Cortisol levels can be checked through blood, saliva, or urine tests. The right test depends on your symptoms, the time of day, and the health condition your doctor wants to check. These tests can help identify problems linked to cortisol production, including Cushing syndrome and adrenal insufficiency. Your doctor may also recommend more than one test to confirm a diagnosis.
Cortisol is a hormone made by the adrenal glands, which sit above the kidneys. It helps control the body’s response to stress, blood pressure, blood sugar, inflammation, and sleep-wake patterns. Cortisol naturally changes throughout the day, so the timing of a test matters when interpreting the results.
How Do You Test Cortisol Levels?
There are three main ways to test cortisol levels: a blood test, a saliva test, and a 24-hour urine test. Each method measures cortisol differently, and your doctor chooses one based on your symptoms and medical history.
A blood cortisol test measures cortisol in a blood sample, often collected in the morning. A saliva cortisol test measures cortisol in saliva and may be used late at night to check whether levels fall as expected during sleep. A 24-hour urine cortisol test measures the amount of cortisol released in urine over a full day.
One test does not work best for every situation. For example, a doctor investigating possible adrenal insufficiency may use morning blood cortisol and, if needed, an ACTH stimulation test. When Cushing syndrome is suspected, late-night salivary cortisol, 24-hour urinary free cortisol, or a dexamethasone suppression test may be used.
What Are the Different Types of Cortisol Tests?
Blood Cortisol Test
A blood cortisol test is a common way to measure the amount of cortisol in your bloodstream at a particular time. A healthcare professional takes a blood sample from a vein in your arm and sends it to a laboratory for analysis.
The test is often performed in the morning because cortisol levels are usually higher after waking. Depending on the reason for testing, your doctor may request another sample later in the day or order additional tests to understand how your adrenal glands are working.
Blood cortisol testing can help investigate conditions involving low or high cortisol production. However, one result may not provide a full answer because stress, illness, medicines, pregnancy, and other factors can affect cortisol levels.
Saliva Cortisol Test
A saliva cortisol test measures cortisol in a saliva sample. It is often used to check cortisol levels late at night, when levels should normally be low. This makes late-night salivary cortisol useful when a doctor suspects Cushing syndrome.
Depending on the laboratory’s instructions, you may collect saliva at home using a special collection tube or device. You may need to avoid eating, drinking, smoking, brushing your teeth, or using certain oral products for a set period before collecting the sample.
Follow the instructions provided with your test kit. Collecting the sample at the wrong time or allowing blood from irritated gums to mix with saliva may affect the result. Your doctor may request more than one sample because cortisol can vary from day to day.
24-Hour Urine Cortisol Test
A 24-hour urine cortisol test measures the amount of free cortisol excreted in your urine over a full 24-hour period. Unlike a single blood sample, this test gives a picture of cortisol excretion across the day.
To complete the test, you usually empty your bladder at the start time and discard that first sample. After that, collect all urine for the next 24 hours, including the final sample at the end of the collection period. Follow the laboratory’s instructions for storing the container and keeping the sample cool if required.
Missing a urine sample can affect the accuracy of the result. If you forget to collect some urine, contact the laboratory or your healthcare provider to ask whether you need to repeat the test. This test is commonly used when investigating excess cortisol production, including possible Cushing syndrome.
When Should You Get Your Cortisol Levels Tested?
Your doctor may recommend a cortisol test if you have symptoms that suggest your body is making too much or too little cortisol. The test can help investigate problems involving the adrenal glands or pituitary gland, which helps control cortisol production.
Symptoms linked to high cortisol may include unexplained weight gain around the abdomen, a rounder face, easy bruising, wide purple stretch marks, and muscle weakness. These symptoms can occur in people with Cushing syndrome, although other health conditions can cause similar changes.
Low cortisol levels may be linked to ongoing fatigue, muscle weakness, loss of appetite, unexplained weight loss, abdominal pain, and low blood pressure. These symptoms can occur with Addison disease or other forms of adrenal insufficiency. A doctor may recommend testing if several symptoms occur together or if your medical history raises concern about a hormone problem.
MedlinePlus
+1
How to Prepare for a Cortisol Test
Preparation depends on whether you are having a blood, saliva, or urine test. Your healthcare provider or laboratory will explain what you need to do before collecting the sample.
For a blood cortisol test, you may be asked to rest before the blood draw and avoid strenuous exercise beforehand. Fasting is not required for every cortisol test, so check your specific instructions rather than assuming you must avoid food.
If you are collecting saliva, you may need to avoid eating, drinking, brushing your teeth, or smoking for a specified period before the sample. Urine testing requires careful collection over the full 24-hour period, following the laboratory’s storage instructions.
Tell your doctor about all medicines and supplements you take, especially corticosteroids such as prednisone, hydrocortisone, or steroid-containing creams and inhalers. Some medicines can affect the result. Do not stop or change prescribed steroid medicines on your own, because suddenly stopping them can be dangerous.
MedlinePlus
+1
What Is the Best Time to Test Cortisol Levels?
The best time depends on the condition your doctor wants to investigate. Cortisol follows a daily pattern: levels generally rise around waking and fall toward the evening and night.
A blood cortisol test is often performed in the morning, sometimes around 8 a.m. Your doctor may request a second sample later in the day if comparing cortisol levels at different times is helpful.
A late-night saliva test is often used when checking for Cushing syndrome because cortisol should normally be low late at night. A 24-hour urine test measures cortisol excreted throughout the day rather than at one specific moment.
People who work night shifts, have unusual sleep schedules, or are acutely unwell may need specific instructions about when to collect their samples. Always follow the timing given by your healthcare provider.
MedlinePlus
+1
How to Read Cortisol Test Results
Cortisol test results show how much cortisol was measured in your sample. To understand the result, you need to consider the type of test, the collection time, the laboratory’s reference range, and your symptoms.
A blood result that falls within the laboratory’s expected range may be reassuring, but it does not always rule out a hormone disorder. Likewise, a result outside the reference range does not automatically mean you have a medical condition.
What Do High Cortisol Levels Mean?
High cortisol results can occur with Cushing syndrome, long-term use of certain steroid medicines, and some adrenal or pituitary conditions. Stress, illness, and other factors may also affect cortisol measurements.
If your doctor suspects Cushing syndrome, they may order a late-night salivary cortisol test, a 24-hour urinary free cortisol test, or a dexamethasone suppression test. More than one test is often needed to confirm the diagnosis.
What Do Low Cortisol Levels Mean?
Low cortisol results may point to adrenal insufficiency, including Addison disease, or a problem affecting ACTH production by the pituitary gland. Long-term steroid use can also suppress the body’s own cortisol production.
Your doctor may recommend an ACTH stimulation test to check whether the adrenal glands respond properly to a signal that normally prompts them to release cortisol. Results must be interpreted in context, because cortisol levels vary with time of day, medicines, and health status.
MedlinePlus
+1
What Causes High or Low Cortisol Levels?
Cortisol levels can change because of medical conditions, medicines, and the body’s response to illness or stress. Finding the cause is important because treatment depends on what is affecting hormone production.
Causes of High Cortisol
High cortisol levels over time may be caused by Cushing syndrome, certain adrenal or pituitary tumors, or tumors elsewhere that produce ACTH. Long-term treatment with corticosteroid medicines can also cause the body to experience the effects of excess cortisol.
Temporary changes can occur during physical illness or stressful situations. A high result alone does not confirm Cushing syndrome, so your doctor may recommend further testing.
Causes of Low Cortisol
Low cortisol may occur when the adrenal glands cannot make enough of the hormone. Addison disease is one possible cause. Problems with the pituitary gland can also reduce ACTH production, leaving the adrenal glands without enough stimulation.
Another possible cause is suppression of the body’s natural cortisol production after prolonged use of steroid medicines. This is why it is important to tell your doctor about steroid tablets, injections, inhalers, and creams before testing.
MedlinePlus
+1
Can You Test Cortisol Levels at Home?
Yes, some cortisol tests can be completed at home, depending on the test ordered by your healthcare provider. Saliva testing is one common option, especially when the doctor needs to measure cortisol late at night.
A home saliva kit usually includes a collection tube or swab and instructions explaining when and how to collect the sample. After collection, you return or send it to the laboratory according to the kit’s directions. Some tests may require samples collected on more than one night.
Home testing can make sample collection easier, but it cannot always tell you why your cortisol level is high or low. Commercial kits may also differ in quality and the type of test they offer. If you use a home test, discuss the result with a healthcare professional rather than relying on it to diagnose a condition yourself.
What Happens If Your Cortisol Test Is Abnormal?
An abnormal cortisol result does not always mean that you have a hormone disorder. Your doctor will review the result alongside your symptoms, medicines, medical history, and the time the sample was collected.
If high cortisol is suspected, further testing may include a late-night saliva test, a 24-hour urine test, or a dexamethasone suppression test. During the dexamethasone test, you take a prescribed dose of dexamethasone, and cortisol is measured afterward. In most people without Cushing syndrome, the medicine lowers cortisol production.
If low cortisol is suspected, your doctor may recommend an ACTH stimulation test. This test measures cortisol before and after a medicine that stimulates the adrenal glands. Depending on the results, you may be referred to an endocrinologist, a doctor who specializes in hormones.
Seek urgent medical care if you have severe weakness, repeated vomiting, severe abdominal pain, fainting, or confusion, especially if adrenal insufficiency is possible. These symptoms can signal a serious problem that should not wait for routine testing.
MedlinePlus
+1
Frequently Asked Questions
1. How can I test my cortisol levels?
You can test cortisol through a blood sample, a saliva sample, or a 24-hour urine collection. Your doctor will choose the method based on your symptoms and the condition being investigated.
2. What is the most accurate test for cortisol levels?
There is no single best test for every situation. Late-night salivary cortisol, 24-hour urinary free cortisol, and dexamethasone suppression testing are commonly used to investigate Cushing syndrome. Other tests may be more suitable when low cortisol is suspected.
3. Can I test cortisol levels at home?
Yes. Some laboratories provide home saliva collection kits. You must follow the collection instructions and have the results interpreted in the right medical context.
4. What time of day should cortisol be tested?
Blood cortisol is often measured in the morning. Late-night saliva testing is used for certain conditions because cortisol should normally fall at night. Follow your doctor’s instructions for the specific test.
5. Do I need to fast before a cortisol blood test?
Not always. Fasting depends on the test and any other blood tests ordered at the same time. Ask your laboratory or doctor before your appointment.
6. How do I know if my cortisol levels are high?
Possible signs include a rounder face, unexplained weight gain around the abdomen, easy bruising, wide purple stretch marks, and muscle weakness. Testing is needed to determine whether cortisol is responsible for these symptoms.
7. What are the symptoms of low cortisol?
Symptoms may include persistent fatigue, muscle weakness, weight loss, reduced appetite, abdominal pain, and low blood pressure. These symptoms can have other causes, so they need medical assessment.
8. How long does a cortisol test take?
A blood sample usually takes only a few minutes to collect. Saliva collection may take a few minutes, while a 24-hour urine test requires collecting samples over a full day. Laboratory processing time varies.
9. Can stress affect cortisol test results?
Yes. Physical or emotional stress can affect cortisol levels. Illness, exercise, sleep patterns, and certain medicines may also influence results.
10. Can a blood test alone diagnose high cortisol?
Usually not. A blood cortisol result alone is generally insufficient to diagnose Cushing syndrome. Your doctor may need other tests and a review of your medical history before reaching a diagnosis.
MedlinePlus
+1
Conclusion
Testing cortisol levels can help doctors investigate hormone problems affecting the adrenal and pituitary glands. Blood, saliva, and urine tests each serve different purposes, and the right choice depends on your symptoms and medical history.
