Testosterone Free (Dialysis), Total (MS) & SHBG
It measures total testosterone by MS, free testosterone by dialysis, and SHBG to clarify hormone status, with Quest-based ordering via Vitals Vault.
This panel bundles multiple biomarker tests in one order—your report explains how results fit together.
This test combines three closely related measurements: total testosterone measured by mass spectrometry (MS), free testosterone measured by equilibrium dialysis, and sex hormone–binding globulin (SHBG). Together, they help clarify how much testosterone you have in circulation and how much is actually available to your tissues.
If you have symptoms that could be hormone-related, a single “total testosterone” number can be misleading when SHBG is unusually high or low. Adding SHBG and a high-quality free testosterone method can explain why you feel “low” even with a total value that looks normal, or why a high total does not always mean excess androgen effect.
Your results are most useful when you interpret them with timing, medications, and your overall health in mind. Testing supports clinician-directed care and follow-up planning, not self-diagnosis.
Do I need a Testosterone Free (Dialysis), Total (MS) & SHBG test?
You may want this combined test if you are trying to make sense of symptoms that can overlap with testosterone imbalance, such as low libido, erectile changes, reduced morning erections, fatigue, depressed mood, loss of muscle, increased body fat, hot flashes, or infertility concerns. In people with ovaries, it can also help evaluate androgen excess patterns that may show up as acne, unwanted hair growth, scalp hair thinning, or irregular cycles.
This specific combination is especially helpful when you suspect binding-protein effects. SHBG acts like a “carrier” that binds testosterone; when SHBG is high, your free (unbound) testosterone can be low even if total testosterone looks acceptable. When SHBG is low, total testosterone can look low while free testosterone is closer to expected.
You may also need this test if you are monitoring hormone therapy or medications that can shift testosterone or SHBG, or if prior results were borderline and you want a more definitive free testosterone method (dialysis) rather than a calculated estimate.
If your symptoms are new, severe, or accompanied by red flags (rapid virilization, testicular pain, severe headaches/vision changes, or unexplained weight loss), use this test as part of a broader clinician-guided evaluation rather than a standalone answer.
Total testosterone by LC-MS/MS and free testosterone by equilibrium dialysis are high-specificity laboratory methods; results should be interpreted in clinical context and are not a standalone diagnosis.
Lab testing
Order Testosterone Free (Dialysis), Total (MS) & SHBG through Vitals Vault when you want a clearer hormone baseline.
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 this combined testosterone assessment for a clear view of total testosterone (MS), free testosterone (dialysis), and SHBG in one blood draw. That matters when you want fewer assumptions and more confidence about whether binding proteins are distorting the story.
After your results post, you can use PocketMD to walk through what “low,” “in range,” or “high” may mean for you, including common follow-up labs to consider and practical retest timing. This is useful if you are comparing options, tracking changes over time, or preparing for a visit with your clinician.
If your results suggest a broader hormone or metabolic pattern, you can reorder the same test for trend clarity or add companion testing through Vitals Vault to map the bigger picture (for example, estradiol, gonadotropins, thyroid markers, or metabolic risk markers).
- Order online and complete your draw through a national lab network
- High-specificity methods: LC-MS/MS total and dialysis free testosterone
- PocketMD support to help you interpret results and plan next steps
Key benefits of Testosterone Free (Dialysis), Total (MS) & SHBG testing
- Clarifies androgen status when symptoms do not match a total testosterone result.
- Separates “how much testosterone you have” (total) from “how much is available” (free).
- Reduces misclassification when SHBG is unusually high or low due to age, thyroid status, liver health, or medications.
- Uses high-specificity methods (LC-MS/MS and dialysis) that can be more reliable at low concentrations.
- Supports safer monitoring if you are on testosterone therapy or medications that affect androgens.
- Helps guide which follow-up labs are most informative (LH/FSH, estradiol, prolactin, DHEA-S, thyroid tests).
- Creates a clean baseline you can trend over time using the same methodology and lab network.
What is Testosterone Free (Dialysis), Total (MS) & SHBG?
This is a combined lab test that reports three related values.
Total testosterone is the overall amount of testosterone in your blood, including testosterone that is bound to proteins and testosterone that is unbound. In this test, total testosterone is measured by liquid chromatography–tandem mass spectrometry (LC-MS/MS), a method designed to improve specificity compared with some immunoassays, especially at lower levels.
Free testosterone is the small fraction of testosterone that is not bound to proteins and is most immediately available to enter tissues. “Equilibrium dialysis” is a reference method for measuring free testosterone because it physically separates free hormone from protein-bound hormone rather than estimating it.
SHBG (sex hormone–binding globulin) is a protein made largely by the liver that binds testosterone (and estradiol) tightly. When SHBG changes, it can shift the balance between total and free testosterone even if your body’s testosterone production has not changed much.
Why SHBG changes matter
If SHBG is high, more testosterone is held tightly in the bloodstream, and your free testosterone can drop. If SHBG is low, free testosterone may be relatively higher for a given total testosterone level. That is why two people with the same total testosterone can have very different free testosterone and symptoms.
Why method matters (MS vs immunoassay; dialysis vs calculated)
Different lab methods can produce meaningfully different numbers, particularly at the low end of the range and in people with lower baseline testosterone. LC-MS/MS for total testosterone and equilibrium dialysis for free testosterone are commonly used when accuracy is a priority or when prior results were confusing.
What do my Testosterone Free (Dialysis), Total (MS) & SHBG results mean?
Low results (total and/or free testosterone)
Low total testosterone, low free testosterone, or both can align with hypogonadism patterns, but the “why” matters. In some cases, low values reflect reduced testicular/ovarian production or reduced pituitary signaling (often evaluated with LH and FSH). In other cases, total may be low while free is less affected because SHBG is low, which can happen with insulin resistance, obesity, or certain medications. A single low result is usually confirmed with a repeat morning sample (often on a different day) before treatment decisions are made.
In-range (optimal) results
When total testosterone, free testosterone, and SHBG are all in a typical range for your age and sex, it suggests your circulating androgen status is broadly consistent with population norms. If you still have symptoms, the next step is often to look for other explanations or contributing factors, such as sleep quality, thyroid function, iron status, depression/anxiety, medication effects, or cardiometabolic health. “In range” does not always mean “ideal for you,” but it makes a primary testosterone deficiency less likely. Trending results over time can be more informative than focusing on a single number.
High results (total and/or free testosterone)
High testosterone can occur from exogenous testosterone use, certain supplements or medications, or less commonly from endocrine conditions that increase androgen production. If total testosterone is high but free testosterone is not as elevated, SHBG may be high and binding more hormone. If free testosterone is clearly high, clinicians often consider potential sources of androgen excess and may pair testing with estradiol, DHEA-S, and gonadotropins depending on your anatomy and symptoms. Persistently high levels can matter because they may increase risks such as acne, hair loss, mood changes, elevated hematocrit on therapy, or menstrual disruption in people with ovaries.
Factors that influence testosterone and SHBG
Timing is a major factor: testosterone is often highest in the morning, and shift work or poor sleep can blunt that pattern. Medications can change results, including testosterone therapy, anabolic steroids, opioids, glucocorticoids, some anticonvulsants, and estrogen-containing therapies; biotin can interfere with some immunoassays (less so with MS/dialysis methods, but it is still worth disclosing). Thyroid status, liver health, nutritional status, and body composition can shift SHBG, which then changes free testosterone even if total testosterone is stable. Acute illness, heavy training blocks, and calorie restriction can also temporarily affect hormone levels, so retesting when you are back to baseline can prevent overinterpretation.
What’s included
- Sex Hormone Binding Globulin
- Testosterone, Free
- Testosterone, Total, Ms
Frequently Asked Questions
What is the difference between free testosterone and total testosterone?
Total testosterone is the overall amount in your blood, including protein-bound and unbound hormone. Free testosterone is the unbound portion that is most readily available to tissues. SHBG strongly affects how much of your total ends up in the free fraction, which is why measuring SHBG alongside free and total can clarify confusing results.
Why is free testosterone measured by dialysis?
Equilibrium dialysis physically separates free hormone from protein-bound hormone, which can make it more reliable than calculated free testosterone when SHBG or albumin levels are unusual. It is often used when accuracy is important or when prior testing did not match symptoms.
Do I need to fast for this test?
Fasting is not always required for testosterone and SHBG, but many people schedule morning labs and may fast if they are also checking glucose, insulin, or lipids. Follow the collection instructions you receive, and try to keep your routine consistent if you plan to trend results.
When is the best time of day to test testosterone?
For many people, testosterone peaks in the morning, so clinicians often prefer a morning draw (commonly before 10 a.m.), especially when evaluating possible low testosterone. If you do shift work or have irregular sleep, the best timing may be “soon after your longest sleep period,” and consistency across repeat tests becomes even more important.
How often should I retest if my result is low or borderline?
A common approach is to repeat testing on a different morning to confirm a low or borderline value, ideally when you are not acutely ill and your sleep has been typical. If you are monitoring therapy, retest timing depends on the medication and dosing schedule, so it is best set with your prescribing clinician.
Can SHBG be high or low even if I feel fine?
Yes. SHBG can shift with age, thyroid status, liver function, estrogen exposure, and body composition, and you may not feel a direct symptom from SHBG itself. The reason it matters is that it changes how much free testosterone you have for a given total testosterone level.
What other labs are commonly checked with this test?
Common companions include LH and FSH (to assess signaling from the pituitary), estradiol (especially if symptoms suggest estrogen imbalance or if you are on testosterone therapy), prolactin (when libido or gonadotropins are abnormal), and DHEA-S (for broader androgen evaluation). Depending on your situation, thyroid testing, metabolic markers, and a complete blood count may also be relevant.