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Serum/plasma mass concentration of free cortisol

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

This test measures the amount of free (unbound) cortisol in your blood, which helps assess cortisol levels independent of proteins that normally carry cortisol in the blood.

Quick summary

["Free cortisol helps diagnose 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
47891-7
Short code
GH 15M p GRF SerPl-aCnc
Synonyms
GH 15M p GRF SerPl-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
86430
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 Is This Test Done?

Your healthcare provider may order this test if you have symptoms like unexplained weight gain, fatigue, high blood pressure, or unusual hair growth, which can be linked to abnormal cortisol levels. It may also be used to monitor conditions like Cushing’s syndrome or Addison’s disease.

What Does the Result Mean?

Results are not provided as a specific range here, but elevated or low levels may indicate hormonal imbalances. Your doctor will interpret the result in the context of your symptoms and other tests.

How Is the Sample Collected?

A blood sample is drawn from a vein, usually in your arm. You may feel a small pinch when the needle is inserted, but the process is quick. You can eat and drink normally before the test unless instructed otherwise.

What Should I Expect Before the Test?

No special preparation is needed, but inform your doctor about any medications, especially steroids, that you’re taking. Avoid alcohol for 24 hours before testing if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Free cortisol is critical for diagnosing conditions like Cushing’s syndrome (excess cortisol) or adrenal insufficiency (low cortisol). It helps rule out hormonal disorders affecting metabolism, stress response, and immune function.

Short name

Free Cortisol

Frequently asked questions

What causes abnormal free cortisol levels?
Abnormal results may be due to conditions like Cushing’s syndrome (from tumors or excess steroid use), Addison’s disease (adrenal gland failure), or pituitary disorders. Stress, medications, or genetic factors can also influence cortisol levels.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will contact you with the final report.
Can I eat or drink before this test?
You can eat and drink normally unless your doctor specifies otherwise. Avoid alcohol for 24 hours before testing to ensure accurate results.
  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