What does the Testosterone, Total, Serum test measure?

Why is Testosterone, Total, Serum measured?

Total testosterone is the first-line androgen assessment marker in both males and females. In males, it provides the primary diagnostic measurement for hypogonadism — the most common androgen deficiency state, with prevalence increasing substantially with age, obesity, and systemic illness. Total testosterone interpretation requires concurrent assessment of LH and FSH to distinguish primary (testicular failure — high LH, high FSH, low testosterone) from secondary (hypothalamic-pituitary failure — low LH, low FSH, low testosterone) hypogonadism, which has different aetiological and therapeutic implications. However, total testosterone alone provides an incomplete picture of androgen bioavailability because SHBG binds testosterone with high affinity and sequester it from tissue uptake — elevated SHBG (from ageing, liver disease, thyroid hormones, or oestrogen) reduces bioavailable testosterone despite normal total testosterone, and reduced SHBG (from insulin resistance, obesity, androgens, or glucocorticoids) increases bioavailable testosterone despite modestly reduced total testosterone. This is why the panel includes free testosterone and SHBG as essential interpretive companions.

Reference ranges

Standard reference

Male (18+): 264–916 ng/dL (9.15–31.76 nmol/L); Female (18+): 10–55 ng/dL (0.35–1.91 nmol/L); Male (paediatric and age-stratified adult values available on request) # REVIEWER FLAG: Confirm LabCorp sex-specific and age-stratified reference ranges for total testosterone. LabCorp's male range has evolved following the Endocrine Society's re-evaluation of testosterone reference ranges; the range above is approximate. Confirm whether LabCorp uses LC-MS/MS (recommended by the Endocrine Society for accuracy, particularly at low female and paediatric concentrations) or immunoassay for total testosterone, as methodology materially affects numerical values and reference ranges, especially at the lower end of the female range.

Functional medicine optimal

Male: 500–900 ng/dL (functional medicine and preventive medicine optimal for metabolic, cardiovascular, cognitive, and reproductive health maintenance — the lower half of the reference range is associated with poorer metabolic outcomes in population studies); Female: 25–50 ng/dL (functional medicine optimal for libido, energy, and musculoskeletal maintenance in premenopausal women). # REVIEWER FLAG: Male testosterone optimal thresholds are the subject of active debate in endocrinology and andrology; the 500 ng/dL lower threshold is more conservative than the current Endocrine Society clinical hypogonadism threshold of approximately 264–300 ng/dL. Reviewer to confirm appropriate framing that distinguishes the functional optimal from the clinical treatment threshold.

Units

ng/dL, nmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.