Home Biomarkers Cortisol Serum (p.m)

Cortisol Serum (p.m)

Hormones Biomarker

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Collection Type: Blood

Body System

Related System: Hormones

Overview

Cortisol (serum, p.m.) measures the blood level of cortisol in the evening, when healthy people normally have low concentrations because cortisol follows a strong diurnal (day–night) rhythm driven by ACTH from the pituitary. The evening (late‑day/bedtime) value is used to detect loss of normal nightly suppression a hallmark of Cushing’s syndrome and to help evaluate adrenal insufficiency. Symptoms prompting testing include unexplained weight change, muscle weakness, easy bruising, hypertension, mood changes, fatigue, fainting or salt craving. Results vary with age, pregnancy, sex hormones or oral contraceptives (which raise total cortisol), obesity, acute illness, sleep pattern, and recent steroid use; pediatric and elderly reference ranges differ.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: Hormones - Symptoms: weight gain or loss, fatigue, muscle weakness, high blood pressure, mood disturbances, easy bruising, hyperpigmentation, salt craving - Diagnoses/monitoring: Cushing’s syndrome/disease, adrenal insufficiency (primary or secondary), effect of exogenous glucocorticoids, monitoring ACTH therapy or pituitary/adrenal disorders - Reasons for abnormal levels: pituitary or adrenal tumors, exogenous steroids, stress/acute illness, depression, pregnancy, altered cortisol-binding globulin - Biological meaning: high evening cortisol suggests loss of diurnal control (excess cortisol); low evening cortisol may indicate adrenal failure or suppression - Lifestyle/family: shift work, poor sleep, heavy exercise, alcohol, smoking, family history of endocrine tumors or congenital adrenal disorders

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Understanding Test Results

Evening cortisol >10 μg/dL (above the normal p.m.
range) suggests loss of normal nighttime suppression and raises concern for Cushing’s syndrome; values >15–20 μg/dL make Cushing’s more likely and warrant confirmatory testing (overnight dexamethasone suppression, 24‑hour urine free cortisol, late‑night salivary cortisol, imaging).
Mild elevations (≈10–15 μg/dL) can result from stress, acute illness, depression, pregnancy or drugs (OCPs, estrogens).
Evening cortisol <3 μg/dL suggests possible adrenal insufficiency; very low values or a cortisol <1.8 μg/dL after ACTH stimulation indicate adrenal failure (primary or secondary) and require prompt evaluation.
Interpret results with sampling time, concurrent medications, and CBG/albumin status in mind.

Normal Range

3-10 μg/dL OR 83-276 nmol/L

FAQs

Q: What is a cortisol PM test?

A: A cortisol PM test measures cortisol levels in the evening—often via late-night saliva or blood—to assess the hormone’s normal daily decline. It evaluates adrenal function, screens for conditions like Cushing’s (elevated late-night cortisol) or adrenal insufficiency (abnormally low levels), and helps monitor treatment. Collection timing is crucial (commonly around 11 p.m.); results are interpreted with clinical context and other tests.

Q: What is a good PM cortisol level?

A: Good PM cortisol depends on timing and the lab’s reference. For late afternoon/evening (about 4–8 PM) a healthy serum cortisol is generally low—typically below about 5 µg/dL (≈140 nmol/L). A late‑night/midnight serum cortisol used to screen for Cushing’s is usually expected to be <1.8 µg/dL (≈50 nmol/L). Discuss results with your clinician.

Q: What does high PM cortisol mean?

A: High evening (PM) cortisol means the normal day–night rhythm is blunted: cortisol remains elevated when it should be low. Causes include chronic stress, Cushing’s syndrome or exogenous steroid use, shift work, depression, or disrupted sleep. Persistently high nighttime cortisol is linked to poor sleep, impaired immunity, weight gain, high blood pressure, insulin resistance and greater long-term metabolic and cardiovascular risk; medical evaluation is advised.

Q: What is the cortisol serum used for?

A: The serum cortisol test measures blood cortisol to assess adrenal and pituitary function. It helps diagnose and monitor conditions such as Cushing’s syndrome, Addison’s disease, adrenal insufficiency, and pituitary disorders, and evaluates unexplained fatigue, weight change, blood pressure or glucose abnormalities, and abnormal hair growth. Results depend on timing (morning vs evening) and may require repeat, stimulation, or suppression tests for confirmation.

Q: What are high cortisol symptoms?

A: High cortisol can cause weight gain—especially around the abdomen and face—moon face and a fatty hump between the shoulders, thinning skin, easy bruising and purple stretch marks. It often leads to muscle weakness, high blood pressure and blood sugar, mood changes (anxiety, depression, irritability), sleep disturbances, low libido or menstrual irregularities, increased infections, and persistent fatigue.

Q: What is the difference between cortisol AM and PM?

A: Cortisol follows a diurnal rhythm: levels peak in the early morning (cortisol awakening response) to boost alertness, blood glucose and blood pressure, then fall through the day to reach a low at night to permit sleep and recovery. Abnormally high nighttime cortisol or a blunted morning peak can indicate stress, sleep disorders, or adrenal dysfunction and may warrant medical evaluation.