Skip to content

Cortisol, Free (Serum/Plasma)

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

This test measures the amount of free cortisol, a form of the hormone cortisol that circulates freely in your blood. Free cortisol is important for regulating stress responses, metabolism, and other bodily functions.

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
9612-3
Short code
Cortis 15M p 250 ug ACTH IM SerPl-mCnc
Synonyms
Cortis 15M p 250 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 Is This Test Done?

Your doctor may order a free cortisol test to check for conditions like Cushing’s syndrome (when your body makes too much cortisol) or adrenal insufficiency (when your adrenal glands don’t produce enough cortisol). It can also help diagnose issues with your pituitary gland or adrenal glands, which control hormone production.

What Does the Test Involve?

A blood sample is taken from a vein in your arm. You may feel a small pinch when the needle goes in, but the process usually takes only a few minutes. The sample is sent to a lab for analysis.

What to Expect Before or After the Test

No special preparation is usually needed, but if you’re taking certain medications (like steroids), your doctor may advise adjusting your timing or dosage. After the test, you may experience mild bruising or soreness at the injection site, which typically goes away quickly.

How Is the Test Performed?

The test uses a specialized immunoassay method to detect cortisol in your blood. This method is highly sensitive and accurate, ensuring reliable results for diagnosing hormonal imbalances.

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

Why might my doctor ask for this test?
Your doctor may recommend this test if you have symptoms like unexplained weight changes, fatigue, high blood pressure, or changes in your mood or energy levels. It’s also used to monitor conditions like Cushing’s syndrome or Addison’s disease.
What are the normal ranges for this test?
There is no single standard range for free cortisol because it can vary based on factors like time of day, stress levels, and individual health. Your doctor will use the results along with other tests and your symptoms to determine what’s normal for you.
Can I eat or drink before the test?
You can typically eat and drink normally before the test unless your doctor specifies otherwise. Avoiding caffeine or stress-inducing activities for a few hours before the test may help ensure more 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 17, 2026. · Read our editorial policy