What is Percent Free Cortisol?
Percent Free Cortisol, Serum refers to the proportion of cortisol in your blood that is not attached to proteins such as corticosteroid-binding globulin (CBG) or albumin. While about 90–95% of circulating cortisol is bound to these proteins and biologically inactive, the remaining 5–10% is “free” and able to enter cells, where it triggers important physiological effects-including the stress response, metabolism regulation, and immune system modulation.
Why is Percent Free Cortisol Important?
Most standard cortisol tests measure total cortisol, which includes both bound (inactive) and free (active) forms. However, only free cortisol is immediately available for your body to use. Measuring the percentage of free cortisol (rather than just the total or absolute free cortisol level) provides insight into how much of your cortisol is active versus stored. This is particularly important in situations where the levels of binding proteins change, such as during pregnancy, liver disease, or with certain medications, which can make total cortisol results misleading.
Calculating percent free cortisol-or using related indices like the Free Cortisol Index (total cortisol divided by CBG)-can reveal subtle imbalances in adrenal function that may not show up in standard tests.
Note: Direct measurement of free cortisol in blood is technically challenging and not always available. Sometimes, percent free cortisol is calculated based on total cortisol and binding protein levels. Salivary cortisol is also used as a noninvasive surrogate for free cortisol in some settings.
What Does a High Percent Free Cortisol Mean?
An elevated percent free cortisol can indicate:
-
Reduced cortisol-binding proteins: Seen in liver disease or high estrogen states (e.g., pregnancy).
-
Increased cortisol production: Such as from chronic stress or Cushing’s syndrome.
-
Overuse of corticosteroid medications: Which can disrupt normal cortisol regulation.
What Does a Low Percent Free Cortisol Mean?
A low value may suggest:
-
Increased levels of cortisol-binding globulin: This reduces the free fraction, and is seen with estrogen therapy or oral contraceptive use.
-
Adrenal insufficiency or reduced cortisol production: The adrenal glands are not making enough cortisol.
-
Certain inflammatory or autoimmune conditions: These can affect cortisol availability or binding.
Clinical Use
Percent free cortisol testing is especially helpful when total cortisol results do not match a patient’s symptoms. It may be ordered during investigations of:
-
Adrenal disorders (like Addison’s disease or Cushing’s syndrome)
-
Unexplained fatigue or weakness
-
Abnormal stress responses
-
Situations where binding protein levels are altered (e.g., pregnancy, liver disease, critical illness)
Summary Table
| Aspect | Bound Cortisol (CBG + Albumin) | Free Cortisol (Percent Free) |
|---|---|---|
| Fraction of total | 90–95% | 5–10% |
| Biological activity | Inactive | Active (enters cells, exerts effects) |
| Affected by protein changes | Yes | No |
| Clinical relevance | May mislead in illness, pregnancy | Reflects true adrenal function |
In summary: Measuring percent free cortisol helps provide a more accurate picture of your adrenal health, especially when total cortisol levels are difficult to interpret due to changes in binding proteins or unusual clinical situations.
What does it mean if your Percent Free Cortisol, Serum result is too high?
What Does Elevated Percent Free Cortisol Mean?
An elevated level of free or percent free cortisol indicates that more biologically active cortisol is circulating in the body. This can have various clinical implications depending on the context:
Common Causes of Elevated Free Cortisol
-
Chronic Stress: Persistent psychological or physical stress activates the hypothalamic-pituitary-adrenal (HPA) axis, increasing cortisol production to help the body cope with ongoing demands.
-
Cushing’s Syndrome or Disease: Excessively high free cortisol is a hallmark of Cushing’s syndrome, often due to a pituitary tumor (Cushing’s disease), adrenal tumor, or ectopic ACTH production.
-
Adrenal or Pituitary Tumors: Tumors in these glands may drive excessive cortisol secretion, contributing to elevated free cortisol levels.
-
Medication Effects: Corticosteroid use can elevate free cortisol directly. Estrogen-containing medications (like oral contraceptives or hormone therapy) may increase free cortisol indirectly by altering cortisol-binding protein levels.
-
Physiological States: Pregnancy, severe infection, and critical illness can raise free cortisol due to shifts in hormone production and changes in binding protein concentrations.
-
Obesity and Hyperthyroidism: In obesity, increased cortisol clearance may lead to compensatory overproduction. Hyperthyroidism can accelerate cortisol metabolism, influencing free cortisol levels.
Symptoms and Potential Health Risks
Chronic elevation of free cortisol can lead to a range of symptoms and complications, including:
-
Central weight gain (especially around the face and abdomen)
-
Acne and skin thinning
-
Muscle weakness and persistent fatigue
-
Elevated blood pressure
-
Mood disturbances, such as irritability or poor concentration
-
Increased cardiovascular risk (e.g., heart attack, stroke)
Special Considerations
-
In critical illness or sepsis, high free cortisol often reflects a heightened stress response and may correlate with disease severity or poor prognosis.
-
Elevated levels may also occur due to decreased cortisol-binding proteins, such as in liver disease, without an actual increase in cortisol production.
In Summary
Elevated free or percent free cortisol typically reflects an overactive stress response, a hormonal disorder like Cushing’s, medication influence, or altered cortisol metabolism. Persistent elevation warrants further evaluation to identify the underlying cause and manage potential health risks.
All Your Lab Results.
One Simple Dashboard.
Import, Track, and Share Your Lab Results Easily
Import, Track, and Share Your Lab Results
Import lab results from multiple providers, track changes over time, customize your reference ranges, and get clear explanations for each result. Everything is stored securely, exportable in one organized file, and shareable with your doctor—or anyone you choose.
Cancel or upgrade anytime
Laboratories
Bring All Your Lab Results Together — In One Place
We accept reports from any lab, so you can easily collect and organize all your health information in one secure spot.
Pricing Table
Gather Your Lab History — and Finally Make Sense of It
Finally, Your Lab Results Organized and Clear
Personal plans
$79/ year
Advanced Plan
Access your lab reports, explanations, and tracking tools.
- Import lab results from any provider
- Track all results with visual tools
- Customize your reference ranges
- Export your full lab history anytime
- Share results securely with anyone
- Receive 5 reports entered for you
- Cancel or upgrade anytime
$250/ once
Unlimited Account
Pay once, access everything—no monthly fees, no limits.
- Import lab results from any provider
- Track all results with visual tools
- Customize your reference ranges
- Export your full lab history anytime
- Share results securely with anyone
- Receive 10 reports entered for you
- No subscriptions. No extra fees.
$45/ month
Pro Monthly
Designed for professionals managing their clients' lab reports
- Import lab results from any provider
- Track lab results for multiple clients
- Customize reference ranges per client
- Export lab histories and reports
- Begin with first report entered by us
- Cancel or upgrade anytime
About membership
What's included in a Healthmatters membership
Import Lab Results from Any Source
See Your Health Timeline
Understand What Your Results Mean
Visualize Your Results
Data Entry Service for Your Reports
Securely Share With Anyone You Trust
Let Your Lab Results Tell the Full Story
Once your results are in one place, see the bigger picture — track trends over time, compare data side by side, export your full history, and share securely with anyone you trust.
Bring all your results together to compare, track progress, export your history, and share securely.
What Healthmatters Members Are Saying
Frequently asked questions
Healthmatters is a personal health dashboard that helps you organize and understand your lab results. It collects and displays your medical test data from any lab in one secure, easy-to-use platform.
- Individuals who want to track and understand their health over time.
- Health professionals, such as doctors, nutritionists, and wellness coaches, need to manage and interpret lab data for their clients.
With a Healthmatters account, you can:
- Upload lab reports from any lab
- View your data in interactive graphs, tables, and timelines
- Track trends and monitor changes over time
- Customize your reference ranges
- Export and share your full lab history
- Access your results anytime, from any device
Professionals can also analyze client data more efficiently and save time managing lab reports.
Healthmatters.io personal account provides in-depth research on 10000+ biomarkers, including information and suggestions for test panels such as, but not limited to:
- The GI Effects® Comprehensive Stool Profile,
- GI-MAP,
- The NutrEval FMV®,
- The ION Profile,
- Amino Acids Profile,
- Dried Urine Test for Comprehensive Hormones (DUTCH),
- Organic Acids Test,
- Organix Comprehensive Profile,
- Toxic Metals,
- Complete Blood Count (CBC),
- Metabolic panel,
- Thyroid panel,
- Lipid Panel,
- Urinalysis,
- And many, many more.
You can combine all test reports inside your Healthmatters account and keep them in one place. It gives you an excellent overview of all your health data. Once you retest, you can add new results and compare them.
If you are still determining whether Healthmatters support your lab results, the rule is that if you can test it, you can upload it to Healthmatters.
We implement proven measures to keep your data safe.
At HealthMatters, we're committed to maintaining the security and confidentiality of your personal information. We've put industry-leading security standards in place to help protect against the loss, misuse, or alteration of the information under our control. We use procedural, physical, and electronic security methods designed to prevent unauthorized people from getting access to this information. Our internal code of conduct adds additional privacy protection. All data is backed up multiple times a day and encrypted using SSL certificates. See our Privacy Policy for more details.