Description of blood Analysis: 

Serum Free Cortisol measures the fraction of cortisol that is not bound to proteins (such as Corticosteroid-Binding Globulin or Albumin) in the blood. While the vast majority of circulating cortisol is protein-bound and inactive, “free” cortisol is the biologically active form capable of entering cells and exerting physiological effects. In clinical diagnostics, this test is particularly valuable when protein levels are altered—due to pregnancy, oral contraceptive use, or liver and kidney diseases—situations where a “Total Cortisol” test may be misleading. By measuring the free fraction, physicians get a direct look at the amount of hormone actually available to the body’s tissues to regulate metabolism and the stress response.

What does the analysis represent?

• Purpose: To quantify the biologically active, unbound fraction of cortisol in the bloodstream.
• Primary Application: Investigating adrenal dysfunction (Cushing’s syndrome or Addison’s disease) in patients with abnormal protein levels and assessing “critical illness-related corticosteroid insufficiency” (CIRCI).
• Method: Equilibrium dialysis (gold standard) or calculation based on Total Cortisol and Binding Proteins.

Recommendations for the Test (General)

• Timing: Typically performed in the morning (7:00 AM – 9:00 AM) to align with the peak of the diurnal rhythm.
• Fasting: A 12-hour fast is required; water is permitted.
• Rest: Minimize physical activity and emotional stress for 24 hours before the test, as these factors immediately stimulate cortisol release.
• Specific Rules: Refrain from alcohol and caffeine for 24 hours prior. Inform your doctor of any steroid-based medications (including creams or inhalers) you are using.

What can affect the results?

• Factors altering levels: Severe physical stress (surgery, trauma), acute infection, and severe systemic illness can cause a dramatic rise in free cortisol.
• Conversely: Use of synthetic glucocorticoids can suppress the body’s natural production, leading to low results.

When to take the test?

• Recommendations: This test is recommended when Total Cortisol results are inconsistent with clinical symptoms, especially in patients with altered protein status (e.g., during pregnancy or in cases of nephrotic syndrome).
• Preparation: The test should be scheduled when the patient is in a stable clinical state unless being used to evaluate an acute stress response in a hospital setting.

How to interpret the results?

• The interpretation of your laboratory results is the exclusive responsibility of a qualified physician.
• A Serum Free Cortisol value must be interpreted in light of the patient’s clinical condition and the presence of any protein-altering factors.
• Only a professional medical review can integrate these findings with your history to determine if the adrenal output is appropriate for your body’s needs.

Possible further investigations

• CBG (Corticosteroid-Binding Globulin) Test: To understand the transport capacity for cortisol.
• 24-Hour Urinary Free Cortisol: To provide an integrated measure of daily free hormone excretion.
• Salivary Cortisol (Late Night): To check the integrity of the diurnal rhythm.
• Endocrinology Consultation: To evaluate complex adrenal or pituitary disorders.

When does the next step make sense?

• If free cortisol levels are found to be abnormal, the findings are reviewed by a physician to determine the necessity of dynamic suppression or stimulation tests.
• All medical decisions are personalized based on the patient’s overall physiological status.

👉 If necessary, you can discuss the analysis results with a specialist such as an endocrinologist (Doctors – TAMC).