Free Testosterone
The fraction of testosterone not bound to proteins, available to act on tissues.
| Typical reference range (male) | 46–224 pg/mL |
| Typical reference range (female) | 0.2–5 pg/mL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Free testosterone is the 1-3% of testosterone not bound to SHBG or albumin. It can be measured by equilibrium dialysis, calculated from total testosterone, SHBG and albumin (Vermeulen equation), or measured by direct analog immunoassay, which is less accurate.
Why it matters
Free testosterone better reflects androgen activity when SHBG is abnormally high or low, such as with obesity, aging, liver disease, thyroid disorders or certain medications.
What a high result can mean
High levels occur with testosterone or anabolic steroid use, low SHBG (obesity, insulin resistance), and in women with PCOS or other androgen excess conditions.
What a low result can mean
Low levels occur with hypogonadism and with high SHBG from aging, hyperthyroidism, liver disease, low-calorie diets, estrogen use or anticonvulsants.
What affects the result
Reference ranges differ greatly between methods: dialysis/calculated methods (Quest ~46-224 pg/mL in men) versus direct immunoassay (Labcorp ~8.7-25 pg/mL in men), so compare only within the same method. Morning testing is recommended.
Units and conversion
Usually reported in pg/mL.
- From ng/dL: multiply by 10 to get pg/mL
- From pmol/L: multiply by 0.288 to get pg/mL
- From nmol/L: multiply by 288.4 to get pg/mL
- From ng/mL: multiply by 1,000 to get pg/mL
Also called on lab reports
Testosterone, Free, Testosterone, Free (Direct), Free Testosterone (Direct), Testosterone, Free, Calculated, Free Testosterone, Calculated, Testosterone Free, Testosterone, Free, Equilibrium Dialysis, Free Testosterone (Calc)
Related tests: Sex Hormones
This page is educational and does not replace advice from a healthcare professional.