Cortisol Levels: Saliva Test Vs. Blood Test

Cortisol is a hormone produced by the adrenal glands (above the kidneys). From breaking down protein, glucose and lipids to maintaining blood pressure and regulating the immune system, it is crucial to good health to maintain a normal cortisol level.

Significance

• Labs can test cortisol levels in blood, saliva and urine samples to evaluate cortisol production. Doctors use cortisol testing to diagnose Cushing's syndrome (abnormally high cortisol levels) and Addison's disease (abnormally low cortisol production).

Time Frame

• Cortisol production in our bodies follows what is known as a diurnal variation or circadian rhythm. The hormone production rises in the morning, peaking around 8 a.m., and declines in the evening, with the lowest cortisol level measured at midnight.

Sample Collection

• Laboratory personnel draw blood from a vein in the arm for blood cortisol testing. For saliva testing, the patient chews on a cotton tube for two to three minutes, then places it in a plastic tube for transport to the lab.

Advantages

• Saliva testing is noninvasive, more convenient and reduces stress that may be associated with a blood draw. Stress can cause a temporary increase in cortisol levels.

Considerations

• In both blood and saliva testing, factors such as pregnancy, emotional stress, certain drugs, obesity and illness can increase cortisol levels. Hypothyroidism and steroid hormones can decrease cortisol levels.

Expert Insight

• Doctors are using salivary cortisol testing more frequently to help diagnose Cushing's syndrome because of the ease of collecting samples at different times of day and comparing the results.