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At a Glance
Why Get Tested?
When To Get Tested?
When your doctor suspects excess or deficient cortisol production
Sample Required?
A blood sample drawn from a vein in the arm or a urine sample; sometimes a saliva sample may be used
What is being tested?
Cortisol is a hormone produced by the adrenal glands. Production and secretion of cortisol is stimulated by ACTH (adrenocorticotropic hormone), a hormone produced by the pituitary gland – a tiny organ located inside the head below the brain. Cortisol has a range of roles in the body. It helps break down protein, glucose, and lipids, maintain blood pressure, and regulate the immune system. Heat, cold, infection, trauma, stress, exercise, obesity, and debilitating disease can influence cortisol concentrations. The hormone is secreted in a daily pattern, rising in the early morning, peaking around 8 am, and declining in the evening. This pattern, which is sometimes called the “diurnal variation” or “circadian rhythm,” changes if you work irregular shifts (such as the night shift) and sleep at different times of the day.

Inadequate amounts of cortisol can cause nonspecific symptoms such as weight loss, muscle weakness, fatigue, low blood pressure, and abdominal pain. Sometimes decreased production combined with a stressor can cause an adrenal crisis that requires immediate medical attention.

Too much cortisol can cause increased blood pressure, high blood sugar, obesity, fragile skin, purple streaks on the abdomen, muscle weakness, and osteoporosis. Women may have irregular menstrual periods and increased facial hair; children may have delayed development and a short stature.

How is the sample collected for testing?

Typically, blood will be drawn from a vein in the arm, but sometimes urine or saliva may be tested. Cortisol blood tests may be drawn at about 8 am, when cortisol should be at its peak, and again at about 4 pm, when the level should have dropped. Sometimes a resting sample will be obtained late in the evening to measure cortisol when it should be at its lowest concentration in the blood (about midnight). Obtaining more than one sample allows the doctor to evaluate the daily pattern of cortisol secretion (the diurnal variation). This pattern may be disrupted with excess cortisol production – the maximum amount may be at or near normal concentrations, but levels may not fall as they should throughout the day. A single morning sample may be sufficient to detect decreased concentrations of cortisol.

Sometimes urine is tested for cortisol; this usually requires collecting all the urine produced during a day and night (a 24-hour urine), but sometimes may be done on a single sample of urine collected in the morning. A 24-hour urine sample may be ordered to measure the amount of free (not protein bound) cortisol. This sample will show the total amount of unbound cortisol secreted in the urine but it will not allow doctors to evaluate variations in cortisol secretion.

Cortisol testing of saliva can be performed. Although the sampling is less stressful than a blood draw, it requires special care in obtaining the sample. Often, the sample is collected between 11 pm and midnight, the time when cortisol is normally at its lowest, to help diagnose Cushing’s syndrome.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.
Accordion Title
Common Questions
  • How is it used?
    Blood and urine tests for cortisol are used to help diagnose Cushing's syndrome and Addison's disease, two serious adrenal disorders. Some physicians are using salivary cortisol to diagnose Cushing's syndrome as well as to evaluate possible stress-related disorders, although these uses are not widespread.

    Both the urine and saliva tests are most frequently used to evaluate excess cortisol production.

    Once an abnormal cortisol concentration has been detected, the doctor will do additional testing to help confirm the excess or deficiency and to help determine its cause.

    Dexamethasone Suppression
    If there is excess cortisol production, the doctor may perform a dexamethasone suppression test to help determine whether the cause of the cortisol is related to excess ACTH production by the pituitary. This test involves giving the patient oral dexamethasone (a synthetic glucocorticoid) and then measuring their blood and urine cortisol levels. Dexamethasone suppresses ACTH production and should decrease cortisol production if the source of the excess is pituitary related. There are a variety of dosing schedules, but the medication is usually given every 6 hours for either 2 or 4 days prior to blood or urine collection. Separate 24-hour urine samples are collected prior to and throughout the testing period and then the blood and urine samples are measured for cortisol and evaluated.

    ACTH Stimulation
    If the findings of the initial blood and/or urine tests indicate insufficient cortisol production, the doctor may order an ACTH stimulation test. This test involves measuring the concentration of cortisol in a patient’s blood before and after an injection of synthetic ACTH. If the adrenal glands are functioning normally, then cortisol levels will rise with the ACTH stimulation. If they are damaged, then the response will be limited. A longer version of this test (1-3 days) may be performed to help distinguish between adrenal and pituitary insufficiency.

  • When is it ordered?
    A cortisol test may be ordered when a patient has symptoms that suggest Cushing’s syndrome (obesity, muscle wasting, and muscle weakness) or Addison’s disease (weakness, fatigue, increased pigmentation, among others).

    Suppression or stimulation testing is ordered when initial findings are abnormal. Cortisol testing may be ordered at intervals when patients are being or have been treated for Cushing’s syndrome or Addison’s disease to monitor the effectiveness of treatment.

  • What does the test result mean?
    In normal people, cortisol levels are very low at bedtime and at their highest just after waking. This pattern will change if a person works irregular shifts (such as the night shift) and sleeps at different times of the day. With Cushing’s syndrome, this pattern is typically lost.

    Increased or normal cortisol concentrations in the morning along with levels that do not drop in the afternoon and evening suggest an overproduction of cortisol. If this excess cortisol is suppressed during a dexamethasone suppression test, it suggests that the excess cortisol is due to increased pituitary ACTH production. If it is not suppressed, then the increased cortisol could be due to an ACTH-producing tumor outside of the pituitary, due to a problem with the adrenal gland, or due to a medication that the patient is taking.

    If the adrenal glands are overactive, then a patient may have Cushing’s syndrome, with symptoms and signs caused by prolonged exposure to the effects of too much cortisol. This may be due to excess production of cortisol by the adrenal glands (which is frequently due to a benign adrenal tumor) or excess ACTH stimulation (due to a pituitary or other ACTH-producing tumor). It can also be seen in patients who must take corticosteroid medications, such as those used to treat asthma. If insufficient cortisol is present and the patient responds to an ACTH stimulation test, then the problem is likely due to insufficient ACTH production by the pituitary. If cortisol levels do not respond to the ACTH stimulation test, then it is more likely that the problem is based in the adrenal glands. If the adrenal glands are underactive, due to adrenal damage or insufficient ACTH production, then the patient is said to have adrenal insufficiency. If decreased cortisol production is due to adrenal damage, then the patient is said to have Addison’s disease.

    Once an abnormality has been identified and associated with the pituitary gland, adrenal glands, or other cause, then the doctor may use other testing such as CT (computerized tomography) or MRI (magnetic resonance imaging) scans to locate the source of the excess (such as a pituitary, adrenal, or other tumor) and to evaluate the extent of any damage to the glands.

  • Is there anything else I should know?
    Pregnancy, physical and emotional stress, and illness can increase cortisol levels. Cortisol levels may also increase as a result of hyperthyroidism or obesity. A number of drugs can also increase levels, particularly oral contraceptives (birth control pills), hydrocortisone (the synthetic form of cortisol), and spironolactone. Adults have slightly higher cortisol levels than children do.

    Hypothyroidism may decrease cortisol levels. Drugs that may decrease levels include some steroid hormones.

    Salivary cortisol testing is being used more frequently to help diagnose Cushing's syndrome and stress-related disorders but still requires specialized expertise to perform.

  • Do I need both tests (blood and urine) or is one better than the other?
    If your doctor suspects Cushing's syndrome, usually both blood and urine are tested. Blood cortisol is easier to collect but is affected more by stress than is the urine test. Salivary cortisol may sometimes be tested instead of blood cortisol.
  • How do I tell if a high cortisol level isn’t just from stress? 
    There are several approaches that your doctor can take. The simplest involves repeating tests at a time when you feel less stressed. Your doctor can also give you varying doses of a medicine that replaces cortisol (usually dexamethasone) to see if this decreases your cortisol level. Multiple tests are often needed to tell if stress or disease is causing a high cortisol level.
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