Bioavailable testosterone optimal range and reference range

Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026

Sera's bands for Bioavailable testosterone, which differ for men and women:

  • Male: Optimal 40 – 250 ng/dL (1.39 – 8.68 nmol/L); out of range below 40 or above 250 ng/dL.
  • Female: Optimal 0 – 9.5 ng/dL (0 – 0.33 nmol/L); out of range below 0 or above 9.5 ng/dL.

Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.

All units

UnitApplies toOptimalSufficientOut of range
ng/dLMale40 – 250—below 40 or above 250
ng/dLFemale0 – 9.5—below 0 or above 9.5
nmol/LMale1.39 – 8.68—below 1.39 or above 8.68
nmol/LFemale0 – 0.33—below 0 or above 0.33

No separate Sufficient band is currently defined for this marker.

What the evidence says

The bands are Labcorp's interval for bioavailable testosterone measured by ammonium sulfate precipitation: 40 to 250 ng/dL for men and up to 9.5 ng/dL for women, with no low edge for women. Mayo's intervals fall with age in men, from 83 to 257 ng/dL in the twenties to 40 to 168 in the sixties, so a young man near the bottom of this band would be low at Mayo; Sera has no age-specific rows yet. The nmol/L rows are conversions; no UK or European interval was found. A bioavailable testosterone calculated from total testosterone, SHBG and albumin does not always agree with the measured one. No source supports a narrower optimal range.

Assay: Results differ meaningfully between platforms and methods. Compare against the interval printed by the issuing laboratory before acting on a borderline value.

Sources

  • Testosterone, Free and Weakly Bound (143255) — Labcorp, 2026 · Laboratory / reference-interval sourceBioavailable testosterone by ammonium sulfate precipitation: men 40 to 250 ng/dL, women 0 to 9.5 ng/dL. Sera's bands.
  • Testosterone, Free and Weakly Bound, With Total Testosterone, LC/MS-MS (FFTST; Labcorp 070282) — Labcorp (performing laboratory), Kootenai Health Laboratory catalog, 2026 · Laboratory / reference-interval sourceThe same Labcorp intervals, with total testosterone by LC-MS/MS: men 40 to 250 ng/dL, women 0 to 9.5 ng/dL.
  • Testosterone, Total and Bioavailable, Serum (TTBS) — Mayo Clinic Laboratories (performing laboratory), Torrance Memorial Laboratories catalog, 2026 · Laboratory / reference-interval sourceMen's intervals fall by decade, from 83 to 257 ng/dL at 20 to 29 down to 40 to 168 at 60 to 69; women 20 to 50 not on oral oestrogen 0.80 to 10 ng/dL. Context for the age effect Sera's single band does not capture.

What Testosterone (Bioavailable) measures

Free testosterone plus the testosterone loosely bound to albumin: the part not held by SHBG and available to tissues.

Useful when SHBG is high or low, which makes total testosterone misleading. Men's levels fall with age. Laboratories measure it by precipitation or calculate it from total testosterone, SHBG and albumin, and the two methods do not always agree, so compare results from the same method.

Related hormone health markers

See Bioavailable testosterone in the full list of biomarker ranges

About the author

Alina Radu is the founder of Sera and a software engineer. The idea started with her own Hashimoto's tests, scattered across years without the big picture. She is not a clinician: these ranges are compiled from the published sources linked on each page, with every source named. Alina Radu on LinkedIn

This page is a reference for practitioners, not medical advice. Sera's bands are practitioner targets for structured review, not diagnostic thresholds, and Sera does not diagnose or recommend treatment. Read a result alongside the interval printed by the issuing laboratory and the client's history and symptoms. Range set: Sera Production, version 1.0, last reviewed November 9, 2026.