Cortisol Free 24 Hour Urine Biomarker Testing
It measures your total free cortisol output over 24 hours to assess cortisol excess or suppression, with easy ordering and Quest collection via Vitals Vault.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
A Cortisol Free 24 Hour Urine test measures how much “free” (unbound, biologically active) cortisol your body releases over an entire day. Because cortisol naturally rises and falls across the day, a single blood or saliva value can miss patterns that show up when you look at total daily output.
This test is most often used when you and your clinician are trying to rule out cortisol excess (such as Cushing syndrome) or understand whether medications or medical conditions are suppressing cortisol production. It can also be used to monitor treatment when cortisol levels have been high.
The result is only as good as the collection. If the 24-hour urine is incomplete, the number can look falsely low, so the “how” matters as much as the “what.”
Do I need a Cortisol Free 24 Hour Urine test?
You may want this test if you have signs that raise concern for cortisol excess, especially when symptoms cluster and persist. Examples include unexplained weight gain (often around the abdomen), easy bruising, new or worsening high blood pressure or blood sugar, muscle weakness, or purple stretch marks. Your clinician may also consider it if you have osteoporosis at a younger age or recurrent infections without a clear reason.
This test can also be useful if you are taking glucocorticoid medications (such as prednisone, certain steroid injections, or high-potency steroid creams) and there is a question of cortisol suppression or medication-related effects. In those cases, your clinician may choose different testing depending on your situation, but urinary free cortisol can be part of the workup.
You might not need a 24-hour urine cortisol if your main goal is to understand day-to-day stress patterns or sleep-related cortisol timing. Those questions are often better answered with timed saliva or blood testing rather than a total 24-hour output.
Testing is meant to support clinician-directed care and diagnosis. A single result rarely tells the whole story, so it is usually interpreted alongside your symptoms, medications, and follow-up testing when needed.
This is a CLIA-certified laboratory test; results are for education and clinical discussion and are not a standalone diagnosis.
Lab testing
Order Cortisol Free 24 Hour Urine through Vitals Vault when you’re ready to test or retest.
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
If you are trying to make sense of symptoms or you already have an abnormal cortisol result, Vitals Vault lets you order Cortisol Free 24 Hour Urine testing without waiting for a separate lab referral. You complete the 24-hour collection at home and drop it off according to the lab’s instructions.
Once your result is back, PocketMD can help you translate the number into next-step questions for your clinician, such as whether the collection was adequate, whether repeat testing is appropriate, and which companion tests commonly clarify the picture.
If follow-up is needed, you can reorder the same test to confirm a pattern or add related labs through Vitals Vault so your clinician has a more complete dataset to work with.
- Order online and use a national lab network for specimen handling
- PocketMD helps you prepare questions and interpret results in context
- Easy retesting when your clinician recommends confirmation
Key benefits of Cortisol Free 24 Hour Urine testing
- Captures total daily free cortisol output, reducing the noise of normal hour-to-hour swings.
- Helps screen for cortisol excess when symptoms suggest Cushing syndrome or related conditions.
- Supports treatment monitoring when cortisol has been high and you need objective trend data.
- Can reveal medication-related effects when steroid exposure is suspected or being tapered.
- Pairs well with other cortisol tests to confirm whether an abnormal result is consistent.
- Highlights collection quality issues (for example, incomplete collection) that can change interpretation.
- Gives you a concrete result you can review with PocketMD and your clinician to plan next steps.
What is Cortisol Free 24 Hour Urine?
Cortisol is a steroid hormone made by your adrenal glands that helps regulate blood sugar, blood pressure, immune activity, and your response to physical and emotional stress. In blood, most cortisol is bound to proteins, while a smaller portion is “free” and active.
A 24-hour urinary free cortisol (UFC) test measures the amount of free cortisol your kidneys filter and excrete into urine over a full day. Because it sums cortisol output across 24 hours, it is often used to evaluate sustained cortisol overproduction rather than short-lived spikes.
Clinicians commonly use this test as part of a Cushing syndrome evaluation. It is not perfect on its own, so abnormal results are typically confirmed with repeat testing and/or another first-line test (such as late-night salivary cortisol or an overnight dexamethasone suppression test).
Why 24 hours matters
Cortisol follows a circadian rhythm: it is usually higher in the morning and lower at night. A single blood draw can be normal even when total daily output is high, or abnormal because of timing. A complete 24-hour urine collection smooths out timing effects by measuring the full day’s excretion.
What “free” means here
“Free” cortisol in urine reflects unbound cortisol that was filtered by the kidneys. It is less affected by changes in cortisol-binding proteins than some blood measurements, but it can still be influenced by kidney function, urine volume, and collection accuracy.
What do my Cortisol Free 24 Hour Urine results mean?
Low urinary free cortisol
A low result can happen if your body is producing less cortisol than expected, but it can also occur when the 24-hour collection is incomplete (for example, missed voids). True low cortisol output may be seen with adrenal insufficiency or suppression from glucocorticoid medications. If your symptoms include severe fatigue, dizziness, low blood pressure, or low sodium, your clinician may prioritize blood testing such as morning serum cortisol and ACTH (adrenocorticotropic hormone) and consider an ACTH stimulation test.
In-range urinary free cortisol
An in-range result suggests your total daily free cortisol output is not elevated at the time of testing. If you were being evaluated for cortisol excess, this can be reassuring, but it does not always fully rule it out because cortisol production can be variable. If suspicion remains high, clinicians often repeat the test and/or use a different method that captures nighttime cortisol or suppression response.
High urinary free cortisol
A high result means your body excreted more free cortisol than the lab’s reference range over 24 hours. This can be seen in Cushing syndrome, but it can also occur with severe physiologic stress, uncontrolled diabetes, depression, alcohol overuse, or certain medications. Because false positives are possible, clinicians usually confirm with repeat UFC and another first-line test before moving to imaging or more specialized hormone testing.
Factors that influence urinary free cortisol
Collection quality is the biggest factor: missing urine during the 24-hour window can make results falsely low, while collecting longer than 24 hours can inflate the value. Kidney function and very high or very low urine volume can change excretion patterns. Medications matter, especially any form of steroid (pills, injections, inhalers, nasal sprays, or creams), estrogen therapy, and some anti-seizure drugs; always list what you take on the requisition or with your clinician. Acute illness, sleep disruption, heavy exercise, and major stress can temporarily raise cortisol output, so timing the test during a “typical” week can improve interpretability.
What’s included
- Cortisol, Free, 24 Hour Urine
- Cortisol, Free, Urine
- Creatinine, Urine
Frequently Asked Questions
How do I collect a 24-hour urine cortisol test correctly?
You will collect all urine for a full 24 hours. Typically you discard the first morning urine, note the start time, then collect every void after that (including overnight) and include the first urine the next morning at the same time you started. Keep the container as instructed (often refrigerated). Missing even one void can make the result look falsely low, so follow the kit directions closely.
Do I need to fast for a Cortisol Free 24 Hour Urine test?
Fasting is usually not required for a 24-hour urine cortisol collection. However, your clinician may give instructions about alcohol, intense exercise, or medication timing because these can affect cortisol output. If you are unsure, confirm before you start the collection so you do not have to repeat it.
What is the difference between 24-hour urine cortisol and salivary cortisol?
A 24-hour urine test estimates total daily free cortisol output. Salivary cortisol is often collected at specific times (commonly late night) to evaluate whether cortisol is appropriately low when you should be asleep. They answer different questions, and clinicians sometimes use both to confirm or rule out cortisol excess.
Can stress make my 24-hour urine cortisol high?
Yes. Major life stress, acute illness, sleep deprivation, heavy endurance exercise, and uncontrolled blood sugar can raise cortisol output and sometimes cause a temporary elevation. If your result is mildly high and the collection occurred during an unusually stressful or sick period, your clinician may recommend repeating the test under more typical conditions.
Do steroid medications affect urinary free cortisol results?
They can. Prescription steroids (oral, injected, inhaled, nasal, or topical) may suppress your body’s own cortisol production and can also interfere with interpretation depending on the specific medication and assay. Always disclose steroid use and recent steroid injections; your clinician may advise a different test or specific timing.
If my 24-hour urine cortisol is high, what tests usually come next?
Many clinicians confirm with a repeat 24-hour urinary free cortisol and add another first-line test such as late-night salivary cortisol or an overnight dexamethasone suppression test. If cortisol excess is confirmed, additional labs (such as ACTH) help determine whether the source is adrenal or pituitary/ectopic, and imaging is typically considered only after biochemical confirmation.