Free Testosterone
This measures the small fraction of testosterone that's actually available to enter your cells — the part that drives muscle, libido, mood, and energy.
Only 2–3% of your total testosterone floats freely in blood — unbound to any protein. This free fraction is what actually enters muscle, brain, and bone cells. A man with "normal" total T but high SHBG can have very low free T and experience all the symptoms of low testosterone.
Good for you if: Your total testosterone looks "normal" but you still have symptoms (fatigue, low libido, poor recovery), or you suspect high SHBG is binding up your testosterone.
Dive deeper into the scienceWhat is this test?
Free testosterone is the unbound fraction of total testosterone circulating in your blood. About 44% of your total testosterone is locked up by SHBG (sex hormone binding globulin) — essentially inactive. Another 54% is loosely bound to albumin (weakly active). The remaining 2–3% floats freely and can enter cells to activate androgen receptors.
This is the testosterone that builds muscle, supports libido, maintains bone density, and keeps your mood sharp. Two men with identical total testosterone can feel completely different if one has low SHBG (lots of free T) and the other has high SHBG (most T is locked away).
What your number means
| Free Testosterone | What it means | What to do |
|---|---|---|
| <5 pg/mL | Very low — likely symptomatic | Physician evaluation; check SHBG, total T, LH |
| 5–10 pg/mL | Low — borderline | Address SHBG if elevated; lifestyle optimisation; boron supplementation |
| 10–15 pg/mL | Adequate — room to improve | Optimise sleep, training, nutrition; consider boron and tongkat ali |
| 15–25 pg/mL | Optimal | Maintain; test annually |
| >25 pg/mL | High-normal | Great if natural; monitor if on TRT |
Note: units vary between labs. Some report in ng/dL (multiply pg/mL by 0.1 to convert). The numbers above use pg/mL, the most common unit in Indian labs. Always compare against the lab's specific reference range and methodology.
How to improve it
Lower SHBG if elevated — high SHBG is the most common cause of low free T with normal total T. Boron 6–10mg daily can reduce SHBG by 10–20%. Ensure adequate carbohydrate intake — very low carb and keto diets raise SHBG.
Raise total testosterone — since free T is a fraction of total T, all the interventions that raise total T (sleep, resistance training, fat loss, stress management) also raise free T.
Address insulin resistance — insulin suppresses SHBG, so insulin resistance can cause paradoxically low SHBG and higher free T, but with poor metabolic context. Fix the root cause.
- Boron — 6–10mg daily; the strongest evidence for lowering SHBG and raising free T
- Tongkat Ali — 200–400mg daily; may reduce SHBG and support free testosterone
- Magnesium — 200–400mg glycinate; supports testosterone and may modulate SHBG
- Nettle root extract — may bind to SHBG, freeing up testosterone (limited but promising evidence)
- Adequate carbs — very low carb diets (under 100g/day) increase SHBG; include sufficient starchy carbs around training
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Get early accessFrequently Asked Questions
What is a good free testosterone level?
Optimal free testosterone for men under 50 is 15–25 pg/mL (direct measurement) or 2–3% of total testosterone. Labs often report "normal" down to 5 pg/mL — that's too low. If your total T is 600 ng/dL but free T is only 8 pg/mL, your SHBG is likely high and locking up most of your testosterone.
Why is free testosterone more important than total?
Total testosterone includes the 97–98% that's bound to SHBG and albumin — it can't enter cells in that form. Free T is the fraction that actually binds to androgen receptors and produces effects: muscle growth, libido, mood, bone density. You can have "normal" total T but low free T and be fully symptomatic.
How do I lower SHBG to increase free testosterone?
Boron 6–10mg daily has the strongest evidence for reducing SHBG. Ensuring adequate carbohydrate intake (very low carb diets raise SHBG), managing insulin resistance, and tongkat ali 200–400mg may also help. Avoid excessive alcohol. But first verify your SHBG is actually elevated — low SHBG has its own problems.
Should I test free testosterone or calculated free T?
Direct measurement by equilibrium dialysis is the gold standard but expensive and not widely available. Most labs either measure by analog immunoassay (less accurate) or calculate free T from total T, SHBG, and albumin using the Vermeulen equation. Calculated free T is reliable enough for clinical decisions.
How it's measured
Free testosterone can be measured directly (equilibrium dialysis or ultrafiltration — gold standard but expensive) or calculated from total T, SHBG, and albumin using the Vermeulen equation. Most Indian labs use either analog immunoassay (less reliable) or calculated free T. For accurate results, ensure you're getting total T and SHBG in the same draw so free T can be properly calculated.
Clinical ranges vs optimal ranges
Lab reference ranges for free T (typically 5–21 pg/mL) were derived from population studies including older and unhealthy men. For a man under 50, the lower half of "normal" is often symptomatic. Longevity-optimised targets are 15–25 pg/mL — representing adequate androgenic signalling for muscle maintenance, bone health, and cognitive function.
India-specific considerations
Free testosterone testing availability varies across Indian labs. Many labs don't offer equilibrium dialysis and rely on less accurate analog immunoassay. The better approach in India is to test total T + SHBG + albumin and use an online Vermeulen calculator. This gives a more reliable calculated free T than most direct assays available domestically.
Vegetarian diets (common in India) tend to raise SHBG slightly, which can lower free T relative to total T. This makes free T testing particularly relevant for Indian vegetarian men with borderline total T who might have even lower bioavailable testosterone than expected.
Connected supplements
- Boron — 6–10mg daily; reduces SHBG by 10–20%, directly increasing free T fraction
- Tongkat Ali — 200–400mg daily; may lower SHBG and support free testosterone
- Ashwagandha (KSM-66) — 600mg daily; raises total T which increases free T proportionally
- Zinc — 25–30mg daily; supports testosterone synthesis; common deficiency in vegetarians
- Stinging nettle root — may competitively bind SHBG, freeing up testosterone
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