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Serum Free Cortisol (Mass Concentration)

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

This test measures the amount of free (unbound) cortisol in your blood, a key hormone involved in stress response and metabolism.

Quick summary

["Free cortisol helps doctors assess adrenal function and rule out conditions like Cushing’s syndrome or adrenal insufficiency."]

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

Key facts at a glance

LOINC
46397-6
Short code
Cortis 15M p 1 ug/kg CRH IV SerPl-mCnc
Synonyms
Cortis 15M p 1 ug/kg CRH IV 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
CPT
86701
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 this test if you have symptoms like unexplained weight changes, fatigue, high blood pressure, or unusual mood swings. It’s also used to diagnose or monitor conditions affecting cortisol levels, such as hormonal imbalances or certain cancers.

What to Expect Before the Test

No special preparation is needed, but you may be asked to avoid certain medications (like some steroids) that could affect results. Bring a list of all current medications to your appointment.

How the Test Works

A blood sample is taken from a vein in your arm. The sample is processed to measure free cortisol levels, which are then compared to standard reference ranges.

What the Results Mean

Results help determine if your cortisol levels are too high (hypercortisolism) or too low (hypocortisolism). Abnormal levels may indicate conditions requiring further medical evaluation or treatment.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Free Cortisol

Frequently asked questions

How often do I need this test?
This test may be repeated based on your symptoms or treatment plan, such as every few months for monitoring or as needed for diagnostic follow-up.
Can diet or exercise affect cortisol levels?
Diet, stress, and exercise can influence cortisol, so your doctor may ask you to avoid extreme changes before testing or note any recent stressors.
What if my results are out of range?
If results are abnormal, your doctor will discuss next steps, which may include additional tests, lifestyle adjustments, or treatment to restore balance.
  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