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's syndrome and Addison's 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's syndrome. Symptoms of Cushing's
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's 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
Belly (abdominal) pain
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 doctor 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 abdominal (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 doctor will likely order other blood tests that measure your body's response
to certain hormones to help determine the cause of your abnormal cortisol levels.
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?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
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 doctor may gradually reduce your doses of these medicines.
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
arm. 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?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly 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 a 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 doctor 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 use.