Cortisol Free and Total (LC/MS) Biomarker Testing
It measures both free and total cortisol in blood to clarify stress-hormone status and binding effects, with convenient ordering through Vitals Vault labs.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
Cortisol is your body’s main “stress hormone,” but it is also a daily rhythm hormone. It helps regulate blood sugar, blood pressure, immune activity, and how alert you feel across the day.
A Cortisol Free and Total (LC/MS) test measures two related values at the same time: total cortisol (most of what circulates in blood) and free cortisol (the unbound portion that is biologically active). Seeing both can help explain why symptoms and a single cortisol number do not always match.
Because cortisol changes by time of day and can be affected by medications and binding proteins, this test is most useful when it is ordered with a clear plan for timing and follow-up with your clinician.
Do I need a Cortisol Free and Total (LC/MS) test?
You may consider this test if you and your clinician are trying to make sense of symptoms that could relate to cortisol imbalance, such as persistent fatigue, sleep disruption, unexplained weight change, new muscle weakness, frequent infections, easy bruising, or feeling “wired but tired.” It can also be helpful when you have low blood pressure or dizziness on standing, or when you have high blood pressure and blood sugar changes that do not fit your usual pattern.
This specific version—free and total measured by LC/MS (liquid chromatography–mass spectrometry)—is often chosen when accuracy matters and when binding effects could distort interpretation. For example, estrogen-containing birth control, pregnancy, and some liver conditions can raise cortisol-binding globulin (CBG), which can increase total cortisol even if free cortisol is normal.
You may also need cortisol testing if you are being evaluated for adrenal insufficiency (low cortisol) or cortisol excess (such as Cushing syndrome), or if you are monitoring steroid therapy. If your symptoms are urgent or severe, testing should support clinician-directed care rather than self-diagnosis.
This is a laboratory-developed test performed in a CLIA-certified lab; results are for education and clinical decision support and are not a standalone diagnosis.
Lab testing
Order Cortisol Free and Total (LC/MS) through Vitals Vault and test at a local lab.
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
Vitals Vault lets you order Cortisol Free and Total (LC/MS) testing without a referral and complete your blood draw at a convenient lab location. You get a clear report you can share with your clinician, with the same practical goal: turning a single number into a next step.
Because cortisol is time-sensitive, ordering through Vitals Vault can make it easier to plan the right collection window (often morning) and to repeat the test when your clinician wants confirmation. Trending matters with cortisol, especially when symptoms fluctuate or when medication changes are involved.
If you want help interpreting your result in context—your symptoms, timing, medications, and related labs—PocketMD can walk you through what to ask next and what follow-up testing is commonly used to confirm or rule out specific patterns.
- Order online and test at a nearby lab location
- PocketMD guidance for next-step questions and retest planning
- Easy re-ordering when your clinician wants confirmation or trends
Key benefits of Cortisol Free and Total (LC/MS) testing
- Separates free (active) cortisol from total cortisol so binding effects are easier to spot.
- Uses LC/MS methodology, which can improve analytical specificity compared with some immunoassays.
- Helps evaluate symptoms that may relate to low cortisol, high cortisol, or disrupted daily rhythm.
- Supports clinician workups for adrenal insufficiency or cortisol excess when paired with confirmatory tests.
- Provides a clearer baseline before and after medication changes that affect cortisol or binding proteins.
- Helps explain “normal total cortisol” when free cortisol is abnormal (or the reverse).
- Makes it easier to plan retesting at the same time of day to track meaningful change over time.
What is Cortisol Free and Total (LC/MS)?
Cortisol is a steroid hormone made by your adrenal glands. Your brain regulates cortisol through the hypothalamic–pituitary–adrenal (HPA) axis, and your levels normally follow a daily pattern: higher in the morning and lower at night.
In blood, most cortisol is bound to proteins—mainly cortisol-binding globulin (CBG) and albumin. Bound cortisol acts like “stored” hormone that is carried through the bloodstream. Free cortisol is the small unbound fraction that can enter tissues and activate cortisol receptors.
A “total cortisol” result reflects both bound and free cortisol together. A “free cortisol” result aims to reflect the biologically active portion. Measuring both with LC/MS can be useful when you suspect that changes in binding proteins (not just cortisol production) are influencing your total cortisol number.
Why time of day matters
Cortisol is not a static biomarker. A sample drawn in the early morning can look very different from one drawn in the afternoon, even in the same person. When you compare results over time, matching the collection time is one of the most important ways to make the trend meaningful.
How this differs from saliva or urine cortisol
Blood cortisol reflects what is circulating at the moment of the draw. Salivary cortisol is often used for late-night testing, and 24-hour urine free cortisol is used to estimate daily cortisol production. These tests answer different questions, so your clinician may choose one based on the pattern they are evaluating.
What do my Cortisol Free and Total (LC/MS) results mean?
Low cortisol (free and/or total)
Low cortisol can fit with adrenal insufficiency, especially if you also have symptoms such as severe fatigue, weight loss, nausea, low blood pressure, or salt craving. However, a single low value is not enough to diagnose the cause because timing, acute illness, and recent steroid exposure can suppress cortisol. If your result is low, your clinician may confirm with an ACTH (cosyntropin) stimulation test and may also check ACTH, electrolytes, and glucose to clarify whether the issue is adrenal or pituitary in origin.
In-range cortisol with an expected free-to-total pattern
An in-range result that matches the expected time of day usually suggests your circulating cortisol is appropriate for that moment. If your symptoms persist, the next step is often to look for patterns rather than a single snapshot, such as repeating at the same time, checking related hormones, or evaluating sleep, inflammation, and medication effects. “Normal” does not rule out all cortisol-related conditions, but it makes severe deficiency or marked excess less likely when the sample timing is appropriate.
High cortisol (free and/or total)
High cortisol can occur with physiologic stress (pain, poor sleep, intense exercise, acute illness), but persistent elevation raises the question of cortisol excess. If total cortisol is high while free cortisol is not, increased binding proteins (such as higher CBG from estrogen therapy or pregnancy) may be contributing. If free cortisol is high, your clinician may consider confirmatory testing based on your situation, such as late-night salivary cortisol, 24-hour urine free cortisol, or a dexamethasone suppression test.
Factors that influence cortisol results
Collection time is a major driver of your result, so always compare morning-to-morning or afternoon-to-afternoon. Medications matter: oral, inhaled, injected, or topical glucocorticoids can suppress your own cortisol production, and estrogen-containing therapies can raise CBG and total cortisol. Pregnancy, liver disease, kidney disease, thyroid status, and significant changes in albumin can shift the relationship between free and total cortisol. Even short-term factors like poor sleep, heavy training, alcohol use, and acute infection can temporarily raise cortisol.
What’s included
- Cortisol,Free,Lc/Ms,S
- Cortisol, Total, Lc/Ms
Frequently Asked Questions
What is the difference between free cortisol and total cortisol?
Total cortisol includes both protein-bound cortisol and free cortisol together. Free cortisol is the unbound fraction that is more directly biologically active. Measuring both can help when binding proteins (like CBG) are altered, which can make total cortisol look higher or lower than your active cortisol exposure.
Do I need to fast for a cortisol blood test?
Fasting is not always required for cortisol itself, but your clinician or the lab may prefer a morning draw and may combine cortisol with other tests that do require fasting. The most important preparation detail is timing and avoiding unusual stressors (like a hard workout) right before the draw when possible.
What time should cortisol be tested?
Cortisol is commonly tested in the morning because levels are usually highest then, and many reference intervals are built around morning collection. If your clinician is evaluating a specific pattern (such as loss of nighttime suppression), they may choose a different time or a different specimen type such as late-night saliva.
Can birth control or estrogen therapy affect cortisol results?
Yes. Estrogen can increase cortisol-binding globulin (CBG), which can raise total cortisol even when free cortisol is normal. That is one reason a free-and-total LC/MS approach can be useful when you are on estrogen-containing contraception or hormone therapy.
Is a high cortisol result the same as Cushing syndrome?
No. Cortisol can be temporarily high due to stress, illness, pain, poor sleep, or certain medications. Diagnosing Cushing syndrome typically requires confirmatory testing (often more than one type) and clinical correlation, not a single blood value.
Is a low cortisol result the same as Addison’s disease?
Not necessarily. Low cortisol can occur for multiple reasons, including recent or current steroid medication use, pituitary signaling problems, or acute illness effects. Addison’s disease is one cause of primary adrenal insufficiency, and diagnosis usually involves additional labs and often an ACTH stimulation test.
When should I retest cortisol?
Retesting depends on why you tested in the first place. If the result is borderline or unexpected, clinicians often repeat the test at the same time of day under more typical conditions, or they move to a confirmatory test that better answers the clinical question. PocketMD can help you prepare questions about timing, medications, and the most appropriate follow-up test.