Cortisol is a hormone made by the adrenal glands. It helps the body manage stress, regulate blood pressure, and metabolise fats and sugars. High or low cortisol levels in either your blood or urine may indicate some health problems. The normal ranges are the same for both men and women.
Cortisol Blood Tests
For a cortisol blood test, you may need to provide two blood samples―one in the morning, and one in the afternoon. According to WebMD.com, the normal range for morning blood cortisol levels in an adult human is 5 to 23 micrograms per decilitre (mcg/dl) or 138 to 635 nanomoles per litre (nmol/L). In the afternoon, the normal range is 3 to 13mcg/dl or 83 to 359 nmol/L.
Cortisol Urine Tests
For a cortisol urine test, you must collect all of your urine during an exactly 24-hour period. According to WebMD.com, the normal range for cortisol levels in a 24-hour urine sample of an adult human is less than 100 micrograms (mcg) or less than 276 nanomoles (nmol).
Factors Affecting Test Results
For more accurate results, avoid strenuous activity, emotional stress, taking birth control pills or amphetamines, or eating directly before your test.
Cortisol Levels Vary from Morning to Night
Cortisol levels rise and fall throughout the day. In a normal cycle, levels are highest in the early morning and lowest right after falling asleep.
Implications of High or Low Cortisol Levels
Abnormally high cortisol levels may indicate Cushing's Syndrome, when overactive adrenal glands produce too much cortisol, resulting in weight gain, fatigue, diabetes or depression. Abnormally low cortisol levels may indicate damage to the adrenal or pituitary glands.