What it measures
Free testosterone is the small part of testosterone that is not bound to proteins in the blood. This result is worked out by the lab from total testosterone, SHBG and albumin using a standard formula, rather than measured directly. It gives a clearer picture than total testosterone when SHBG is high or low.
Why people test it
- Used when total testosterone is borderline, to see how much is free.
- Checked when symptoms such as low sex drive or erection problems are being looked into.
- Useful when SHBG is high or low, as can happen with age, weight or thyroid conditions.
- Monitored on TRT alongside total testosterone and SHBG.
- Checked after anabolic steroid use, which can suppress natural testosterone production for months.
Typical range
Ranges vary by lab, formula, age and sex, and the result depends on the lab's testosterone and SHBG methods. Your report shows the lab's own range.
Finger-prick or vein?
A vein sample is usually advised. Finger-prick results can be raised by creams or gels on the fingers, especially testosterone gel.
Testosterone is highest in the morning, so samples are usually taken before 11am.