Free + Total Testosterone Test
The Free + Total Testosterone test measures total testosterone together with the free, unbound fraction to assess androgen status. Reporting both matters because total testosterone can mislead when sex hormone-binding globulin is abnormal, while the free fraction reflects the hormone accessible to tissues.
2
Biomarkers
Blood (serum)
Sample
2–4 business days
Turnaround
No
Fasting
What is the Free & Total Testosterone test?
The Free + Total Testosterone Test measures total testosterone together with the free, unbound fraction, giving a fuller picture of androgen status than the total value alone. Reporting both matters because total testosterone can misrepresent the biologically available hormone whenever sex hormone-binding globulin is abnormal, and the free fraction reflects the testosterone actually accessible to tissues. In the diagnostic landscape, total testosterone is the recommended first-line measure for androgen assessment, performed on a morning sample and confirmed when low. Adding free testosterone resolves the ambiguity that arises when SHBG is altered by obesity, ageing, thyroid or hepatic disease, or hormonal therapy, situations in which the total value alone may mislead. This two-fraction panel is appropriate when a borderline total testosterone or a likely binding-protein abnormality means the free fraction is needed, while a standalone total suffices for routine first-line screening. The reliability of the free result depends on the method used, with equilibrium dialysis or calculation preferred over direct analogue immunoassay.
What does the Free & Total Testosterone test measure?
Testosterone is the principal androgen, produced mainly by the testicular Leydig cells in men and in smaller amounts by the ovaries and adrenal cortex in women, under luteinising hormone and hypothalamic-pituitary-gonadal control. In serum roughly half is bound tightly to sex hormone-binding globulin (SHBG), most of the rest loosely to albumin, with a small free fraction. Total testosterone is the sum of all fractions and shows a morning-peak diurnal rhythm.
Total testosterone is the first-line measure of androgen status but can mislead when SHBG is abnormal. Pairing it with free testosterone clarifies the biologically available hormone, which is particularly useful when total values are borderline or binding-protein abnormalities are likely.
Free testosterone is the small unbound fraction not attached to SHBG or albumin and is considered the immediately bioavailable, biologically active portion. It is best measured by equilibrium dialysis or calculated from total testosterone, SHBG, and albumin; direct analogue immunoassays for free testosterone are regarded as unreliable.
Free testosterone clarifies androgen status when total testosterone is equivocal or SHBG is altered by obesity, thyroid disease, hepatic disease, ageing, or hormonal therapy. It is particularly useful in diagnosing hypogonadism where total testosterone sits near the lower reference limit, and in assessing androgen excess in women.
Why is the Free & Total Testosterone test ordered?
- Investigation of suspected male hypogonadism, particularly where total testosterone sits near the lower reference limit and SHBG status is uncertain
- Assessment of androgen status in men with conditions that alter SHBG — obesity, type 2 diabetes, thyroid disease, or hepatic disease
- Evaluation of androgen excess in women — hirsutism, acne, or suspected polycystic ovary syndrome — where the free fraction adds information
- Monitoring of testosterone replacement therapy where free and total values are tracked
- Investigation of erectile dysfunction, reduced libido, or fatigue where androgen deficiency is in the differential
- Assessment in older men where age-related SHBG rise can make total testosterone misleading
- Clarification of a borderline or discordant total testosterone where the free fraction is needed to characterise androgen availability
Sample collection and turnaround
Sample type
Blood (serum)
Fasting required
No
Collection method
Venipuncture at patient service centre
Turnaround
2–4 business days
Collection notes
Draw in the morning, ideally before 10:00, to account for diurnal variation when assessing hypogonadism. Document testosterone or anabolic steroid use, opioids, glucocorticoids, and high-dose biotin. Defer testing during acute illness where possible, and confirm a low result on a separate morning sample.
Specimen requirements
Minimum 1.0 mL serum. Separate serum from cells within 2 hours of collection.
What can affect Free & Total Testosterone results?
Testosterone peaks in the morning and declines through the day, so samples for hypogonadism assessment should be drawn in the morning, ideally before 10:00, for valid interpretation.
Changes in SHBG shift the bound-to-free balance, so total testosterone can mislead while the free fraction remains the reliable guide. This is the core rationale for measuring both.
Results depend on whether free testosterone is measured by equilibrium dialysis or calculated, and direct analogue immunoassays are unreliable; method affects both the value and its interpretation. # REVIEWER FLAG: Confirm LabCorp method.
Significant illness suppresses the hypothalamic-pituitary-gonadal axis, transiently lowering testosterone; assessment should be deferred until recovery where possible.
Androgen supplementation raises measured testosterone and suppresses endogenous production; type, dose, and timing must be documented relative to collection.
Chronic opioids and glucocorticoids suppress gonadotrophin drive and lower testosterone, while high-dose biotin can interfere with some immunoassay steps used in measurement or calculation. # REVIEWER FLAG: Confirm assay susceptibility.
What do Free & Total Testosterone results mean?
Elevated
Elevated testosterone in men may reflect exogenous androgen use or, rarely, an androgen-secreting tumour; in women it raises concern for polycystic ovary syndrome or adrenal or ovarian androgen excess. A low SHBG can yield a high free fraction relative to total, clarifying androgen excess the total value understates.
Normal
Values within age- and sex-specific ranges for both fractions indicate adequate androgen status. A normal total with a discordant free fraction points to an SHBG effect and should be interpreted using the free result.
Reduced
Low testosterone, confirmed on a morning sample, supports hypogonadism, and a low free fraction is particularly informative when the total is borderline or SHBG is altered. A high SHBG can produce a low free testosterone despite a normal-appearing total; LH and FSH distinguish primary from secondary causes.
Note: Total testosterone is unreliable when SHBG is abnormal, which is precisely when the free fraction guides interpretation. The reliability of the free result depends on method, with equilibrium dialysis or calculation preferred over direct immunoassay. Morning sampling and confirmation of low results are important, and method differences mean free testosterone reference ranges are not interchangeable between laboratories.
Frequently asked questions
Total testosterone is the sum of all circulating fractions, while free testosterone is the small unbound, biologically active portion. The free fraction is added when sex hormone-binding globulin is abnormal and the total value may mislead.
How to access the Free & Total Testosterone test
The Free & Total Testosterone reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.
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Published: June 3, 2026
Last reviewed: June 3, 2026
- Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. (2018)
- Rosner W, et al. Position statement: Utility, limitations, and pitfalls in measuring testosterone. J Clin Endocrinol Metab. (2007)
- Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab. (1999)
- Travison TG, et al. Harmonized Reference Ranges for Circulating Testosterone Levels in Men. J Clin Endocrinol Metab. (2017)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.
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