Platform
Company
Endocrine & Reproductive
Review status
Currently under review
Pending specialist review and validation.
Cortisol is a steroid hormone made by your adrenal glands that helps your body respond to stress, maintain blood pressure and blood sugar, and regulate energy and the sleep‑wake cycle. A cortisol test measures the amount of this hormone in your blood at a specific time, usually in the morning and sometimes later in the day, because levels naturally rise and fall across the day.
Your clinician may order cortisol alone or as part of dynamic testing that checks how your adrenal and pituitary glands respond to stimulation or suppression. Blood cortisol reflects total cortisol, which includes hormone bound to proteins and the free portion that is biologically active.
Cortisol testing helps evaluate symptoms such as fatigue, weakness, dizziness, unintentional weight change, high or low blood pressure, and changes in skin, mood, or blood sugar. It is a key tool for assessing adrenal insufficiency and conditions of cortisol excess, and for monitoring recovery or suppression of the adrenal glands during or after steroid treatment.
Your clinician may use this test when physical findings or other lab results suggest an adrenal or pituitary problem, during evaluation of unexplained illness, or to guide safe use of glucocorticoid medicines. Results are interpreted alongside your symptoms, timing of collection, and other hormone tests.
Cortisol varies with the time of day, sleep, and stress, so your result is interpreted in the context of when the sample was collected and your current health. A single result rarely gives a complete picture. If your level is higher or lower than expected, your clinician may repeat the test at a different time, review medications and recent stressors, or order follow‑up tests such as an ACTH stimulation test, a dexamethasone suppression test, a late‑night salivary cortisol, or a urine free cortisol.
Pregnancy, estrogen therapy, liver disease, and changes in cortisol‑binding proteins can shift total cortisol without reflecting the biologically active portion. In such cases, tests that estimate free cortisol or dynamic testing may be more informative. If you use steroid medicines, do not stop them on your own; your clinician will advise if any dose adjustments or temporary holds are appropriate for accurate testing and for your safety.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Cortisol follows a daily rhythm, typically higher in the morning and lower at night. Shift work, jet lag, or disrupted sleep can shift this pattern and change what is considered expected for you.
Pain, fever, surgery, trauma, or emotional stress can raise cortisol temporarily. Hospitalization or severe illness can alter results, so timing and clinical context matter.
Prednisone, hydrocortisone, dexamethasone, inhaled or topical steroids, and adrenal extracts can change measured cortisol or suppress adrenal function. Drugs like ketoconazole, rifampin, certain anti‑seizure drugs, mifepristone, and opioids can also affect levels.
Pregnancy and estrogen therapy, including some contraceptives, raise cortisol‑binding globulin, which increases total cortisol while free cortisol may be unchanged. Your clinician may choose tests that assess free hormone when needed.
Different laboratory methods can yield slightly different results. High‑dose biotin supplements may interfere with some immunoassays; tell your clinician about supplements so they can advise on holding them before testing.
Conditions that alter protein production or hormone clearance can change total cortisol and its interpretation. Your clinician will consider your overall health and may use additional tests.
Following exact collection instructions, including target collection times and any medication guidance, improves the usefulness of results and reduces the need for repeat testing.
References