Understanding Free Testosterone: Normal vs Optimal Ranges

?What is Free Testosterone?

Free testosterone is the small fraction of testosterone not bound to sex hormone binding globulin (SHBG) or albumin, representing only 1–3% of total testosterone. This unbound fraction is the biologically active form that can enter cells and exert hormonal effects. Free testosterone better reflects biological testosterone activity than total testosterone.

!Why It Matters

Some men have normal total testosterone but low free testosterone due to high SHBG levels — often related to hypothyroidism, ageing, or oestrogen excess. These men may have symptoms of testosterone deficiency despite 'normal' total testosterone. Free testosterone or calculated free testosterone should always be measured alongside total testosterone and SHBG for complete assessment.

Reference Ranges

Lab normal ranges may vary between laboratories. Optimal and longevity targets are based on research literature and should be interpreted with your physician.

Symptoms of Imbalance

• Similar to low total testosterone — fatigue, reduced libido, muscle loss, depression

How to Improve Your Levels

• 1Lower SHBG if it is elevated: reduce alcohol, optimise thyroid function, maintain healthy weight
• 2Boron (6–10 mg/day) may lower SHBG and raise free testosterone
• 3Same lifestyle interventions as for total testosterone

When to Test

Order alongside total testosterone and SHBG when evaluating testosterone status.

Related Biomarkers