About the Cortisol, AM & PM Test
Purpose of the Test
This test checks whether your adrenal glands and pituitary gland are making cortisol at the right levels and at the right times of day. A single cortisol reading shows where you are at one moment. It doesn’t show whether your levels follow a normal daily curve.
The clinical value is in the pattern. Cortisol should be highest in the morning and drop significantly by afternoon. When that decline is blunted or absent, it’s a diagnostic signal, even if both values look normal on paper.
The test helps evaluate Cushing’s syndrome, a disorder that causes high cortisol levels, and Addison disease, a condition that causes low cortisol levels. Cortisol testing is also used to monitor treatment for these conditions. It also helps your provider figure out where a problem starts: the adrenal glands, the pituitary gland, or the hypothalamus.
Cortisol affects nearly every organ system in your body and helps regulate several key functions, including blood pressure, blood sugar, immune function, and bone density, according to the Cleveland Clinic. The test serves two purposes:
- Diagnosis: Ordered when symptoms suggest cortisol overproduction or underproduction, such as unexplained weight gain, fatigue, or low blood pressure.
- Monitoring: Used to track treatment response in people with known adrenal or pituitary conditions.
This test doesn’t evaluate stress disorders, anxiety, or burnout. It doesn’t measure adrenocorticotropic hormone (ACTH) directly. It also doesn’t replace a 24-hour urine cortisol test or late-night salivary cortisol test when those are clinically indicated.
What Does the Cortisol, AM & PM Test Measure?
The test measures serum cortisol in two blood samples drawn at specific times of day. Both draws use the same lab method: a serum immunoassay processed at a CLIA-certified lab. The difference between the AM and PM draws is timing, not technique.
“Serum cortisol” means total cortisol in the blood, including both the protein-bound and free fractions. The lab isn’t measuring two different things. It’s measuring the same thing twice to capture the diurnal (daily) cortisol curve.
The panel covers two timed measurements:
- Cortisol, AM (Morning): Measures serum cortisol at peak production, drawn between 7–9 AM when the adrenal glands are most active.
- Cortisol, PM (Afternoon): Measures serum cortisol during the expected daily decline, drawn between 3–5 PM to show how far levels have dropped.
Your provider may choose a different cortisol test based on what they’re looking for:
- 24-hour urine free cortisol: Collects all urine over a full day to measure total cortisol output. Used when Cushing syndrome is suspected.
- Late-night salivary cortisol: A saliva sample collected around 11 PM to midnight, when cortisol should be at its lowest. Helpful when timed blood draws aren’t practical.
- Single serum cortisol (AM only): Captures the morning peak but misses the diurnal pattern entirely.
One note on methodology: cortisol levels can also be affected by certain medicines, such as birth control pills. Oral contraceptives raise cortisol-binding globulin, which pushes total serum cortisol readings higher. That doesn’t mean your adrenal glands are overproducing. It’s a lab measurement effect. Tell your provider if you take them.
When Should I Get a Cortisol, AM & PM Test?
Consider testing if any of these apply:
- Chronic fatigue, weakness, or low energy that doesn’t improve with rest
- Easy bruising or slow wound healing
- High blood pressure that’s hard to control
- Low blood pressure, weight loss, or salt cravings with no clear cause
- Nausea or darkening of the skin (possible signs of adrenal insufficiency)
- Purple or pink stretch marks on the abdomen, thighs, or arms
- Unintentional weight gain, especially around the abdomen and face
- Thin arms and legs, a rounder face, or increased fat at the base of the neck or between the shoulder blades
- A provider who suspects Cushing syndrome, Addison’s disease, or pituitary dysfunction
- Long-term use of corticosteroids such as prednisone, hydrocortisone, or inhaled steroids
How It Works
How to Get Tested
This test is ordered through a healthcare provider, clinic, or hospital lab. CLIA-certified labs process most U.S. cortisol tests.
You’ll visit the lab twice: once in the morning (7–9 AM) and once in the afternoon (3–5 PM). Some labs allow both draws on the same day if you can wait between appointments. Results are typically ready within one to three business days after the lab receives both samples, though timing can vary by lab.
Before the Test
- Schedule your AM draw between 7–9 AM. Arrive rested and avoid intense exercise for at least two hours beforehand. Stress and exercise can raise your cortisol levels, so you may need to rest before your test, according to MedlinePlus. Strenuous activity raises cortisol and will skew your results.
- Schedule your PM draw between 3–5 PM, on the same day or a separate day as your provider directs. Avoid acute stress and strenuous activity before this draw too.
- Tell your provider about all corticosteroid medications. Prednisone, hydrocortisone, inhaled corticosteroids, and topical steroids suppress or mimic cortisol and can significantly affect your readings.
- Tell your provider if you take oral contraceptives. They raise cortisol-binding globulin, which increases total serum cortisol without reflecting true adrenal output.
- Reschedule if you’re acutely ill or injured. Infection and injury spike cortisol and will make your results unreliable.
- Avoid alcohol the day before each draw. No fasting is required.
If you work night shifts, tell your provider before scheduling. Standard AM/PM timing assumes a conventional sleep-wake cycle. Your provider may adjust the draw times to match your personal cortisol peak, which usually occurs 30 to 60 minutes after waking.
During the Test
- Arrive at the lab for your AM draw between 7–9 AM. Bring a photo ID and any order confirmation.
- A phlebotomist draws blood from a vein in your arm. The draw takes a few minutes. You’ll feel a brief pinch.
- A small bandage covers the site. Keep it on for at least 15 minutes.
- Go about your normal day between draws. Don’t take corticosteroid medications between draws unless your provider tells you to. Avoid strenuous exercise, intense stress, and alcohol.
- Return to the lab for your PM draw between 3–5 PM. The procedure is the same.
- A second bandage covers the PM draw site. Keep it on for at least 15 minutes.
Some minor bruising at either site is normal. Call your provider if you notice lasting pain, swelling, or signs of infection.
After the Test
Results are typically ready within one to three business days after the lab receives both samples, though timing can vary by lab. Both the AM and PM values appear on the same report.
Your provider reads them together as a pattern, not as two independent numbers. Don’t try to interpret either value on its own. The relationship between them is what matters.
What Do My Results Mean?
Your report shows two serum cortisol values in micrograms per deciliter (mcg/dL): one from the AM draw and one from the PM draw. Your provider reads both the absolute values and the pattern. Cortisol should be highest in the morning and meaningfully lower by afternoon.
Approximate reference ranges (varies by lab):
| Draw | Reference Range (approximate) |
|---|---|
| AM (7–9 AM) | 6–23 mcg/dL |
| PM (3–5 PM) | 2–11 mcg/dL |
Your lab report will include its own reference range. Use that range, not a general figure, when reviewing results with your provider.
Several factors can affect your readings regardless of what your adrenal glands are doing. Oral contraceptives push AM values higher via cortisol-binding globulin. Acute illness, injury, or stress at the time of either draw can artificially raise cortisol. Night-shift workers may show an inverted or phase-shifted pattern that looks abnormal by clock time but reflects their actual sleep-wake cycle.
If Your Results Are Normal
Both values fall within the reference range and the PM value is meaningfully lower than the AM value. That pattern suggests the adrenal glands and pituitary are producing cortisol on a normal circadian schedule.
A normal result doesn’t rule out every adrenal or pituitary condition. Some early-stage or mild conditions produce values within range. If your symptoms persist, your provider may order an ACTH stimulation test, a 24-hour urine cortisol test, or a late-night salivary cortisol test.
If Your AM Cortisol Is High
An AM value above the reference range may indicate the adrenal glands are producing too much cortisol. Possible causes include:
- Cushing disease: Pituitary tumors that make too much ACTH cause 8 out of 10 cases of Cushing’s syndrome not caused by glucocorticoid medicines, according to the NIDDK. A benign pituitary tumor produces too much ACTH, driving the adrenal glands to overproduce cortisol.
- Ectopic Cushing syndrome: A tumor outside the pituitary produces ACTH.
- Adrenal tumors or hyperplasia: The adrenal glands produce excess cortisol on their own, without a pituitary signal.
- Pseudo-Cushing: Conditions such as severe depression, heavy alcohol use, poorly controlled diabetes, obesity, and anxiety can drive cortisol high enough to mimic a tumor.
Oral contraceptives can push total serum cortisol above the AM reference range without indicating disease. A high AM result alone isn’t a diagnosis. Your provider will order confirmatory testing before drawing conclusions.
If Your AM Cortisol Is Low
An AM value below the reference range may suggest the adrenal glands aren’t producing enough cortisol. Possible causes include:
- Addison’s disease: Primary adrenal insufficiency most often happens when your immune system attacks your adrenal glands, according to the Cleveland Clinic. The adrenal glands are damaged and can’t make enough cortisol on their own.
- Secondary adrenal insufficiency: The pituitary isn’t producing enough ACTH to stimulate the adrenal glands.
- Tertiary (hypothalamic) insufficiency: The hypothalamus fails to produce corticotropin-releasing hormone (CRH), which the pituitary needs to release ACTH. This is frequently caused by prolonged corticosteroid use.
- Long-term corticosteroid use: Prednisone, hydrocortisone, and similar medications suppress the HPA axis over time.
Severely low AM cortisol can be a medical emergency. If your provider suspects acute adrenal crisis, they won’t wait for test results to act.
If Your Diurnal Pattern Is Abnormal
The pattern is abnormal when the PM value doesn’t drop significantly below the AM value, even if both individual values fall within their reference ranges. This is called a flat or blunted cortisol curve.
A flat curve is itself a diagnostic signal. It’s linked to Cushing syndrome and HPA axis dysregulation. This is the key reason a provider orders the Cortisol, AM & PM Test instead of a single AM draw: one draw can’t detect a flat pattern.
Night-shift workers may show an inverted or phase-shifted curve that looks abnormal by clock time. That’s not the same thing. Your provider accounts for your sleep schedule when reading the pattern. An abnormal pattern typically prompts confirmatory testing.