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Cortisol, Free, Serum

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of free cortisol, a naturally occurring steroid hormone produced by your adrenal glands. Free cortisol is the active form that circulates in your bloodstream and helps regulate metabolism, immune response, and stress reactions.

Quick summary

["Free cortisol helps your body manage stress and maintain balance in your hormones."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
1413-4
Short code
Cortis 2D p 500 ug ACTH IM SerPl-mCnc
Synonyms
Cortis 2D p 500 ug ACTH IM SerPl-mCnc
Category
hormone
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
60
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 Might Be Ordered

Your doctor may recommend this test if they suspect conditions like Cushing’s syndrome (overactive adrenal glands), adrenal insufficiency (underactive adrenal glands), or other hormonal imbalances. It can also be used to monitor treatment for conditions affecting cortisol levels, such as certain medications or chronic stress.

What to Expect Before the Test

No special preparation is needed for this test. You’ll have a small needle inserted into your arm to draw blood. If you’re taking medications that affect cortisol levels (like steroids), let your doctor know before the test.

What the Results Mean

Free cortisol levels can vary based on your time of day, stress levels, and overall health. Your doctor will interpret the results in relation to your symptoms and other tests. Abnormal results may indicate hormonal disorders or other health concerns.

Common Conditions Linked to Free Cortisol Levels

High cortisol levels might be linked to conditions like Cushing’s syndrome, excessive stress, or certain tumors. Low cortisol levels could suggest adrenal insufficiency, autoimmune disorders, or long-term steroid use.

Reference range

NCBI: ACTH 10-60 pg/mLN/A

Specimen: serum

Typically collected in the morning (8-10 AM). Inform your provider if taking steroid medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

What causes false high or low cortisol results?
False high results may occur due to recent stress, certain medications (like steroids), or improper sample handling. False low results could happen if you didn’t fast before the test (though fasting isn’t required here) or if cortisol was degraded during storage.
How often should I get this test?
Your doctor will determine how often you need retests based on your symptoms, treatment plan, or ongoing health concerns. Follow their guidance—don’t schedule it without checking in first.
Can I drink coffee or eat before this test?
No, you don’t need to fast or avoid coffee. However, inform your doctor about any medications, supplements, or recent stress that might affect cortisol levels.
  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 17, 2026. · Read our editorial policy