Free testosterone (direct)

What it measures, and what changes the number.

This test measures unbound testosterone directly in the sample, rather than calculating it from total testosterone and SHBG. Free testosterone is the fraction not attached to SHBG or albumin.

It is usually read alongside total testosterone and SHBG. Some reports also give calculated free testosterone, which allows the two approaches to be compared.

The method strongly affects the number. Equilibrium dialysis and ultrafiltration are considered reference approaches. Direct analog immunoassays are simpler, but they are known to agree poorly with those methods. Results from different methods are therefore hard to compare. Testosterone is highest in the morning, so samples are typically drawn early in the day. Reports may print it as Free Testosterone, TESTOSTERONE, FREE or Testosterona Libre.

Reference ranges labs publish

Each lab states an interval for its own method and the population it measured. They differ, they are not interchangeable, and none of them is a verdict on a single result.

• Men, 20 to 24 years: 5.25 to 20.7 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 25 to 29 years: 5.05 to 19.8 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 30 to 34 years: 4.85 to 19 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 35 to 39 years: 4.65 to 18.1 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 40 to 44 years: 4.46 to 17.1 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 45 to 49 years: 4.26 to 16.4 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 50 to 54 years: 4.06 to 15.6 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 55 to 59 years: 3.87 to 14.7 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 60 to 64 years: 3.67 to 13.9 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 65 to 69 years: 3.47 to 13 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 70 to 74 years: 3.28 to 12.2 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 75 to 79 years: 3.08 to 11.3 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 80 to 84 years: 2.88 to 10.5 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 85 to 89 years: 2.69 to 9.61 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 90 to 94 years: 2.49 to 8.76 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, 95 years and over: 2.29 to 7.91 ng/dL · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Men, adults: 5 to 21 ng/dL · Equilibrium ultrafiltration · Source: Labcorp, 070038 (Testosterone, Free, Equilibrium Ultrafiltration With Total Testosterone, LC/MS-MS) (read 2026-09-24)
• Men, 20 to 29 years: 9.3 to 26.5 pg/mL · Direct analog immunoassay · Source: Labcorp, 144980 (Testosterone, Free, Direct) (read 2026-09-24)
• Men, 30 to 39 years: 8.7 to 25.1 pg/mL · Direct analog immunoassay · Source: Labcorp, 144980 (Testosterone, Free, Direct) (read 2026-09-24)
• Men, 40 to 49 years: 6.8 to 21.5 pg/mL · Direct analog immunoassay · Source: Labcorp, 144980 (Testosterone, Free, Direct) (read 2026-09-24)
• Men, 50 to 59 years: 7.2 to 24 pg/mL · Direct analog immunoassay · Source: Labcorp, 144980 (Testosterone, Free, Direct) (read 2026-09-24)
• Men, 60 years and over: 6.6 to 18.1 pg/mL · Direct analog immunoassay · Source: Labcorp, 144980 (Testosterone, Free, Direct) (read 2026-09-24)
• Women, 20 to 24 years: up to 1.08 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 25 to 29 years: up to 1.06 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 30 to 34 years: up to 1.03 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 35 to 39 years: up to 1 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 40 to 44 years: up to 0.98 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 45 to 49 years: up to 0.95 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 50 to 54 years: up to 0.92 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 55 to 59 years: up to 0.9 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 60 to 64 years: up to 0.87 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 65 to 69 years: up to 0.84 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 70 to 74 years: up to 0.82 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 75 to 79 years: up to 0.79 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 80 to 84 years: up to 0.76 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 85 to 89 years: up to 0.73 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 90 to 94 years: up to 0.71 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, 95 years and over: up to 0.68 ng/dL (no lower limit stated) · Equilibrium dialysis, LC-MS/MS · Source: Mayo Clinic Laboratories, TGRP (Testosterone, Total and Free, Serum) (read 2026-09-24)
• Women, adults: 0.1 to 0.85 ng/dL · Equilibrium ultrafiltration · Source: Labcorp, 070038 (Testosterone, Free, Equilibrium Ultrafiltration With Total Testosterone, LC/MS-MS) (read 2026-09-24)
• Women, 20 years and over: 0 to 4.2 pg/mL · Direct analog immunoassay · Source: Labcorp, 144980 (Testosterone, Free, Direct) (read 2026-09-24)

Often read alongside: Total testosterone, SHBG, Free testosterone (calculated), Free testosterone %, Albumin

Blood test glossary