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What do cortisol levels mean and how to exam them

The cortisol examination is usually asked to check for problems with the adrenal glands or the pituitary gland, because cortisol is a hormone produced and regulated by these glands. Therefore, when there is a change in the normal values of cortisol, there is a change in one of the glands. Using this examination it is possible to diagnose diseases such as Cushing's Syndrome in cases of high cortisol or Addison's Disease in cases of low cortisol for example.

Cortisol is a hormone that helps control stress, decrease inflammation, improve the immune system, and aid in the metabolism of proteins, fats and carbohydrates, keeping blood sugar levels constant. See what the hormone cortisol does in the body.

There are 3 different types of cortisol screenings, which include:

  • Salivary Cortisol Exam: Evaluates the amount of cortisol in saliva, helping to diagnose chronic stress or diabetes;
  • Urinary cortisol examination: measures the amount of free cortisol in the urine, and the urine sample should be collected for 24 hours;
  • Blood Cortisol Exam: Evaluates the amount of protein cortisol and free cortisol in the blood, helping to diagnose Cushing's Syndrome, for example. 

The concentration of cortisol in the body varies during the day, so normally two collections are performed: one between 7 and 10h, called the basal cortisol examination or 8 hour cortisol examination, and another at 4pm called the cortisol examination 16 hours, and is usually performed when there is suspicion of this hormone being in excess in the body.

What do cortisol levels mean and how to exam them

How to Prepare for the cortisol exam

Preparation for the cortisol examination is especially important in cases where it is necessary to draw a blood sample. In these cases, it is recommended:

  • Fasting 4 hours prior to collection, either at 8 or 16 hours;
  • Avoid exercising the day before the exam;
  • Stand for 30 minutes prior to examination.

In addition, in any type of cortisol examination, the doctor should be informed about the medication you are taking, especially in the case of corticosteroids such as dexamethasone, as they can cause changes in the results.

In the case of salivary cortisol examination, the collection of saliva should preferably be done up to 2 hours after waking up. However, if done after a main meal you should wait 3 hours and avoid brushing your teeth during this time.

Reference values

The reference values of cortisol vary according to the samples collected and the laboratory in which the examination was carried out, and may be:

MaterialReference values

Men: less than 60 µg/day

Women: less than 45 µg/day


Between 6h and 10h: less than 0,75 µg/mL

Between 16h and 20h: less than 0,24 µg/mL


Morning: 8,7 a 22 µg/dL

Afternoon: less than 10 µg/dL

Changes in blood cortisol values may indicate health problems such as pituitary tumor, Addison's disease, or Cushing's syndrome, for example, where cortisol is elevated.

Changes in cortisol results

Cortisol test results may be altered due to heat, cold, infections, excessive exercise, obesity, pregnancy or stress and may not be indicative of disease. Therefore, when there is an alteration in the results, it may be necessary to repeat the examination to see if there has been interference of any factor.

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