Testosterone Free, Bioavailable & Total (MS) Biomarker Testing
It measures total, free, and bioavailable testosterone to clarify hormone status; order through Vitals Vault and test at a Quest location.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
This test gives you a more complete view of testosterone than “total testosterone” alone. It reports total testosterone measured by mass spectrometry (LC-MS/MS), and it also reports the portion that is free and the portion that is bioavailable.
That distinction matters because most testosterone in your blood is bound to proteins, especially sex hormone–binding globulin (SHBG). If SHBG is unusually high or low, your total testosterone can look “fine” while the amount your tissues can actually use is not.
Your result is most useful when you interpret it alongside your symptoms, medications, and timing of the blood draw. It can support clinician-directed care, but it is not a standalone diagnosis.
Do I need a Testosterone Free Bioavailable And Total MS test?
You may want this test if you are trying to make sense of symptoms that can overlap with many other conditions, such as lower libido, fewer morning erections, fatigue, reduced exercise performance, depressed mood, or difficulty gaining muscle despite training. In people with ovaries, it can also help evaluate signs of androgen excess such as acne, scalp hair thinning, or increased facial/body hair.
This specific “free + bioavailable + total” approach is especially helpful when total testosterone does not match how you feel, or when you have reasons for SHBG to be abnormal. Common scenarios include obesity or insulin resistance (often lower SHBG), thyroid disease, liver disease, aging, pregnancy, and use of estrogen-containing medications (often higher SHBG).
You may also need it if you are monitoring treatment that can change testosterone availability, such as testosterone therapy, selective estrogen receptor modulators, aromatase inhibitors, or changes in estrogen exposure. In those cases, trending the same method over time is usually more informative than a single number.
If you are deciding what to do next, your clinician will often pair these results with other hormones (like LH, FSH, estradiol, prolactin, and thyroid tests) to identify whether the issue is testicular/ovarian, pituitary, medication-related, or driven by binding proteins.
This is a laboratory blood test typically performed in a CLIA-certified lab; results should be interpreted in clinical context and are not diagnostic on their own.
Lab testing
Order Testosterone Free, Bioavailable & Total (MS) through Vitals Vault and schedule your draw at Quest.
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 Testosterone Free Bioavailable And Total MS directly, then complete your blood draw at a nearby Quest location. This is useful when you want a high-quality baseline, you are comparing options, or you need a consistent method for follow-up testing.
After your results post, you can use PocketMD to walk through what “free,” “bioavailable,” and “total” mean for your situation, what patterns are worth rechecking, and which companion labs can reduce guesswork (for example, SHBG, albumin, LH/FSH, estradiol, or prolactin).
If you are retesting, PocketMD can also help you plan timing so your trend is meaningful—such as drawing in the morning when appropriate, keeping medication timing consistent, and repeating an abnormal result before making big changes.
- Order online and draw at a Quest location
- PocketMD guidance for next-step questions to discuss with your clinician
- Designed for trending: consistent, repeatable lab monitoring
Key benefits of Testosterone Free Bioavailable And Total MS testing
- Clarifies testosterone status when total testosterone alone does not match your symptoms.
- Separates protein-bound from usable testosterone by reporting free and bioavailable fractions.
- Helps identify SHBG-driven patterns that can mask low or high androgen availability.
- Supports evaluation of low libido, fatigue, mood changes, and performance concerns in context.
- Improves assessment of androgen excess patterns when testosterone is near the upper end of range.
- Creates a consistent baseline for monitoring therapy or medication changes that affect hormones.
- Makes follow-up planning easier when paired with PocketMD and targeted companion labs.
What is Testosterone Free Bioavailable And Total MS?
Testosterone is an androgen hormone that influences sexual function, fertility, muscle and bone maintenance, red blood cell production, and aspects of mood and energy. In blood, testosterone exists in three main forms: tightly bound to SHBG, loosely bound to albumin, and unbound (free).
Total testosterone is the sum of all forms. Free testosterone is the small fraction not bound to proteins. Bioavailable testosterone generally refers to free testosterone plus the albumin-bound portion, because albumin binding is weak and testosterone can dissociate and become available to tissues.
The “MS” in the name refers to mass spectrometry (often LC-MS/MS), a measurement method widely used for steroid hormones. Method matters because immunoassays can be less reliable at lower concentrations (a common issue in women and in men with low testosterone).
Why SHBG changes the story
SHBG acts like a carrier that holds onto testosterone. When SHBG is high, more testosterone is bound and less may be free/bioavailable even if total looks acceptable. When SHBG is low, total testosterone can look low while free/bioavailable is normal or high. That is why a “free + bioavailable + total” report can be more actionable than a single total value.
Why timing and consistency matter
Testosterone varies across the day and can be affected by sleep, illness, calorie restriction, heavy training, and medications. If you are trending results, try to keep the draw time and conditions similar each time, and discuss medication timing with your clinician so you are comparing like with like.
What do my Testosterone Free Bioavailable And Total MS results mean?
Low testosterone (total, free, or bioavailable)
Low free or bioavailable testosterone can help explain symptoms like reduced libido, fewer spontaneous erections, low energy, or decreased strength—especially when the pattern repeats on a second morning draw. If total testosterone is low but free/bioavailable is not, low SHBG is often part of the explanation, and the next step is usually to look for drivers such as weight changes, insulin resistance, certain medications, or systemic illness. If both total and free/bioavailable are low, your clinician may evaluate whether the cause is testicular/ovarian versus pituitary by checking LH and FSH, and may add prolactin and thyroid testing depending on the picture.
In-range (optimal) testosterone pattern
An in-range total testosterone with in-range free and bioavailable fractions generally suggests that binding proteins and hormone production are in balance. If you still have symptoms, it does not mean “nothing is wrong,” but it makes testosterone a less likely primary driver. In that situation, clinicians often look at sleep, mood, thyroid function, iron status, medications, and other hormones (such as estradiol or cortisol patterns) depending on your history.
High testosterone (total, free, or bioavailable)
High free or bioavailable testosterone can occur with testosterone therapy, anabolic steroid exposure, or conditions that increase androgen production. In people with ovaries, elevated testosterone may support evaluation for androgen excess patterns, especially when paired with symptoms like acne or hirsutism and with related tests such as DHEA-S and 17-hydroxyprogesterone. If total is high but free is not, high SHBG (for example from estrogen exposure or hyperthyroidism) can raise total while keeping free closer to normal.
Factors that influence testosterone results
Time of day, recent sleep, acute illness, heavy endurance training, and calorie deficit can all lower testosterone transiently. SHBG shifts the relationship between total and free/bioavailable and is influenced by age, thyroid status, liver function, estrogen exposure, and metabolic health. Medications and hormones—including testosterone formulations, estrogen-containing contraceptives, anti-androgens, opioids, and glucocorticoids—can change results and should be reviewed before interpreting a single value. Because reference ranges and units vary by lab, your “low” or “high” should be judged against the range on your report and confirmed with repeat testing when decisions are significant.
What’s included
- Albumin
- Sex Hormone Binding Globulin
- Testosterone,Bioavailable
- Testosterone, Free
- Testosterone, Total, Ms
Frequently Asked Questions
What is the difference between total, free, and bioavailable testosterone?
Total testosterone is everything in your blood (bound + unbound). Free testosterone is the unbound fraction. Bioavailable testosterone is free testosterone plus the portion loosely bound to albumin, which can more readily enter tissues.
Why does SHBG matter for interpreting testosterone?
SHBG binds testosterone tightly. High SHBG can make total testosterone look normal or high while free/bioavailable is lower. Low SHBG can make total look low while free/bioavailable is normal or high, which changes what “low testosterone” means in practice.
Is LC-MS/MS (mass spectrometry) better than an immunoassay for testosterone?
Mass spectrometry is generally preferred for accuracy and specificity, especially at lower testosterone concentrations. That can be important for women, for men with suspected low testosterone, and for consistent monitoring over time.
When should I get my testosterone drawn?
Many clinicians prefer a morning draw (often before 10 a.m.) for men because testosterone can be higher earlier in the day. If you are monitoring therapy, the best timing depends on the formulation and dosing schedule, so keep timing consistent and follow your clinician’s guidance.
Do I need to fast for this test?
Fasting is not always required for testosterone itself, but you may be ordering companion labs (like lipids or glucose/insulin markers) that do require fasting. If you are unsure, follow the instructions on your lab order and aim for consistency between repeat tests.
How often should I retest if my result is low or borderline?
A common approach is to repeat an abnormal or borderline result on a separate day under similar conditions, because sleep loss, illness, and stress can temporarily lower testosterone. Your clinician may recommend retesting in a few weeks to a few months depending on symptoms, how abnormal the value is, and whether you are making changes (weight, medications, or therapy).
What other labs are commonly checked with testosterone?
Common companions include LH and FSH (to assess pituitary signaling), estradiol, prolactin, thyroid tests, and sometimes DHEA-S, 17-hydroxyprogesterone, or a metabolic panel depending on whether the concern is low testosterone, androgen excess, or treatment monitoring.