Free Testosterone
Bioavailable testosterone not bound to proteins
17 of 22 providers
Sex Hormones (Male)
5.0-21.0 ng/dL, or 1.5-3% of total
What is Free Testosterone?
Free testosterone is the small fraction (1-3%) of testosterone not bound to proteins in your blood. While total testosterone includes hormone bound to SHBG and albumin, only free testosterone can enter cells and exert biological effects. It is the truly "active"form of testosterone.
SHBG (sex hormone binding globulin) binds testosterone tightly and renders it inactive. Albumin binds loosely, allowing some bioavailability. Free testosterone plus albumin-bound testosterone is called "bioavailable testosterone."In men, free T is crucial for muscle, bone, libido, mood, and energy.
Free testosterone is especially important when SHBG is abnormal. High SHBG (from liver disease, aging, hyperthyroidism) lowers free T even with normal total T. Low SHBG (obesity, diabetes, hypothyroidism) raises free T. Always interpret free T alongside total T and SHBG.
When Total Testosterone Lies
- SHBG variability:High SHBG can cause low free T symptoms despite normal total T
- Aging pattern:SHBG rises 1-2% yearly, progressively lowering free T even when total T stable
- Obesity effect:Low SHBG in obesity may mask total T decline while free T appears normal
- Symptom correlation:Free testosterone correlates better with hypogonadal symptoms than total T
- Treatment monitoring:Free T better assesses TRT effectiveness than total T
Optimal vs Standard Ranges
Optimal (Adult Males)15-25 pg/mL▼
- Upper-normal range associated with best energy, body composition, and cognitive function
- Target range for TRT optimization
Normal (Lower Range)9-15 pg/mL▼
- Within reference range but may experience subtle symptoms
- Evaluate SHBG and consider optimization if symptomatic
Low<9 pg/mL▼
- Indicates hypogonadism if symptomatic
- Evaluate LH/FSH to determine primary vs secondary cause
- Consider TRT if symptoms present
High>35 pg/mL▼
- May indicate exogenous testosterone use or very low SHBG
- Very high levels can increase side effect risk on TRT
Scientific Evidence
Free T and Symptoms
European Male Aging Study found free testosterone had stronger correlation with hypogonadal symptoms than total testosterone, particularly for sexual and physical symptoms.
Age-Related Decline
Baltimore Longitudinal Study showed total testosterone declines 1% yearly while free testosterone declines 2-3% yearly due to rising SHBG, making free T decline more clinically relevant.
Calculated vs Measured Free T
Vermeulen equation calculating free T from total T and SHBG correlates well with equilibrium dialysis gold standard and is recommended when direct measurement unavailable.
Source:
Which Providers Test Free Testosterone?
Full Provider Comparison
| Provider | Includes | Annual Cost | Biomarkers |
|---|---|---|---|
 Superpower | ✓ | $199 | 100+ (150 with ratios) |
 WHOOP Advanced Labs | ✓ | $349 | 65 |
 Labcorp OnDemand | — | $398 | 30+ |
| ✓ | $486 | 40+ | |
| ✓ | $444 | 288 | |
| ✓ | $349 | 100+ | |
| ✓ | $761 | 54 | |
 Function Health | ✓ | $365 | 160+ |
| — | $250 | 65 | |
| ✓ | $495 | 70+ | |
| ✓ | $895 | 100+ | |
| ✓ | $1950 | 150+ | |
| ✓ | $375 | 80+ | |
| — | $Varies | 75+ | |
| — | $190 | 100+ | |
| — | $99 | 50 | |
| ✓ | $124 | 60 | |
| ✓ | $199 | 50 | |
| ✓ | $499 | 120+ | |
| ✓ | $4188 | 70-80+ | |
| ✓ | $375 | 85 | |
| ✓ | $700 | 128 |
Frequently Asked Questions
What is Free Testosterone?
Bioavailable testosterone not bound to proteins
What is the optimal range for Free Testosterone?
The standard reference range for Free Testosterone is 5.0-21.0 ng/dL, or 1.5-3% of total. Optimal ranges may differ based on individual health goals and expert recommendations.
Which blood test providers include Free Testosterone?
17 out of 22 blood testing providers include Free Testosterone in their panels. This biomarker is widely available across major providers.
What category does Free Testosterone fall under?
Free Testosterone is categorized under Sex Hormones (Male). This category includes biomarkers that help assess related aspects of health and wellness.
Medical Disclaimer
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
Last reviewed:2026-02-20