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Cortisol, Serum or Plasma, Substance Concentration

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of cortisol, a hormone produced by your adrenal glands, in your blood. Cortisol helps regulate metabolism, immune response, and stress reactions.

Quick summary

["Cortisol helps your body respond to stress and maintain balance, but abnormal levels may signal health concerns."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
58675-0
Short code
Cortis 8 AM Sal-sCnc
Synonyms
Cortis 8 AM Sal-sCnc
Category
hormone
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order cortisol testing to diagnose or monitor conditions like Cushing’s syndrome (too much cortisol), Addison’s disease (too little cortisol), or adrenal gland issues. It can also help evaluate stress responses, sleep disorders, or hormone imbalances.

What to Expect Before the Test

No special preparation is needed for a standard cortisol blood test. If your doctor suggests a specific timing (e.g., morning or evening), follow their instructions. For a 24-hour urine test, you’ll collect urine samples over a full day.

During the Test

A healthcare provider will draw blood from a vein in your arm, or you may provide a urine sample in a collection container. The test is quick but may cause a brief pinch or discomfort.

After the Test

You can resume normal activities immediately. If you had a blood draw, apply gentle pressure to the site to stop bleeding. Report any unusual swelling, redness, or signs of infection.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

High cortisol levels may indicate overactive adrenal glands, chronic stress, or conditions like Cushing’s syndrome. Low cortisol levels could signal adrenal insufficiency, autoimmune disorders, or severe stress. Your doctor will interpret results in the context of your symptoms and medical history.

Short name

Cortisol Level

Frequently asked questions

What causes cortisol levels to be tested?
Cortisol tests are often ordered if you have symptoms like unexplained weight changes, fatigue, high blood pressure, or unusual hair growth (in Cushing’s syndrome). They may also be used to diagnose adrenal disorders, sleep apnea, or other hormonal imbalances.
How do cortisol test results differ between morning and evening?
Cortisol levels naturally rise in the morning and fall by evening. A morning test checks for early-day stress responses, while an evening test may be used to assess circadian rhythm disorders. Your doctor will specify the timing based on your suspected condition.
Can diet or medications affect cortisol test results?
Yes, certain foods, caffeine, or medications (like steroids) can temporarily alter cortisol levels. If your doctor suspects these factors, they may recommend fasting or avoiding specific substances before testing.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy