Free Testosterone (FT)
Also known as: FT
Free testosterone is the unbound, biologically active fraction of testosterone. It correlates more closely with symptoms than total testosterone and is essential context whenever SHBG is high or low.
What Free Testosterone measures
Free testosterone measures the small unbound fraction of circulating testosterone — the portion biologically available to bind androgen receptors. It is typically reported as either a calculated value (from total testosterone + SHBG + albumin) or a direct equilibrium dialysis measurement.
Clinical significance
Symptoms of androgen insufficiency correlate more reliably with free testosterone than with total testosterone, especially in the presence of altered SHBG. Men with normal total testosterone but low free testosterone routinely present with low libido, fatigue, and reduced recovery — a pattern provider review catches only when both markers are evaluated together.
How oMeds reviews it
Inside the Hormone Optimization pathway, free testosterone is co-equal with total testosterone for decision-making. A discordant pair (normal total, low free) triggers a confirmatory SHBG and estradiol draw before any therapy conversation. Optimization targets the upper-mid free testosterone reference range while estradiol and hematocrit remain in band.
Standard clinical reference intervals
Lab-reported reference ranges from established standards bodies. These are diagnostic thresholds — they do not represent optimization targets.
Source: LabCorp adult male reference interval (equilibrium dialysis)
Morning draw preferred. Calculated values vary by formula.
Source: LabCorp adult female reference interval
oMeds optimization targets
Editorial bands that inform provider-reviewed conversations. These are wellness targets, not diagnostic thresholds.
Provider-reviewed symptom resolution in optimization most consistently maps to free testosterone in the upper-mid reference range, with SHBG and estradiol balanced.
oMeds optimization ranges are editorial targets that inform conversations with a licensed provider. They are NOT diagnostic thresholds and do not replace lab reference ranges.
Free Testosterone — frequently asked
Is calculated or direct free testosterone better?
Direct equilibrium dialysis is the gold standard but more expensive. Calculated free testosterone (from total testosterone, SHBG, and albumin) is acceptable when SHBG is in the normal range. oMeds defaults to calculated and orders direct measurement when SHBG is markedly high or low.
Why might my free testosterone be low if my total testosterone is normal?
Elevated SHBG binds testosterone tightly, lowering the free fraction. SHBG rises with thyroid hormone, estrogen, aging, and certain medications. Provider review pairs free testosterone, total testosterone, SHBG, and symptoms before reaching a conclusion.
Source literature
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