Androgens . Patient guide
Free Testosterone
Free testosterone is the small, biologically active fraction of testosterone that is not bound to plasma proteins. It is a useful complement to total testosterone, particularly when SHBG (the binding protein) is abnormal, because it reflects what tissues can actually use.
This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).
Reference range
Reported in nmol/L. Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.
| Group | Range | Note |
|---|---|---|
| Adult men | 0.20 to 0.62 | nmol/L (calculated; varies between methods) |
| Adult women | 0.005 to 0.030 |
What it is
Most testosterone in blood is bound to sex-hormone binding globulin (SHBG) and albumin. Only the unbound (“free”) portion, plus the loosely albumin-bound portion (together called “bioavailable testosterone”), is available to receptors.
Why a clinician would order it
Used when total testosterone is borderline or when SHBG is high (older men, hyperthyroidism, oestrogen exposure) or low (obesity, insulin resistance, hypothyroidism). Particularly useful where symptoms suggest low androgen activity despite a normal total testosterone.
If your level is outside the range
Symptoms of low Free Testosterone
- Same as low total testosterone, with stronger correlation when SHBG is abnormal
What low can indicate. Same causes as low total testosterone, plus raised SHBG masking what is actually a low free fraction.
Symptoms of high Free Testosterone
- In women: features of androgen excess (acne, hirsutism, hair thinning). In men: usually exogenous administration.
What high can indicate. Androgen excess (PCOS / PMOS, congenital adrenal hyperplasia, androgen-secreting tumour) or exogenous testosterone use.
Testing tips
Morning sample. Both total and free testosterone should be measured at the same time to allow comparison. Some labs report calculated free testosterone from total testosterone + SHBG + albumin; others measure it directly.
Where you can get this tested
Free Testosterone is included in the following WMG Health panels. Same-day appointments at our Harley Street clinic, with results clinician-reviewed.
Want a specific combination of markers we do not have a panel for? Build a custom panel and our clinicians will design one for you.
Related markers
Sources
UK guidance our clinicians use when interpreting this marker.
This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.