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Cortisol (serum/plasma) 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 manage stress and supports normal bodily functions."]

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

Key facts at a glance

LOINC
16671-0
Short code
Cortis 1M p chal SerPl-mCnc
Synonyms
Cortis 1M p chal SerPl-mCnc
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

Your doctor may order cortisol testing to check for conditions like Cushing’s syndrome (too much cortisol), Addison’s disease (too little cortisol), or to evaluate adrenal gland function. It can also help diagnose hormonal imbalances or assess responses to stress or medications.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if timing your cortisol levels around certain times of day is important. Bring any medications you’re taking to your appointment.

During the Test

A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause discomfort. The blood sample is sent to a lab for analysis.

After the Test

You can resume normal activities immediately. Apply gentle pressure to the injection site to stop any bleeding, and check for signs of infection (redness, swelling, or fever) over the next few days. Report any unusual symptoms to your doctor.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormal cortisol levels can indicate serious conditions. High cortisol may suggest Cushing’s syndrome, chronic stress, or certain tumors. Low cortisol could signal Addison’s disease, pituitary issues, or adrenal failure. Your doctor will interpret results in the context of your symptoms and medical history.

Short name

Cortisol Level

Frequently asked questions

How is cortisol measured?
Cortisol is measured using a blood sample taken from your vein. The test typically uses an immunoassay method to detect and quantify cortisol in your serum or plasma.
What are typical reference ranges?
Reference ranges vary by lab and testing method. Your doctor will provide your specific results and compare them to your body’s needs, not a fixed range.
Can cortisol levels change with diet or exercise?
Yes, cortisol fluctuates naturally throughout the day, peaking in the morning and dropping at night. Stress, sleep, and certain medications can also affect levels. Your doctor may recommend testing at specific times for accuracy.
  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