Quick Facts
- Sample: Blood draw from arm vein
- Fasting: No fasting required
- Turn-around: 1-2 business days. May take longer based on weather, holiday, or lab delays.
Benefits
- Detect Cushing's syndrome early with 96% accuracy when cortisol timing is right
- Skip insurance hassles and get results without physician referrals or pre-approval
- Convenient afternoon scheduling that fits your work schedule—no fasting needed
- Monitor stress hormone patterns to understand chronic fatigue and mood changes
- Clinical-grade precision using advanced immunoassay technology for reliable results
Who Is This Test For?
- People experiencing chronic fatigue or unexplained energy crashes
- Individuals with mood disorders like depression or anxiety symptoms
- Those with unexplained weight changes or difficulty losing weight
- People with high blood pressure or diabetes at younger ages
- Individuals taking corticosteroid medications long-term
- Anyone with family history of endocrine or adrenal disorders
How It Works – Just 3 Steps
- Schedule your test between 3:00-6:00 PM for accurate circadian timing
- Simple blood draw at any Walk-In Lab location—takes just minutes
- Get secure results online within 1-2 business days with reference ranges
FAQ
What makes PM cortisol testing different from morning tests? PM testing captures cortisol's natural decline, essential for diagnosing Cushing's syndrome and evaluating your body's stress hormone rhythm.
Do I need to prepare for this test? No fasting required. Avoid prednisone for 72 hours and note any birth control or hormone medications you're taking.
What if my results are abnormal? Elevated PM levels may indicate Cushing's syndrome, while low levels could suggest adrenal insufficiency. Follow up with an endocrinologist for interpretation.
Can stress affect my results? Yes, chronic stress can elevate cortisol. Try to schedule during a typical day and avoid major stressors before testing.
Is the timing really that important? Absolutely. Cortisol follows a circadian rhythm—testing between 3:00-6:00 PM ensures accurate assessment of your hormone cycle.
How accurate is this test? PM cortisol testing achieves 96% sensitivity and 100% specificity for Cushing's syndrome diagnosis when properly timed (Journal of Clinical Endocrinology & Metabolism).
More Details
What is the purpose of this test?
The Cortisol Blood Test, PM measures cortisol hormone levels during late afternoon hours when concentrations naturally decline from their morning peak. This test evaluates your adrenal glands' normal circadian rhythm, which is crucial for diagnosing disorders like Cushing's syndrome and Addison's disease (Endocrine Society Clinical Practice Guidelines).
Cortisol helps regulate metabolism, immune response, and stress reaction throughout your body. By measuring afternoon levels, healthcare providers can assess whether your hypothalamic-pituitary-adrenal (HPA) axis functions properly and maintains healthy hormone patterns.
Who would benefit from this test?
This test serves individuals experiencing symptoms that may indicate cortisol imbalance. Primary candidates include people with chronic fatigue, unexplained weight changes, mood disorders, or suspected hormonal imbalances. The test is particularly valuable for those with risk factors including prolonged corticosteroid use, unexplained hypertension, or family history of endocrine disorders.
Health-conscious consumers using direct-to-consumer lab services benefit from accessible hormonal assessment without requiring physician referrals. This enables proactive health monitoring and provides concrete data for subsequent medical consultations.
When should I order a Cortisol Blood Test, PM?
Order this test when experiencing symptoms of hormonal imbalance, as follow-up to abnormal morning cortisol results, or when screening for Cushing's syndrome. The test must be drawn between 3:00-6:00 PM for accurate results due to cortisol's circadian rhythm (Mayo Clinic).
Consider testing if you have persistent symptoms like muscle weakness, mood changes, sleep problems, or unexplained metabolic disruptions that haven't responded to other treatments.
How do I interpret the results?
- 2.3-11.9 μg/dL: Normal circadian rhythm – Continue routine monitoring.
- Above 11.9 μg/dL: Possible Cushing's syndrome – Endocrinologist consultation needed.
- Below 2.3 μg/dL: Possible adrenal insufficiency – Further testing recommended.
- Above 7.5 μg/dL (evening): High suspicion for Cushing's – Immediate specialist referral.
Recent studies show U.S. Cushing's syndrome incidence is 48.6 cases per million annually—much higher than previously estimated.
Results should always be interpreted alongside symptoms, medications, and stress levels. Multiple measurements may be necessary for definitive diagnosis.
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 PM cortisol testing. Schedule your blood draw specifically between 3:00-6:00 PM to capture the natural circadian decline in cortisol levels. Avoid prednisone or prednisolone therapy for at least 72 hours prior to testing due to cross-reactivity.
Discontinue biotin supplements at least 72 hours before collection. Women should note if taking contraceptives, hormone replacement therapy, or if pregnant, as these can elevate cortisol concentrations.
How often should I get tested?
- Routine health monitoring: Annually with physical exam
- Abnormal results (first occurrence): Repeat in 2-4 weeks
- Monitoring treatment response: Every 3-6 months as directed
- Chronic stress management: Every 6-12 months
- High-risk individuals: Every 6 months initially
If results are normal but symptoms persist, consider repeat testing in 6 months or evaluation for cyclical hypercortisolism.
Why early detection matters
Early detection of cortisol disorders prevents serious complications and improves treatment outcomes. Untreated Cushing's syndrome can lead to diabetes, cardiovascular disease, and bone loss. Conversely, undiagnosed adrenal insufficiency can result in life-threatening adrenal crisis.
Cushing's disease predominantly affects women (3:1 ratio) between ages 20-50, with an estimated prevalence of 22 cases per million (Clinical Research Studies). Timely diagnosis enables appropriate treatment and prevents long-term health consequences.
Related tests you may consider
Cortisol AM Blood Test provides morning cortisol levels for complete diurnal pattern assessment. The AM/PM combination offers comprehensive insight into HPA axis function and enhances diagnostic accuracy for adrenal disorders.
Cortisol Urine Test, Urinary Free, 24-Hour measures total cortisol production over a complete day, offering broader perspective on overall cortisol output. This test complements PM cortisol by providing integrated assessment of cortisol production patterns.
Adrenocorticotropic Hormone (ACTH) Blood Test determines whether abnormal cortisol levels originate from pituitary or adrenal gland dysfunction. When paired with PM cortisol, ACTH testing helps differentiate between primary and secondary adrenal insufficiency.
