Can this result diagnose a condition on its own?

No. Hormone tests are interpreted together with symptoms, medical history, and other laboratory results.

Which reference range should I use?

Use the reference interval provided by the laboratory that performed your test.

When should I discuss the result with a healthcare professional?

Results that are clearly outside range, persistent, or inconsistent with symptoms should be reviewed by a healthcare professional.

Information about a laboratory test

Cortisol: What Does This Blood Test Measure?

Measures cortisol made by the adrenal glands; cortisol can be tested in blood, urine, or saliva, while this definition uses serum/plasma as the default specimen.

Test summary

Test name: Cortisol
Abbreviations: Cortisol
Category: Endocrinology / Adrenal
Panel: Adrenal Function Tests
Specimen: Serum / plasma
Common units: µg/dL, nmol/L

What does the test measure?

Measures cortisol made by the adrenal glands; cortisol can be tested in blood, urine, or saliva, while this definition uses serum/plasma as the default specimen.

Why is the test ordered?

Helps evaluate Cushing syndrome, adrenal insufficiency, and disorders involving the pituitary-adrenal axis.

Information about a low result

Low cortisol may occur with adrenal insufficiency or inadequate ACTH signaling; one basal result often cannot establish the cause.

Information about a high result

High cortisol may occur with prolonged glucocorticoid exposure or excessive cortisol production; additional testing is required for diagnosis.

Reference and clinical context

Use the reference interval printed on your own laboratory report first. Hormone results may vary with the assay, age, sex, pregnancy, menstrual-cycle phase, and sampling time.

Reference range 1

>= 5 – <= 25 µg/dL

Population: Adults
Specimen: Serum / plasma

Example reference interval

Example for a blood sample collected around 08:00; cortisol is strongly time-dependent.

Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.

Interpretation notes

Cortisol has a strong daily rhythm. Sampling time should be stored with the result; morning and afternoon values should not be compared to the same interval.

Related specialties

Endocrinology
Internal Medicine
Pediatric Endocrinology

Frequently asked questions

More information about this test

Sources

Cortisol Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2024 · Cortisol testing; circadian timing; adrenal/pituitary context · Verified: Aug 11, 2026
Cortisol blood test — U.S. National Library of Medicine (MedlinePlus)
Government medical encyclopedia · 2025 · Example 8 a.m. cortisol interval and time-of-day caveat · Verified: Aug 11, 2026
Adrenocorticotropic Hormone (ACTH) — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2023 · ACTH use with cortisol and pituitary/adrenal interpretation · Verified: Aug 11, 2026