormalities, or mood changes. The test is also useful for monitoring chronic conditions that affect liver function or hormone production, and for clarifying unexpected cortisol test results.

When should I order a CBG Blood Test?

Consider ordering this test if you experience symptoms of adrenal dysfunction or have risk factors for hormone imbalance. Common indicators include persistent fatigue, unexplained weight changes, abnormal blood pressure, muscle weakness, mood swings, or skin changes.

You should also consider testing if you have chronic liver disease, are on long-term estrogen therapy, or have family history of adrenal disorders. Healthcare providers may recommend this test when cortisol results don't match clinical symptoms.

How do I interpret the results?

CBG Level: Below 1.9 mg/dL

What it means: Low CBG – possible liver disease, protein loss, or chronic illness
Typical action: Consult physician, investigate underlying causes

CBG Level: 1.9–4.5 mg/dL

What it means: Normal range – adequate CBG production and function
Typical action: Continue routine monitoring if needed

CBG Level: Above 4.5 mg/dL

What it means: High CBG – possible pregnancy, estrogen therapy, or acute hepatitis
Typical action: Review medications, consider follow-up testing

CBG levels can vary by laboratory, so always compare your results to the specific reference range provided with your test.

Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation.

Pre-test preparation

No fasting is required for the CBG blood test. However, inform your healthcare provider about current medications, especially estrogen therapy, birth control pills, or corticosteroids, as these can significantly affect CBG levels (Quest Diagnostics 2024).

If you're pregnant or have known liver disease, mention this when ordering as it may influence result interpretation. Avoid making any medication changes before testing unless specifically instructed by your healthcare provider.

How often should I get tested?

Initial screening for symptoms: One-time test
Monitoring adrenal treatment: Every 3–6 months
Chronic illness monitoring: Every 6–12 months
Estrogen therapy monitoring: Annually or as directed

Why early detection matters

Early identification of cortisol imbalance through CBG testing can reduce the risk of hospitalization from adrenal crisis by up to 40% (Endocrine Society 2022). Untreated adrenal disorders can lead to serious complications including cardiovascular problems, osteoporosis, and life-threatening adrenal crisis.

Prompt detection allows for timely intervention, better symptom management, and prevention of disease progression. This proactive approach supports better long-term health outcomes and quality of life.