• What is the clinical purpose of the evening cortisol test?

The goal is to identify a loss in the normal daily decline of cortisol levels, which is a characteristic feature of Cushing’s syndrome.

• How is this test used as part of a dexamethasone suppression test?

In this test, evening cortisol is measured after a dose of dexamethasone; if the cortisol level remains elevated, it supports a diagnosis of Cushing’s syndrome.

• Is fasting required for the evening serum cortisol test?

No, fasting is not required before your evening serum cortisol levels are measured.

Medical Laboratories

Evening Serum Cortisol Test

Evening Serum Cortisol Test (PM)

Analyze evening cortisol levels to monitor your daily hormonal balance, helping detect adrenal gland disorders and ensuring healthy sleep quality and proper physical relaxation patterns.

Trusted medical contentUpdated: 04-09-2026Views: 46LHL-3076

About this service

A quantitative test that measures cortisol hormone levels in blood serum, taken in the late afternoon or evening, usually between 4 and 6 PM (and up to 8 PM). The goal is to assess the normal decline phase in the daily cortisol rhythm. In healthy individuals, cortisol levels significantly decrease by evening. This measurement is often used in conjunction with a morning measurement to evaluate the full daily rhythm or as part of dexamethasone suppression tests.

Purpose Test

Detecting loss of normal diurnal cortisol rhythm: A hallmark of Cushing’s syndrome, where cortisol fails to decrease adequately in the evening.
Use in the dexamethasone suppression test: After an evening dose of dexamethasone, evening cortisol is measured. Persistent elevation supports Cushing’s diagnosis.
Assessing the full HPA axis: Useful for evaluating the hypothalamic-pituitary-adrenal axis when rhythm disorders are suspected.
Monitoring effects of chronic stress: Severe chronic stress can alter normal cortisol patterns; evening measurement helps detect this impact.

Recommended groups

Patients suspected of Cushing’s syndrome, especially those with elevated or borderline morning cortisol.
Patients showing clinical signs of cortisol excess, such as central obesity, moon face, or high blood pressure.
Patients with known pituitary or adrenal tumors.
Occasionally, it is used to assess sleep disturbances related to chronic psychological stress.

Normal Levels

Evening (4-6 PM): approximately 3-10 micrograms per deciliter (µg/dL).
Midnight (10 PM - 12 AM): < 1.8 micrograms per deciliter (µg/dL) or < 50 nanomoles per liter (nmol/L) is the important cutoff.
Normal (low) evening: indicates a healthy daily rhythm.
Elevated evening (>50% of the morning value or > 1.8 µg/dL at night): indicates loss of normal physiological suppression, which is an important sign of Cushing’s syndrome.

Conditions and notices

Fasting is not required

• The timing of the sample is precise and critical. The sample must be drawn at the exact scheduled time by the physician (e.g., 4 PM, 6 PM, 11 PM). Accurate recording of the time on the tube is essential.

• The patient should be rested and calm for at least one hour before sample collection, as acute stress can elevate cortisol levels.

• The physician and laboratory should be informed of the patient’s usual sleep/wake schedule.

• They should be informed of all medications, especially steroids or psychiatric drugs.

• The sample is collected in a serum tube (red or yellow cap).

Frequently Asked Questions

Short answers to the FAQs published with this service.

What is the normal evening cortisol level?

The normal range varies, but it is usually less than 50% of the morning value. More specifically, it is often below 3-7 micrograms per deciliter (µg/dL) or 83-193 nanomoles per liter (nmol/L) by 10 PM. A level above 1.8 µg/dL (50 nmol/L) at midnight is considered abnormal and indicates loss of normal suppression.

Why is this test requested along with the morning measurement?

Diagnosis depends on the secretion pattern, not a single reading. In Cushing’s syndrome: Morning cortisol may be elevated or normal. Evening/night cortisol is abnormally high because it fails to decrease. Comparing the two readings reveals the disruption in the daily rhythm.

Can my sleep pattern affect this test result?

Yes, significantly. If you work night shifts and sleep during the day, your daily cortisol rhythm is reversed. In this case, cortisol may be naturally high in your “evening” (your wake time). Therefore, it is very important to inform your doctor if you have an irregular sleep schedule. The sample should be taken at your personal “evening” time.

Evening Serum Cortisol Test

About this service

Purpose Test

Recommended groups

Symptoms indicative

Normal Levels

What is included?

Conditions and notices

Frequently Asked Questions

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