Testosterone, Bioavailable
Bioavailable testosterone represents the free testosterone plus the portion loosely bound to albumin, together reflecting the testosterone readily accessible to your tissues. It is typically calculated from total testosterone, SHBG, and albumin.
Albumin-bound + free testosterone; calculated from total T, SHBG, and albumin via Vermeulen equation.
This measure can clarify androgen status when binding proteins distort the total testosterone picture. Because albumin-bound testosterone can dissociate and be used by tissues, bioavailable testosterone is sometimes considered a more physiologically meaningful marker than free testosterone alone.
Higher bioavailable testosterone may reflect greater androgen activity, which in people assigned female at birth can relate to conditions like PCOS, or may follow from low binding-protein levels. Interpretation depends on your total testosterone, SHBG, and overall clinical picture.
Reduced bioavailable testosterone can occur with aging, gonadal or pituitary changes, illness, or elevated SHBG, and what it signifies varies considerably by sex and life stage.
Because this value is calculated and strongly sex- and age-dependent, ranges differ between laboratories and methods. Review your result with a clinician who can weigh it against your total testosterone and SHBG.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.