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Serum or Plasma Free Cortisol

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

This test measures the amount of cortisol (a stress hormone) that is not bound to proteins in your blood, giving a direct measure of active cortisol levels.

Quick summary

["Free cortisol helps assess how well your body regulates stress hormones and can identify issues like adrenal dysfunction."]

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

Key facts at a glance

LOINC
14253-9
Short code
GH Ab SerPl Ql
Synonyms
GH Ab SerPl Ql
Category
chemistry
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 Might Be Ordered

Your doctor may recommend this test if you have symptoms like unexplained weight changes, fatigue, or mood swings that could relate to hormonal imbalances. It’s also used in conditions like Cushing’s syndrome or Addison’s disease to confirm or monitor cortisol levels.

What to Expect Before the Test

No special preparation is needed, but if you’re taking medications that affect cortisol (like steroids), your doctor may ask you to stop them temporarily or adjust timing. Blood is drawn from a vein in your arm, similar to other blood tests.

What the Results Mean

Results help determine if your cortisol levels are too high or too low. Elevated levels might suggest overproduction of cortisol, while low levels could indicate adrenal insufficiency or other hormonal disorders.

Common Conditions Linked to Free Cortisol

High free cortisol is often linked to conditions like Cushing’s syndrome (caused by excess cortisol from tumors or medications). Low free cortisol may signal Addison’s disease (autoimmune adrenal failure) or other adrenal or pituitary disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

What triggers this test?
This test is often ordered if you have symptoms like persistent fatigue, unexplained weight gain or loss, high blood pressure, or changes in your mood or sleep patterns that doctors suspect may be linked to hormonal imbalances.
How is the blood sample collected?
A healthcare provider will insert a small needle into your arm to draw blood. You may feel a brief pinch, but it usually doesn’t cause significant discomfort. The blood is then sent to a lab for analysis.
Can I take anything special before this test?
No special preparation is required, but if you’re on medications that affect cortisol levels (like steroids), your doctor may advise you to temporarily stop them or adjust your timing. Always follow your doctor’s instructions.
  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