Free Testosterone
Free testosterone is the unbound fraction of testosterone that is biologically active and can enter cells to exert its effects. It is a more accurate marker of androgen status than total testosterone when SHBG levels are altered by aging, obesity, liver disease, or estrogen use. Low free testosterone despite normal total values can still cause hypogonadal symptoms.
Units: ng/dL or pg/mL; some labs report pmol/L (pmol/L = ng/dL × 34.7 (1 ng/dL = 10 pg/mL)). Check the units on your report before comparing to any range here.
Optimal range: who says what
Institutions, researchers and practitioners draw the line in different places. Each position is listed with who holds it and, where a document states it, a link. How we verify ranges.
- Named practitionermen 115-155 pg/mL (equilibrium dialysis)Life Extension · Lab Testing Protocol (Suggested Optimal Ranges)Disclosure: Life Extension sells lab panels that appear in our blood-test comparisons.
- Lab reference interval5.0-21.0 ng/dL, or 1.5-3% of totalWhat a lab report flags against. A lab interval is not an optimal target.
Practitioner targets are individual positions, often tighter than guideline ranges. Each was checked against its article before publishing.
17 of 21 itemized panels
Sex Hormones (Male)
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
Interpretation bands (curated, PMID-backed)
Holder: OptimizeBiomarkers editorial synthesis of: A critical evaluation of simple methods for the estimation of free testosterone in serum (Vermeulen et al., 1999); Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline (Bhasin et al., 2018). No single paper sets these cutoffs; for attributed targets see who says what.
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
What raises or lowers Free Testosterone
Causes of high Free Testosterone
- Exogenous testosterone/anabolic steroids
- Very low SHBG (obesity, insulin resistance)
- Androgen-secreting tumors (rare)
- Congenital adrenal hyperplasia
Causes of low Free Testosterone
- Aging (gradual decline)
- Obesity
- Type 2 diabetes
- Opioid medications
- Glucocorticoids
- Pituitary disorders
- Testicular injury
- Klinefelter syndrome
Symptoms when Free Testosterone is high or low
When high
- Acne
- Hair loss (scalp)
- Increased body hair
- Aggression
- Mood swings
- Sleep apnea worsening
- Polycythemia risk
Usually only seen with exogenous testosterone. Endogenous production is tightly regulated.
When low
- Decreased libido
- Erectile dysfunction
- Fatigue
- Reduced muscle mass
- Increased body fat
- Depressed mood
- Brain fog
- Decreased motivation
Symptoms develop gradually and may be attributed to aging. Many men adapt without realizing decline.
How to move Free Testosterone
Effect sizes (how much something moves the marker) appear only where the paper cited under the item states them. Talk to your clinician before starting or changing any medication or supplement.
Resistance Training
Compound lifts (squats, deadlifts, bench press) acutely boost testosterone. Training volume and intensity matter. Overtraining decreases testosterone.
Sleep Optimization
Testosterone is produced during sleep. The National Sleep Foundation recommends 7-9 hours for adults. One week of restricted sleep lowered testosterone in young healthy men (Leproult 2011).
Source: Effect of 1 week of sleep restriction on testosterone levels in young healthy men.
Manage Body Fat
Adipose tissue converts testosterone to estrogen via aromatase. Losing excess body fat tends to raise testosterone in men with obesity.
Reduce Chronic Stress
Cortisol and testosterone have inverse relationship. Chronic stress suppresses GnRH and reduces testosterone production. Stress management is crucial.
Consider TRT if Indicated
If lifestyle optimization fails and symptoms persist with low free T, testosterone replacement therapy can restore levels. Requires ongoing monitoring.
When to retest
- Test in morning (8-10 AM) when levels peak
- Retest in 2-4 weeks if borderline - testosterone varies from day to day
- Check LH, FSH if low to determine primary vs secondary cause
- Calculate free T from total T and SHBG if direct measurement unavailable
Scientific Evidence
Free T and Symptoms
The European Male Ageing Study of 3,369 men aged 40-79 found that three sexual symptoms (poor morning erections, low desire, erectile dysfunction) tracked low testosterone. It defined late-onset hypogonadism as those symptoms plus total testosterone below 11 nmol/L (3.2 ng/mL) and free testosterone below 220 pmol/L (64 pg/mL).
Source: Identification of late-onset hypogonadism in middle-aged and elderly men.
Age-Related Decline
In the Massachusetts Male Aging Study, total testosterone fell 0.8% per year of age cross-sectionally while free testosterone fell about 2% per year, as SHBG rose 1.6% per year. Within the same men followed 7-10 years, total testosterone fell 1.6% a year and bioavailable testosterone 2-3% a year.
Calculated vs Measured Free T
Free testosterone calculated from total testosterone and SHBG was almost identical to the equilibrium dialysis value in all conditions studied except pregnancy. Direct analog immunoassays of free testosterone and the free androgen index were not reliable.
Source: A critical evaluation of simple methods for the estimation of free testosterone in serum.
Which Providers Test Free Testosterone?
Cheapest: Mito Health at $297/year. Most comprehensive: Function Health, 160+ biomarkers for $365/year.
17 panels that include it, cheapest first
| Provider | Annual Cost | Total Biomarkers | $/Biomarker |
|---|---|---|---|
| $297 | 100+ | $2.97 | |
 Superpower | $349 | 100+ | $3.49 |
| $349 | 75+ | $4.65 | |
 WHOOP Advanced Labs | $349 | 65 | $5.37 |
 Function Health | $365 | 160+ | $2.28 |
| $365 | 100+ | $3.65 | |
| $375 | 108 | $3.47 | |
| $449 | 83 | $5.41 | |
| $495 | 80+ | $6.19 | |
| $499 | 100+ | $4.99 | |
| $700 | 138 | $5.07 | |
| $829 | 54 | $15.35 | |
| $895 | 100+ | $8.95 | |
| $996 | 59 | $16.88 | |
| $1188 | 70+ | $16.97 | |
| $1198 | 40+ | $29.95 | |
| $1950 | 130+ | $15.00 |
$/Biomarker is annual cost divided by the panel's advertised biomarker count, not the price of this one test. We track 23 blood test providers (32 plans); 21 of those plans are itemized marker by marker. Compare all of them.
4 itemized panels do not include Free Testosterone
Labcorp OnDemand · Marek Health Base · Empirical Health · Oura Health Panels
11 providers not itemized in our matrix
We have not itemized these marker by marker (some sell tests one at a time), so this page cannot say whether they offer Free Testosterone. Check with them directly.
Life Extension Standard · Quest Health · Ultrahuman Blood Vision · Lifeforce · Hundred Health · Personalabs · Walk-In Lab · HealthLabs · WHOOP Specialized Panels · Marek Health Essential · Vitality Blueprint Upload
Experts discussing Free Testosterone
Podcast episodes where clinicians and researchers cover this marker in depth. Curated by hand; an episode is listed only when the marker is a substantial topic, not a passing mention.
Frequently Asked Questions
What is the optimal range for Free Testosterone?
Named practitioners target: men 115-155 pg/mL (equilibrium dialysis) (Life Extension). Lab reference interval: 5.0-21.0 ng/dL, or 1.5-3% of total. That is what a lab report flags against, not an optimal target.
Which blood test providers include Free Testosterone?
17 of the 21 blood testing panels we itemize marker by marker include Free Testosterone in their panels. This biomarker is widely available across major providers.
Related: YouBoost rates lifestyle and supplement interventions by evidence; HRV Zone tracks recovery trends.
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 Sep 23, 2026 · First published Sep 30, 2025