Does this test have other names?
Blood cortisol; plasma cortisol; cortisol, plasma
What is this test?
A serum cortisol test may help in the diagnosis of two fairly uncommon medical conditions:
Cushing syndrome and Addison disease. The test also screens for other diseases that
affect your pituitary and adrenal glands. It does so by measuring your blood level
of a stress hormone called cortisol.
Cortisol is a steroid hormone made by your adrenal glands. It helps your body respond
to stress, regulate blood sugar, and fight infections. In most people, cortisol levels
are highest in the morning when they wake up and lowest around midnight. Your body
also pumps out excess cortisol when you're anxious or under intense stress, which
can affect your health if the levels stay too high for too long. If your cortisol
levels are too high or too low, you may have a condition that needs treatment.
Why do I need this test?
You may need this test if your healthcare provider suspects a medical problem caused
by too much or too little cortisol.
A high cortisol level could be a sign of Cushing syndrome. Symptoms of Cushing syndrome
Obesity, especially in the torso, face, and neck, with thinner arms and legs
High blood pressure
High blood sugar
Thin skin that bruises easily
Pink or purple streaks on the stomach, thighs, or buttocks
For women, irregular menstrual periods and excess hair on the face and chest
Too little cortisol could be a sign of Addison disease, also called primary adrenal
insufficiency. It could also be a sign of another problem with your adrenal glands.
This may cause these symptoms:
Muscle and joint pain
Fatigue, or extreme tiredness
Low blood pressure
Nausea and/or vomiting
Dark patches of skin
For women, decreased armpit and pubic hair and decreased sexual desire
You may also need this test if your healthcare provider suspects an adrenal crisis.
This can be a life-threatening emergency. Symptoms include:
Shock, or very low blood pressure and loss of consciousness
Sudden, severe belly pain
Vomiting and diarrhea
Weakness and tiredness
What other tests might I have along with this test?
Besides a blood test for cortisol, your healthcare provider may test the cortisol
levels in your urine or saliva.
Your healthcare provider will likely order other blood tests that measure your body's
response to certain hormones to help determine the cause of your abnormal cortisol
You may also have tests to look inside your body for abnormal growths or tumors. These
can affect cortisol levels. Tests may include:
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used
for the test, and other things. Your test results may not mean you have a problem.
Ask your healthcare provider what your test results mean for you.
Your test result will tell you the level of cortisol in your blood at the time of
the test. Normal cortisol levels are usually highest early in the morning and lowest
about midnight. Normal ranges vary depending on the type of test. For most tests,
normal ranges are:
Abnormal cortisol levels are often caused by long-term use of steroids (glucocorticoid
medicines), such as those taken to control asthma, autoimmune diseases, or inflammation.
If this is the cause, your healthcare provider may gradually reduce your doses of
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
The timing of the test is important, because cortisol levels change throughout the
day. It's common to test serum cortisol twice in the same day – early in the morning
and again around 4 p.m.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
Your cortisol levels change in response to many events. For instance, if you work
nights and sleep during the day, your cortisol levels may not be in the normal range.
Your cortisol levels may be higher than normal because of physical trauma and stress.
Women in their last three months of pregnancy and highly trained athletes may have
higher-than-normal levels of cortisol. Other reasons your cortisol level may be higher
than normal include depression, alcoholism, malnutrition, and panic disorder.
A number of medicines, especially oral contraceptives and any medicine that contains
glucocorticoids, or steroid hormones similar to cortisol, can also affect your cortisol
How do I get ready for this test?
You may need to rest before the test to keep stress levels down. You will also need
to avoid medicines that can affect the results of the test. Be sure your healthcare
provider knows about all medicines, herbs, vitamins, and supplements you are taking.
This includes medicines that don't need a prescription and any illicit drugs you may