Cortisol: Normal Range, What High & Low Levels Mean

A cortisol blood test measures the level of cortisol — your body's main glucocorticoid hormone — circulating in your bloodstream at the moment the sample was taken. Cortisol is made by your adrenal glands and acts as a kind of master regulator: it manages how your body converts food into energy, influences your blood pressure, helps control inflammation, and plays a role in your sleep-wake cycle. Because cortisol rises and falls throughout the day in a predictable pattern, knowing when your sample was collected is just as important as the number itself. Discuss what your specific result means in the context of your health history with your healthcare provider.

Cortisol peaks shortly after you wake up, which is why the standard blood draw is scheduled between 7 and 9 AM. According to Mayo Clinic Laboratories, a normal morning cortisol level for adults falls between 6 and 23 mcg/dL (micrograms per deciliter). Later in the day — between 3 and 5 PM — the normal range drops to 3–16 mcg/dL, reflecting the hormone's natural daily decline. Labs can use slightly different methods, so the reference range printed on your report may look a little different from these figures. Always compare your result to the range provided by the lab that processed your sample, and talk with your healthcare provider about what your number means for you.

Several things can push cortisol above the normal range. Physical or psychological stress, depression, anxiety, obesity, poorly controlled diabetes, pregnancy (especially in the third trimester), and certain medications like oral contraceptives can all raise your reading. On the more serious end, Cushing's syndrome — a condition where your body is exposed to excess cortisol over a long period — can result from a tumour on the pituitary or adrenal glands, or from prolonged use of corticosteroid medications. A single elevated result does not confirm Cushing's syndrome; your doctor will consider your full clinical picture before pursuing further investigation. Please discuss any elevated cortisol result with your healthcare provider rather than drawing conclusions on your own.

A cortisol reading below the reference range suggests your adrenal glands may not be producing enough of the hormone. Possible causes include Addison's disease (also called primary adrenal insufficiency), a condition where the adrenal glands themselves are damaged; secondary adrenal insufficiency, where the pituitary gland fails to send the signal that prompts cortisol production; abrupt stopping of long-term corticosteroid medication; hypothyroidism; and hypopituitarism. Low cortisol does not automatically mean you have Addison's disease — timing, stress levels, and other factors influence the result. Your healthcare provider can order additional tests to identify the underlying cause and guide next steps for your specific situation.

High cortisol over time can cause weight gain concentrated in the abdomen and face, purple or pink stretch marks, thin skin that bruises easily, muscle weakness (particularly in the thighs and upper arms), high blood pressure, elevated blood sugar, mood changes such as depression or anxiety, and irregular periods in women. Persistently low cortisol tends to produce a different set of signs: fatigue, unexplained weight loss, nausea, low blood pressure that makes you feel dizzy when you stand, intense salt cravings, skin darkening, and depression. In severe cases, very low cortisol can trigger an adrenal crisis — a medical emergency involving severe vomiting, a dangerous drop in blood pressure, and potential loss of consciousness. If any of these symptoms sound familiar, talk with your healthcare provider promptly.

An out-of-range cortisol result is a starting point, not a final answer. Many everyday factors — the exact time your blood was drawn, recent physical activity, stress, poor sleep, or certain medications — can shift your cortisol level above or below the standard range without indicating a serious condition. Your doctor may ask you to repeat the test at a specific time of day, collect a 24-hour urine cortisol sample, or undergo a stimulation or suppression test to get a more complete picture of how your adrenal glands are working. The best next step is to bring your full lab report to your healthcare provider so they can interpret your result alongside your symptoms, medications, and medical history.