Cortisol-Free Serum Test
About Cortisol-Free Serum Test
| Field | Value |
|---|---|
| Also Known As | Free cortisol test, serum free cortisol test, unbound cortisol test, free serum cortisol test |
| Sample Type | Serum (venous blood) |
| Fasting Required | Generally not required; timing of collection matters more than fasting |
| Report Time | 23 Days |
| Recommended For | Adults and children of all ages; males and females |
| Price | Starting at ₹7,800 |
What Is a Cortisol-Free Serum Test?
The cortisol-free serum test measures the biologically active portion of cortisol in your blood. Most cortisol in the bloodstream is bound to proteins and inactive. Only the small, unbound fraction known as free cortisol can act on tissues and influence how the body responds to stress and regulates metabolism. Doctors order this test when standard total cortisol results may be unreliable, such as in patients with known protein-binding abnormalities or in critically ill individuals. It is also called the free cortisol test or serum free cortisol test.
What Does a Cortisol-Free Serum Test Measure?
This test specifically isolates and quantifies the unbound fraction of cortisol circulating in the blood. The table below explains what is assessed.
| Parameter | What It Tells Us |
|---|---|
| Free cortisol (baseline, morning) | The active, unbound cortisol level at the body's natural daily peak |
| Free cortisol at 30 minutes (ACTH stimulation, if applicable) | How the adrenal glands respond to stimulation at 30 minutes |
| Free cortisol at 60 minutes (ACTH stimulation, if applicable) | Adrenal response at 60 minutes, used to rule out adrenal insufficiency |
Normally, less than 5% of total circulating cortisol is free. This fraction is what enters cells and drives the hormone's effects on the body.
Why is a Cortisol-Free Serum Test Done?
A doctor may request this test for several reasons, from evaluating unexplained symptoms to monitoring a known adrenal condition.
Common Symptoms That May Require This Test
The following symptoms may prompt a doctor to order a cortisol-free test:
- Unexplained weight loss or significant weight gain
- Persistent, extreme tiredness that does not improve with rest
- Muscle and joint pain without a clear cause
- Low blood pressure or dizziness when standing up
- Nausea, vomiting, or abdominal discomfort
- Darkening of the skin (hyperpigmentation)
- Loss of body hair or poor appetite
Conditions This Test Can Help Detect
The unbound cortisol test can help identify a range of adrenal and hormonal conditions, including:
- Cushing syndrome, where the body produces too much cortisol
- Addison's disease (primary adrenal insufficiency), where cortisol is too low
- Secondary adrenal insufficiency, caused by pituitary gland problems
- Abnormalities in cortisol-binding proteins due to kidney or liver disease
- Assessment of adrenal function in critically ill patients
Cortisol-Free Serum Test for Chronic Disease Monitoring
This test is often repeated over time to track how well treatment is working. Patients with Addison's disease receiving hormone replacement therapy may have their free cortisol checked at regular intervals to ensure their levels remain stable. Similarly, individuals being treated for Cushing syndrome may undergo periodic testing to confirm that cortisol levels are returning to a healthy range.
How to Prepare and What to Expect
Preparing correctly for this test helps ensure your results are as accurate as possible.
Do You Need to Fast?
Fasting is generally not required for this test. Timing your blood draw correctly, typically in the morning, is more important than skipping meals. If your doctor has also ordered an ACTH stimulation test alongside this one, fasting for six hours beforehand may be required. Confirm the instructions with your doctor or the collection team.
Practical Tips Before Your Test
Keep the following points in mind before your appointment:
- Schedule your sample collection in the morning, ideally between 6 AM and 10:30 AM, when cortisol levels are at their natural peak.
- Bring a detailed clinical history, including your symptoms, previous test results, and family history, as this is required for the test.
- Stop taking biotin (vitamin B7) supplements at least 72 hours before sample collection.
- Inform your doctor about all medications you are currently taking, including corticosteroids and oral contraceptives, as these can affect results.
- Avoid vigorous exercise the day before the test.
- Stay well hydrated; drink plenty of water.
Step-by-Step Procedure
Here is what to expect during your cortisol-free serum test appointment:
- Arrive at the collection point or welcome the home collection phlebotomist in the morning, within the recommended time window.
- The phlebotomist will clean the skin over a vein in your arm or hand using an antiseptic swab.
- A small needle is inserted into the vein, and approximately 3 ml of blood is drawn into a yellow-top gel tube. The process typically takes five to ten minutes.
- Once collected, the sample is stored under refrigeration between 2 and 8 degrees Celsius to preserve its integrity.
- The sample is sent to the laboratory, where the unbound cortisol fraction is carefully separated and measured using an EIA (enzyme immunoassay) method.
- Your report is prepared and delivered digitally within the turnaround period.
Factors That Can Affect Accuracy
Several factors can influence your cortisol-free test results:
- Collecting the sample outside the recommended morning window
- High stress levels or poor sleep in the days before the test
- Certain medications, particularly corticosteroids, oestrogen therapy, and oral contraceptives.
- Significant kidney or liver disease, which alters protein-binding levels
- Recent intense physical activity
- Not disclosing biotin supplement use before the test
Understanding Your Cortisol-Free Serum Test Results
Your free serum cortisol test results should always be reviewed alongside your full clinical picture. The table below shows general reference ranges for this test.
| Parameter | Reference Range | Unit |
|---|---|---|
| Free cortisol at baseline (6:00 AM to 9:00 AM) | 10 to 20 | mcg/dL |
| Free cortisol at 30 minutes (ACTH stimulation) | greater than or equal to 18 | mu g/dL |
| Free cortisol at 60 minutes (ACTH stimulation) | 18 to 20 | mu g/dL |
| Total cortisol (morning, 6 to 8 AM) | 10 to 20 | mcg/dL |
| Total cortisol (around 4 PM) | 3 to 10 | mcg/dL |
Disclaimer: These ranges are general guidelines. Your doctor will interpret your results based on your age, health history, and other factors. Always consult a qualified healthcare professional for personalised medical advice.
Results During Special Conditions
Certain health conditions can alter how results are interpreted:
- Kidney disease, particularly nephrotic syndrome, can cause loss of cortisol-binding globulin (CBG) in the urine, which may cause total cortisol to appear falsely low and lead to an incorrect diagnosis of adrenal insufficiency. Free cortisol testing is more reliable in these cases.
- Liver disease, hyperthyroidism, and alcohol dependence are associated with lower CBG levels, which also affect total cortisol measurements. Free cortisol testing provides a clearer picture of true hormone activity in these patients.
- Pregnancy and oestrogen-based contraceptives raise CBG levels twofold to threefold, increasing total cortisol readings. This oestrogen-driven effect alters how the body manages and transports cortisol, which has important clinical implications for hormone testing and glucose regulation.
How to Maintain Healthy Levels
The following general lifestyle habits support balanced cortisol levels:
- Practise stress management techniques such as mindfulness, breathing exercises, or yoga, and aim for seven to nine hours of sleep each night.
- Eat a balanced diet and limit excessive caffeine and alcohol consumption.
- Follow your healthcare provider's guidance on any medications or supplements that may affect your hormone levels.
Lupin Diagnostics Cortisol-Free Serum Test Price and Home Collection
The Cortisol-Free Serum test is available at Lupin Diagnostics, starting at ₹7,800, with home sample collection offered across cities. The table below lists indicative prices by city.
| City | Approximate Price ( ₹) |
|---|---|
| BHOPAL | 7800 |
| CHENNAI | 7800 |
| HYDERABAD | 7800 |
| KOLKATA | 7800 |
| NAVI MUMBAI | 7800 |
| PUNE | 7800 |
Disclaimer: Prices are indicative and may vary by location. Please confirm the current price at the time of booking.
How to Book
Follow these steps to book your cortisol-free test online:
- Select the test on the Lupin Diagnostics website.
- Choose your city and preferred time slot.
- Opt for home sample collection by a certified phlebotomist, or visit your nearest Lupin Diagnostics centre.
- Receive your report via email or WhatsApp within the stipulated turnaround time.
Home Collection
Cortisol-Free test home collection is available across multiple cities. A trained phlebotomist will visit your home at a convenient morning slot to collect the sample. All samples are processed in NABL-accredited laboratories, and your digital report is delivered securely via email or WhatsApp.
Frequently Asked Questions
Total cortisol includes both the protein-bound and unbound portions circulating in your blood. Free cortisol is only the unbound portion, which makes up less than 5% of the total. Free cortisol is the biologically active form that enters cells and carries out the hormone's functions. The cortisol-free serum test specifically measures this active fraction.
Cortisol levels follow a natural daily rhythm, peaking between 6 AM and 8 AM and reaching their lowest point around midnight. Collecting the sample in the morning captures this peak and gives your doctor the most meaningful baseline reading. Collecting outside this window can make results difficult to interpret.
Yes. Corticosteroids, oral contraceptives, oestrogen therapy, and certain other medications can raise or lower cortisol readings. Biotin supplements can also interfere with the test, so you should stop taking them at least 72 hours before collection. Always tell your doctor about every medication and supplement you take.
The cortisol-free test is particularly useful when protein-binding abnormalities are suspected, for example, in patients with kidney disease, liver disease, or those taking oestrogen therapy. It is also preferred for assessing adrenal function in critically ill patients, where standard total cortisol measurements may be misleading.
Yes. A detailed clinical history is required when submitting your sample for this test. Please bring information about your current symptoms, any previous test results, relevant medical history, and a list of medications you are taking.
Pregnancy raises the level of cortisol-binding globulin in the blood, which increases total cortisol readings. However, this does not increase the free, biologically active cortisol fraction. Measuring free cortisol can therefore provide a more accurate assessment of adrenal function in pregnant women compared to a standard total cortisol test.
If your free serum cortisol results fall outside the normal range, your doctor may order further tests to identify the underlying cause. These may include an ACTH stimulation test, 24-hour urinary free cortisol, midnight salivary cortisol, or a dexamethasone suppression test. Your doctor will decide which tests are appropriate based on your symptoms and clinical history.
Cortisol-Free Serum Test
