What Is a Cortisol Test?

What to Expect When Undergoing This Test

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Cortisol is a hormone that is made in the adrenal glands, which are located next to the kidneys. Cortisol is used by the body for several reasons, including fighting infections, mounting a stress response, and regulating blood glucose levels, blood pressure, and metabolism.

Sometimes called the “stress hormone,” the level of cortisol in the body can be affected by a number of diseases or conditions, or even by some types of medications. A cortisol level that is too high or too low can have a serious effect on health.

A cortisol test is a type of blood test that measures the level of cortisol in the body. Other tests that could be used to measure cortisol include a urine test or a saliva test.

Purpose of Test

Disorders of the adrenal gland can cause the adrenal glands to make too much or too little cortisol. A cortisol level test can help physicians to learn the cortisol level in the body.

Levels that are found to be outside the spectrum of what is normal could indicate that there is a problem with the adrenal glands. Cushing’s syndrome is a rare condition that causes the body to make too much cortisol. Addison’s disease, when the body makes too little cortisol, is another rare condition.

Most cases of Cushing’s syndrome are caused by a benign tumor growing on the pituitary gland, which is called Cushing’s disease. In a minority of cases, Cushing’s disease is caused by a cancerous tumor which is growing outside of the pituitary gland or by an abnormality in the adrenal gland (such as a tumor). Most cases of Cushing’s syndrome occur in people between the ages of 20 and 50 years, and it affects women more often than it does men.

Symptoms of Cushing's syndrome may include:

  • Bruising easily
  • High blood pressure
  • Hyperglycemia (high blood sugar)
  • Irregular periods and hair growth on the face
  • Muscle weakness
  • Obesity, especially in the abdomen
  • Striae (stretch marks)

Addison’s disease is a condition that can be life-threatening, but it is uncommon. When the adrenal glands stop making enough cortisol or other hormones, it can result in primary or secondary adrenal insufficiency. Primary adrenal insufficiency is tied to a lack of cortisol being created by the adrenal glands.

This may be caused by damage to the adrenal gland such as from an autoimmune condition, a tumor, or an infection.

Symptoms of Addison’s disease may include:

  • Abdominal pain
  • Decreased appetite
  • Depression
  • Diarrhea
  • Extreme fatigue
  • Fainting
  • Hypoglycemia (low blood sugar)
  • Hypotension (low blood pressure)
  • Hyperpigmentation (a darkening of the skin)
  • Irritability
  • Loss of body hair
  • Muscle or joint pains
  • Nausea
  • Salt cravings
  • Sexual dysfunction
  • Vomiting
  • Weight loss

The causes of a cortisol insufficiency or surplus are uncommon.

However, when a problem with the cortisol level is suspected based on symptoms or other diseases or conditions, a cortisol level test may be ordered. 

Risks and Contraindications

The cortisol test is a blood test, which is considered a very safe procedure, so there are few associated risks. Risks would be the same for any other type of blood test. Some people may experience pain when blood is taken but this is usually minor and stops when the test is over. Bruising may also occur in the area where the blood was taken from a vein (usually on the arm).

Other risks of blood tests are rare but can include excessive bleeding, fainting or dizziness, hematoma (a collection of blood under the skin), and/or infection.

Before the Test

A physician will discuss the timing and the location of the test, which may be done in two parts. It may be recommended to rest prior to the blood draw because cortisol levels can be increased with stress. As with any blood draw, it’s important to be well hydrated by drinking enough water before the test in order to make the veins easier to access.

Timing

A cortisol blood test should not take long, usually only a few minutes. However, because cortisol levels change throughout the day, two different blood draws may be needed. The first blood test should be done in the morning when cortisol levels are higher. Another blood draw should be done again in the late afternoon when cortisol levels are lower.

Location

Blood tests may be done at a hospital, a physician’s office, or a laboratory. Where the test is done with be based on the availability of facilities as well as patient preference and insurance coverage.

What to Wear

No special clothing is usually needed for a blood test, but wearing a short-sleeved shirt makes it easier to access the arms.

Food and Drink

Check with a doctor about any restrictions on medications and food or drink, but in most instances, there are no specific recommendations.

It may help to be well hydrated, so drinking enough water prior to the test and avoiding caffeine may help.

Cost and Health Insurance

Check with an insurance carrier about coverage for a blood test by calling the number on the back of the insurance card.

During the Test

A blood test is typically relatively quick and simple. Patients may be asked to verify their information several times, usually when checking in, before the draw, and sometimes after the draw.

Patients are shown into either a private room or a semi-private area where the blood draw will take place. After sitting comfortably, the phlebotomist will place a tourniquet on the upper part of the non-dominant arm and look for the best vein to use.

A small needle will be inserted into the arm to draw the blood, which is then captured in one or more vials. A cotton ball and a bandage will be placed over the area after the test.

After the Test

Applying some pressure to the draw location immediately after the test can help prevent some of the bruising that may occur. If bruising does happen, it usually only lasts a few days. While not absolutely necessary, it may be more comfortable to avoid strenuous activity with the arm used for the draw for the rest of the day. 

If there is a hematoma, it may help to apply an ice pack wrapped in a towel to the area a few times, in 20-minute sessions during the first 24 hours. After the first 24 hours, applying a moist heat for about 20 minutes a few times over the next 24 hours may also help.

Check with a doctor about taking ibuprofen or other non-steroidal anti-inflammatory medications because these drugs may increase bleeding.

Interpreting Results

After a few days, the lab will have processed the blood sample and a physician will provide the results. Labs have different ways of classifying the normal range for cortisol, so it will be necessary to judge the results in the context of how that particular lab measures cortisol.

One reference range for a normal cortisol level from a blood sample drawn at 8 in the morning is between 7 and 28 micrograms of lead per deciliter of blood (μg/dL). For blood drawn in the afternoon, the reference range might be between 2 and 18 μg/dL. (To convert a cortisol level from μg/dL to nmol/L, multiply by 27.59.)

Follow-Up

In the event that the cortisol levels are found to be too high or too low, there may be a need for follow-up and for treatment. For cortisol levels that are too low (which could mean Addison’s disease), it's likely that more testing will be needed. One possible treatment is that medication such as hydrocortisone, prednisone, or methylprednisolone may be prescribed to replace cortisol in the body.

Dietary changes may also be needed to add more salt, especially during hot weather or during heavy exercise.

During times of stress, such as from a medical condition like an infection, an increase in the dose of medication may be prescribed by a doctor. Other therapies may also be necessary.

In the event of high cortisone levels (which could mean the presence of Cushing’s syndrome), further testing may be needed to determine the cause. If there is a tumor causing the higher cortisone levels, treatment might be needed to remove or to reduce the size of the tumor. Dietary changes may also be recommended, such as reducing sodium and fat in the diet. In most cases, Cushing’s syndrome can be cured.

A Word From Verywell

The cortisol level test is a fairly simple blood draw. However, when a cortisone level imbalance is found, there may be a need for further testing and treatment will be prescribed. Keeping in close contact with a doctor about the cortisol level test and the subsequent decisions that need to be made is important.

A diagnosis of Cushing’s syndrome or Addison’s disease can bring a significant amount of change and stress. Know that it's important to keep in touch with healthcare providers and seek help from specialists such as a dietician and a mental health professional in order to manage the condition properly. In most cases, these conditions are very manageable.

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Article Sources

  • Griffing GT. Serum Cortisol. Medscape.

  • The National Institute of Diabetes and Digestive and Kidney Diseases. Addison’s Disease. National Institutes of Health.

  • The National Institute of Diabetes and Digestive and Kidney Diseases. Cushing’s Syndrome. National Institutes of Health.