Cortisol test: which test answers which question

A cortisol test measures a hormone made by your adrenal glands. Cortisol helps with your stress response, inflammation, blood sugar, metabolism and blood pressure. Most people who search for a cortisol test mean a blood test: a quick draw from a vein, usually timed for the morning.

What the number means depends on when the sample was taken, what you were doing, what medicines you take and which lab ran it. That makes a cortisol test a useful piece of a work-up. It is not an answer by itself, and this guide is built around that.

Cortisol

One blood draw for one cortisol result. It can’t diagnose or rule out an adrenal condition by itself.

$109

See this test at HealthLabs

Price checked November 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.

Which test fits which question

Match the test to the question you are actually asking. Several of these tests are not interchangeable.

Your question	Test that usually fits	Who usually arranges it
Is my cortisol low? I have long-lasting tiredness, weak muscles, weight loss or loss of appetite.	A morning blood cortisol, often with an ACTH level. An unclear result leads to a stimulation test. See low cortisol.	A clinician
Is it too high? I bruise easily, have wide purple stretch marks or a rounded face.	Usually two of: a late-night saliva test, a 24-hour urine collection, a low-dose dexamethasone suppression test. See high cortisol.	A clinician
Does my cortisol fall through the day the way it should?	Blood samples in the morning and the afternoon, or saliva samples at set times.	You or a clinician
Is stress or “adrenal fatigue” behind how I feel?	No cortisol test answers this. See adrenal fatigue.	Not applicable
I’m tired and don’t know why.	Cortisol is one possibility among several. See tests for tiredness.	A clinician, or you

The symptoms in the first two rows are the ones MedlinePlus lists for too little and too much cortisol. Having one of them doesn’t mean you have either condition. Each also has other causes.

What a cortisol blood test measures

A standard cortisol blood test measures cortisol in serum, the liquid part of blood. That is usually a total cortisol figure. About 90% of the cortisol in blood is attached to a carrier protein called CBG. Only about 5% is free cortisol, the part that is active (Endocrine Reviews, 2024).

This matters because anything that changes the carrier protein changes total cortisol without changing free cortisol:

• Oral estrogen raises CBG, and so raises total cortisol. So does pregnancy.
• Low carrier protein, as in some kidney disease, or low albumin in critical illness, can push total cortisol down.

The seller’s page for its single cortisol test doesn’t say whether it reports total or free cortisol. If that matters for your question, check before you order. Our page on free and total cortisol goes further.

When to have it

Cortisol follows a daily rhythm. It peaks in the early morning, around 7 to 8 a.m. in one review (Int J Mol Sci, 2025), falls through the day and reaches its lowest point at around midnight (Endocrine Reviews, 2024).

Because of that rhythm, a value only means something next to its time. MedlinePlus says blood samples are typically taken twice on the same day, in the morning when levels are highest and around 4 p.m. when they are usually much lower. Our page on AM and PM timing covers the practical side.

One published range for total serum cortisol in blood. Other labs and methods give different figures, so use the range printed on your report:

Source	Morning	Afternoon
Review in Int J Mol Sci (2025), for total serum cortisol	3 to 23 µg/dL at 8 a.m.	3 to 13 µg/dL at 4 p.m.

Labs differ because assays differ. Each lab sets its own performance, and in one study five automated immunoassays read 1.08 to 1.36 times higher than a mass spectrometry method (Endocrine Reviews, 2024). Use the range printed on your own report. If your report is in nmol/L, the cortisol units converter helps you compare. The normal range page has more.

One draw, or a morning and later pair

A single draw gives one value. If nobody notes the time, you can’t tell whether it is high or low for that time of day. The seller’s own page for its single cortisol test says as much: it notes that cortisol changes with time of day and other factors, which makes a single value hard to interpret, and that further testing is needed to judge too much or too little cortisol.

A morning and later pair shows both ends of the day. That helps when the question is about the daily pattern. The seller’s page for its morning-and-later test is unclear about when the second sample is taken and doesn’t say whether it is one visit or two. Confirm that before you order, and follow the timing on your lab order.

Neither seller page states a fasting rule. Follow the instructions on your lab order. MedlinePlus doesn’t list fasting for a cortisol blood test, though it does say fasting may be needed for ACTH.

Other tests you may hear about

• 24-hour urine. You collect all urine for a day. NIDDK lists this as a test for Cushing’s syndrome. A review notes it can be affected by high fluid intake and kidney function, and that two collections are recommended.
• Late-night saliva. Saliva is collected in the late evening, when cortisol should be low. It can be done at a provider’s office or at home with a kit, and kits often use a swab held in the mouth for about two minutes. Don’t eat, drink, brush or floss for 30 minutes first.
• Dexamethasone suppression test. You take a low dose of dexamethasone and have blood drawn the next morning. This is arranged and read by a clinician.
• ACTH. ACTH is the pituitary hormone that tells the adrenal glands to make cortisol. It is usually measured with cortisol to help show which gland is involved. See the ACTH blood test.
• ACTH stimulation test. A clinic test for suspected adrenal insufficiency: blood is drawn before and after an injection of synthetic ACTH.
• Hair, dried-urine and wearable tests. The evidence for these is different again. See saliva, urine and hair and wearables.

NIDDK says “no one test is perfect” for Cushing’s syndrome, so doctors usually do two tests to confirm it. The tests that screen for it belong with a clinician.

How to order and prepare

1. Decide who orders it. If you have symptoms that worry you, start with a clinician. They can choose the test that fits what they suspect. A test you order yourself gets you a number faster, but the number still needs to go to a clinician. MedlinePlus says at-home tests are not a replacement for a provider’s guidance, and that you should follow up with your provider whatever the result.
2. Choose the test. One draw suits a simple check. A morning and later pair suits a question about the daily pattern.
3. Read the lab order. It sets the timing and any fasting. Follow it over anything on this page.
4. Rest first. MedlinePlus says stress and exercise can raise cortisol, so rest beforehand.
5. Tell the lab and your clinician what you take. That includes steroid medicines of any kind, skin creams, birth control pills and other oral estrogen, and biotin. Some medicines change cortisol results. Some lab methods can read a steroid medicine as cortisol, and biotin can interfere with certain immunoassays. Don’t stop any medicine to prepare for a test unless your prescriber tells you to.
6. Compare sellers. Prices for the same type of test vary widely between sellers, and it is worth comparing. Our cost and where to buy page explains.

• CortisolOne blood draw, one result $109 See this test at HealthLabs
• Cortisol AM and PMA morning sample and a later one. Check the timing before you order $129 See this test at HealthLabs

Sold by HealthLabs. Prices checked November 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.

Our test finder can help you choose between the two.

What a cortisol test can’t show

• It can’t diagnose or rule out Cushing’s syndrome or adrenal insufficiency. MedlinePlus says a cortisol test alone can’t identify the cause of an abnormal level, and that more testing is usually needed. A laboratory review says random (untimed) samples are of no use for assessing Cushing’s syndrome, which needs timed samples or a dynamic test.
• It can’t say why a level is high or low. MedlinePlus lists steroid medicine or stopping it suddenly, stress, pregnancy, exercise, temperature extremes and some medicines, such as birth control pills, as common reasons for an abnormal result that are not a disease.
• It can’t measure “stress” or “adrenal fatigue”. A 2024 paper in the Journal of the Endocrine Society states that adrenal fatigue has never been scientifically proven to exist. It says the symptom scores and salivary cortisol profiles sold for it have never been validated, and that the accepted tests (serum cortisol, ACTH and the ACTH stimulation test) are usually normal in people given the label.
• It can’t be compared across labs without care. Reference ranges and cut-offs depend on the method used.
• It doesn’t replace a clinician. A result is information to take to one.

What happens next

A result outside the range. This is a reason to talk to a clinician, not a diagnosis. They may repeat the test, add ACTH, or order the tests for Cushing’s syndrome or adrenal insufficiency described above. A 2026 study of morning cortisol in pituitary-related (central) adrenal insufficiency says stimulation testing is recommended when a morning value is neither clearly low nor clearly sufficient. See testing for high cortisol and testing for low cortisol.

A result inside the range, with symptoms that continue. Keep going. For Cushing’s syndrome, NIDDK says no one test is perfect, and symptoms like fatigue can have many causes. Ask a clinician what else to check. Our page on routine blood work and cortisol covers what ordinary panels do and don’t include.

If you take a steroid medicine. Ask your prescriber how it affects the test and what to do. Don’t stop or change the medicine yourself. Prednisone and cortisol has more.

If you are very unwell. Vomiting, severe weakness or fainting are not reasons to order a test. They are reasons to seek urgent care. See low cortisol for the signs to watch for.

Questions people ask

Can you test cortisol at home?

Yes, in one form. MedlinePlus says saliva samples can be collected at home with a kit, and several samples may be taken at different times. Many home kits are mailed to a lab. MedlinePlus advises using only tests the FDA has approved or authorized and following the directions closely, since even minor changes can affect results. See at-home or lab test.

What is a cortisol blood test called?

Lab menus use several names: cortisol, serum cortisol, morning (AM) cortisol, total cortisol and free cortisol. The free version is a different measurement from the total. See cortisol test names.

Keep reading

• Low cortisol

  Causes, symptoms, emergency signs and how it is tested.

• High cortisol

  What high cortisol can mean and how it is worked up.

• AM and PM timing

  When the samples are taken and why timing matters.

• Normal cortisol levels

  Published ranges by time of day, with sources.

• ACTH blood test

  The hormone that signals the adrenal glands.

• Cost and where to buy

  Why prices vary and what to compare.