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Overview

Cortisol Blood Test: Overview

A cortisol blood test measures the amount of cortisol in a blood sample. Cortisol is a hormone made by the adrenal glands that helps regulate metabolism, blood pressure, immune activity, and the body’s response to stress. Testing can help clinicians assess how the adrenal glands and pituitary gland are working.

When It Is Needed

When Is a Cortisol Blood Test Needed?

Clinicians may order a cortisol blood test when symptoms, examination findings, or other test results suggest that the body is making too much or too little cortisol. The test may be part of an evaluation for conditions such as Cushing syndrome, adrenal insufficiency, or a pituitary-related problem. It is generally ordered because of a specific clinical concern rather than as routine screening for everyone.

  • Unexplained weight gain or weight loss
  • Muscle weakness
  • Easy bruising or unusual skin changes
  • High blood pressure
  • Persistent fatigue
  • Dizziness or low blood pressure
  • Abnormal sodium or potassium results

Everyday stress, disrupted sleep, an illness, or symptoms alone do not prove that cortisol is high or low. Medicines and other health conditions can also affect cortisol levels, so a clinician decides whether testing is appropriate and how the findings should be evaluated.

Preparation

How to Prepare for a Cortisol Blood Test

  • Confirm whether you need to fast before the appointment.
  • Follow the requested appointment time for sample collection.
  • Avoid unusual strenuous activity if your clinician instructs you to do so.
  • Bring a complete list of your medicines and supplements.

Your clinician or laboratory may request a morning sample or another specific collection time because cortisol follows a daily pattern. Instructions can vary based on the reason for testing and whether other blood or laboratory tests are being collected at the same time.

During the Test

During the Cortisol Blood Test

A cortisol blood test is usually a single-session venous blood draw. A healthcare professional cleans the skin, places a needle into a vein, fills one or more collection tubes, and removes the needle.

  • A brief needle prick or stinging sensation
  • Pressure from the tourniquet or needle
  • Mild bruising or soreness afterward
  • Lightheadedness in some people
  • A collection that generally takes only a few minutes

The sample is sent to a laboratory to measure cortisol levels. You can usually resume normal activities after the draw unless your clinician gives you different instructions.

Risks

Risks of a Cortisol Blood Test

  • Brief pain or stinging at the puncture site
  • Bruising
  • Minor bleeding
  • Temporary soreness
  • Infection at the puncture site
  • Lightheadedness or fainting

Serious complications from a routine blood draw are uncommon. Tell the person collecting the sample if you have fainted during blood draws before or have a bleeding disorder.

Results

Cortisol Blood Test Results

The report usually gives a numeric cortisol value, its units, and a reference range supplied by the laboratory. The expected range may differ according to the collection time, testing method, age, pregnancy status, and other factors. Compare the result with the range and collection details shown on your own report.

What high or low results may mean

High or low cortisol can have several explanations, including medicines, acute illness, sleep or stress effects, and conditions affecting the adrenal or pituitary glands. One result is not usually enough to diagnose a disorder. Depending on the findings, a clinician may repeat the cortisol test or order urine, saliva, stimulation, or suppression tests.

Diseases & Conditions

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