What is a normal testosterone level?

The harmonized reference range

A 2017 study — Travison, Vesper, Orwoll, et al., The Journal of Clinical Endocrinology & Metabolism, 102(4):1161–1173 — pooled four cohorts of healthy nonobese men aged 19–39 and, after standardizing to a CDC reference method, reported these total-testosterone percentiles: 2.5th 264, 5th 303, 50th (median) 531, 95th 852, 97.5th 916 ng/dL. The 264–916 ng/dL span between the 2.5th and 97.5th percentiles is the commonly cited “normal” range.

The diagnostic threshold guidelines use

The 2018 Endocrine Society Clinical Practice Guideline (Bhasin et al., JCEM 103(5):1715–1744) adopts 264 ng/dL — the lower limit of that harmonized range — as the threshold below which, with consistent symptoms and a repeat morning measurement, hypogonadism is considered. These figures are reported as the sources state them, not as a personal target.

Why ranges vary by lab and assay

The Travison paper is explicit that lab results are not directly comparable: “A substantial proportion of intercohort variation in testosterone levels is due to assay differences.” Before harmonization, three cohorts of men aged 40–49 measured 501, 551, and 618 ng/dL; after standardizing to the CDC method they converged to 487, 494, and 471. A given lab's reference interval depends on its assay and population — which is why the harmonized range exists, and why an individual result is read against the reporting lab's own range.

• Harmonized normal range (Travison 2017, healthy nonobese men 19–39): 264–916 ng/dL, median 531.
• Endocrine Society 2018 lower diagnostic threshold: 264 ng/dL.
• Results vary by lab and assay — read against the reporting lab's own reference interval.