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Cortisol, Free (Serum/Plasma) – High-Performance Liquid Chromatography (HPLC) Measurement

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

This test measures the amount of free (unbound) cortisol in your blood, a hormone produced by your adrenal glands that helps regulate stress responses, metabolism, and immune function.

Quick summary

["Free cortisol helps assess adrenal function and potential hormone imbalances."]

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

Key facts at a glance

LOINC
12592-2
Short code
DHEA sp4 p chal SerPl-mCnc
Synonyms
DHEA sp4 p chal SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
135
Ref high
980
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82626
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 healthcare provider may recommend this test if you have symptoms like unexplained weight changes, fatigue, high blood pressure, or signs of hormonal disorders. It could also be used to evaluate conditions like Cushing’s syndrome, adrenal insufficiency, or to monitor treatment for hormone-related disorders.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood draw at your doctor’s office or a lab. If you’re taking medications that affect cortisol levels, let your provider know.

What the Results Mean

Free cortisol levels can vary based on your body’s natural rhythms and stress levels. Your results will be compared to standard reference ranges provided by your lab to determine if your levels are within normal limits or if further evaluation is needed.

Common Conditions This Test Helps Diagnose

This test is often used to diagnose or monitor conditions such as Cushing’s syndrome (too much cortisol), adrenal insufficiency (too little cortisol), or to check for hormonal imbalances that may affect your health.

Reference range

NCBI: DHEA-S Male 135-980 µg/dL; Female 30-260 µg/dLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Cortisol

Frequently asked questions

What Does ‘Free Cortisol’ Mean?
‘Free cortisol’ refers to the cortisol that is not bound to proteins in your blood. Only the free (unbound) portion can actually enter cells and exert its effects. Measuring free cortisol helps avoid false results from protein-bound cortisol that might not be biologically active.
How Is Cortisol Measured Differently from Total Cortisol?
Total cortisol includes both free and protein-bound cortisol, while free cortisol only measures the active, unbound portion. Free cortisol testing is often preferred for more accurate assessment of adrenal function, especially in conditions where protein binding might interfere with results.
Can Stress Affect My Cortisol Levels?
Yes, stress—whether physical, emotional, or from illness—can temporarily raise cortisol levels. If you’re under significant stress before your test, your results may not reflect your baseline cortisol levels. Your provider may recommend testing at a specific time (e.g., morning) to minimize this effect.
  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