Testosterone Free (Dialysis) and Total (MS) Biomarker Testing
It measures total testosterone by mass spectrometry and free testosterone by dialysis to clarify symptoms and treatment decisions, with easy ordering through Vitals Vault/Quest.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
This test combines two high-specificity measurements: total testosterone measured by mass spectrometry (MS/LC-MS/MS) and free testosterone measured by equilibrium dialysis. Together, they help you understand not just how much testosterone is in your blood, but how much is actually available to your tissues.
It can be especially useful when symptoms and “total testosterone” do not match, or when binding proteins (like SHBG) are likely to be abnormal. You can use the result to guide a clinician conversation about next steps, not to diagnose yourself.
Do I need a Testosterone Free (Dialysis) and Total (MS) test?
You may want this test if you have symptoms that could fit low or high androgen levels, but the picture is not straightforward. For many people, that looks like lower libido, erectile changes, fatigue, depressed mood, reduced exercise recovery, or loss of muscle mass. In others, it looks like acne, scalp hair thinning, increased body hair, irregular periods, or signs of androgen excess.
This combined method is most helpful when total testosterone alone can be misleading. That can happen if your sex hormone–binding globulin (SHBG) is high or low, if you are older, if you have obesity or insulin resistance, if you are pregnant, or if you use certain medications (for example, estrogen-containing therapies, some anticonvulsants, or glucocorticoids). In these settings, free testosterone by dialysis can better reflect the biologically active fraction.
You may also need it to monitor therapy. If you use testosterone replacement therapy (TRT), gender-affirming hormone therapy, or medications that affect androgens, measuring both total (by MS) and free (by dialysis) can help your clinician adjust dose and timing while reducing the chance of over- or under-treatment.
Testing supports clinician-directed care. Your result is one data point that should be interpreted alongside symptoms, exam findings, and related labs.
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 Testosterone Free (Dialysis) and Total (MS) through Vitals Vault and schedule your draw.
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 confirm that a prior testosterone result is accurate, Vitals Vault lets you order Testosterone Free (Dialysis) and Total (MS) without a referral and complete your draw through the Quest network.
After your results post, you can use PocketMD to ask practical questions like whether your pattern fits low testosterone, whether SHBG might be distorting total testosterone, and what follow-up labs are commonly paired with this test. That helps you show up to your next clinician visit with clearer questions and a plan.
If you are monitoring treatment, you can also use Vitals Vault to retest at a consistent time point (for example, same time of day and same point in your dosing cycle) so trends are easier to interpret.
- Order online and draw at a Quest location
- PocketMD helps you interpret results in context
- Easy retesting to track trends over time
Key benefits of Testosterone Free (Dialysis) and Total (MS) testing
- Clarifies symptoms when total testosterone and how you feel do not line up.
- Uses LC-MS/MS for total testosterone, which is more specific than many immunoassays at low levels.
- Measures free testosterone by equilibrium dialysis, a reference method when SHBG is abnormal.
- Helps distinguish low production from altered binding when paired with SHBG and albumin.
- Supports safer dose adjustments when you are on TRT or other androgen-affecting therapies.
- Improves evaluation of androgen excess patterns when combined with DHEA-S and androstenedione.
- Creates a reliable baseline you can trend over time with consistent collection timing.
What is Testosterone Free (Dialysis) and Total (MS)?
Testosterone is a steroid hormone involved in sexual function, fertility, red blood cell production, mood, energy, and body composition. In blood, most testosterone is bound to proteins—mainly SHBG and albumin—and only a small fraction circulates as “free” testosterone.
Total testosterone is the sum of free plus protein-bound testosterone. Free testosterone is the unbound portion that can more readily enter tissues and activate androgen receptors. When SHBG is unusually high or low, total testosterone can look “normal” while free testosterone is meaningfully low (or the reverse).
This test measures:
• Total testosterone using mass spectrometry (often reported as LC-MS/MS), which improves accuracy and reduces cross-reactivity compared with many older methods. • Free testosterone using equilibrium dialysis, which physically separates free hormone from bound hormone and is often used as a reference approach.
Because the two measurements answer different questions, ordering them together can reduce uncertainty—especially when you are near a decision point (for example, whether symptoms are likely androgen-related, or whether a therapy dose is too high).
Why SHBG matters
SHBG is a binding protein that controls how much testosterone is carried in a tightly bound form. Higher SHBG tends to lower free testosterone for a given total testosterone, while lower SHBG can raise free testosterone even when total is not high. Common reasons SHBG shifts include aging, thyroid status, liver disease, obesity/insulin resistance, pregnancy, and estrogen exposure.
Why method matters (MS and dialysis)
At lower testosterone concentrations—common in women and in some men with hypogonadism—some immunoassays can be less reliable. LC-MS/MS improves specificity for total testosterone, and equilibrium dialysis is used to directly measure the free fraction rather than estimating it from formulas that can be thrown off by unusual binding conditions.
What do my Testosterone Free (Dialysis) and Total (MS) results mean?
Low testosterone (total and/or free)
If your total testosterone by MS is low, your body may be producing less testosterone than expected, which can relate to testicular/ovarian function, pituitary signaling, medications, or systemic illness. If total is borderline but free testosterone by dialysis is clearly low, abnormal binding (often higher SHBG) may be limiting the amount available to tissues. Your clinician will often pair this with LH and FSH (and sometimes prolactin) to help localize the cause, and may repeat the test in the morning (and on a second day) to confirm a persistent pattern.
In-range results (with symptoms or without)
If both total and free testosterone are in range for your age and sex, that generally argues against testosterone being the main driver of your symptoms. However, “in range” does not always mean “optimal for you,” especially if the result was drawn late in the day, during acute illness, or at an inconsistent point in a dosing cycle. If symptoms persist, it is common to look at related markers such as SHBG, estradiol, thyroid function, iron status, sleep quality, and metabolic health.
High testosterone (total and/or free)
High total testosterone by MS can occur with exogenous testosterone use, certain ovarian/testicular conditions, or less commonly adrenal sources. If free testosterone by dialysis is high, it suggests more hormone is biologically available, which can increase the chance of androgen-related side effects such as acne, hair changes, mood irritability, or changes in hematocrit on therapy. When results are high, follow-up often focuses on confirming timing (especially if you use injections or gels), reviewing medications/supplements, and checking companion labs like estradiol, hematocrit/hemoglobin, and PSA (for appropriate populations).
Factors that influence testosterone results
Timing matters: testosterone follows a daily rhythm in many men, so morning collection is commonly recommended for diagnostic evaluation, and consistency is key for monitoring. SHBG shifts can change free testosterone even when total looks stable, and estrogen exposure, thyroid status, liver disease, and insulin resistance are frequent contributors. Acute illness, poor sleep, heavy training, calorie restriction, and alcohol can temporarily lower testosterone. Biotin, some steroids, and androgenic medications can also affect results or interpretation, so bring a full medication and supplement list to your clinician.
What’s included
- Testosterone, Free
- Testosterone, Total, Ms
Frequently Asked Questions
What is the difference between free testosterone (dialysis) and calculated free testosterone?
Free testosterone by equilibrium dialysis is a direct measurement of the unbound fraction after separating it from protein-bound testosterone. Calculated free testosterone estimates the free fraction using total testosterone plus binding assumptions (often SHBG and albumin). Calculations can be useful, but they can be less reliable when SHBG is unusually high or low or when binding conditions are atypical.
Is LC-MS/MS better than a standard testosterone test?
LC-MS/MS (mass spectrometry) is generally more specific and can be more accurate at lower testosterone concentrations because it reduces cross-reactivity seen with some immunoassays. That is particularly relevant for women, for people with very low testosterone, and when you are trying to confirm a borderline result.
When should I get my testosterone drawn for the most accurate result?
For diagnostic evaluation in many men, a morning draw is commonly recommended because levels can be higher earlier in the day. For therapy monitoring, the “best” time depends on your dosing method (injection, gel, pellets), but the most important rule is consistency—same time of day and same point in your dosing cycle—so trends are interpretable.
Do I need to fast for this test?
Fasting is not usually required for testosterone testing. If you are getting other labs at the same visit (like lipids or glucose/insulin), fasting instructions may come from those tests instead. Avoiding heavy alcohol intake and extreme exercise right before the draw can help reduce avoidable variability.
What other labs are commonly ordered with free and total testosterone?
Common companion tests include SHBG and albumin (to understand binding), LH and FSH (to assess pituitary signaling), prolactin (when low testosterone is unexplained), estradiol (especially on therapy), and sometimes DHEA-S or androstenedione if androgen excess is a concern. Your clinician may also consider CBC (hematocrit) and PSA for appropriate populations when monitoring testosterone therapy.
How often should I retest testosterone?
If you are confirming a possible low result, clinicians often repeat testing on a separate morning to confirm persistence. If you are starting or adjusting therapy, retesting is commonly done after levels have had time to stabilize and at a consistent timing relative to dosing. Your exact interval depends on symptoms, treatment changes, and any safety monitoring labs your clinician is following.