Free Testosterone Test: Ranges, Low and High Results, Methods and What It Means

Most circulating testosterone is bound to SHBG or albumin. Free testosterone is the unbound fraction. Total testosterone includes free and protein-bound hormone. Bioavailable testosterone usually combines free and weakly albumin-bound testosterone, so it is a different analyte.^{See reference 10,See reference 14}

Calculated free testosterone is an estimate made from total testosterone, SHBG and albumin using a named binding equation. Percent free testosterone is a percentage, while free-androgen index is usually 100 × total testosterone divided by SHBG. Neither should be relabelled as a measured free-testosterone concentration.^{See reference 3,See reference 4,See reference 11}

DHT and DHEA-S are also different hormones. A result is most informative when its exact analyte, method, unit and related markers stay attached to it.^{See reference 4,See reference 14}

For testosterone, 1 pg/mL equals 3.4672 pmol/L. Also, 1 ng/dL equals 10 pg/mL and 34.672 pmol/L. For example, 50 pg/mL equals 173.4 pmol/L. Preserve the original value and round only the displayed result.^{See reference 9}

This local converter sends no value for interpretation. It applies only to an absolute free-testosterone concentration. It cannot convert percent free, FAI or bioavailable testosterone; identify an assay; calculate free testosterone; apply a universal range; diagnose a condition; or choose a dose. A converted number must still use the original method-specific laboratory interval.^{See reference 1,See reference 4,See reference 8,See reference 9}

Low production can originate in the testes or ovaries, or in hypothalamic and pituitary signalling. Aging, acute or chronic illness, undernutrition, major energy deficit, obesity, sleep disruption, glucocorticoids, opioids and other medicines can contribute. Exogenous testosterone or anabolic steroids can suppress the body's own LH and FSH signalling.^{See reference 1,See reference 3,See reference 15}

High SHBG can lower the free fraction even when total testosterone looks less affected. Thyroid and liver conditions, estrogen exposure, HIV and some anticonvulsants are examples. An inaccurate assay or calculation can also create an apparently low value.^{See reference 1,See reference 3,See reference 11}

Fatigue, lower libido, mood change, erectile difficulty, menstrual change and body-composition concerns are not specific to testosterone. Diagnosis in men requires compatible symptoms or signs plus consistently low accurate testosterone results; other sexes and life stages require their own clinical framework.^{See reference 1,See reference 2,See reference 4,See reference 14}

Prescribed testosterone, anabolic-androgen use, sample timing near a treatment peak and low SHBG are common interpretive possibilities. A high value may also reflect assay interference or a calculation that performs poorly in the person's binding state.^{See reference 1,See reference 11,See reference 17,See reference 18}

In women, ovarian or adrenal androgen excess can contribute. PCOS is common, but rapid progressive virilization or a severe biochemical elevation needs prompt specialist evaluation for less common ovarian or adrenal causes. Free testosterone alone does not diagnose PCOS or a tumour.^{See reference 4,See reference 5}

A high result is not proof of better health and is not a reason to increase a dose. Confirm the analyte, method, unit, laboratory interval, collection timing and related hormones before drawing a conclusion.^{See reference 1,See reference 4,See reference 8}

The safe goal is to identify and address the cause—not to maximize a number. Sleep, adequate energy intake, body-composition changes and management of relevant illness or medicines may improve a reversible pattern for some people, but expected effects vary and do not replace repeat diagnostic testing.^{See reference 1,See reference 3}

Clinician-managed testosterone can be appropriate for defined indications after accurate diagnosis, contraindication review and shared decision-making. Monitoring is formulation- and patient-specific. A free-testosterone result cannot select a dose or prove that benefits exceed fertility, blood-count, cardiovascular, prostate or exposure risks.^{See reference 1,See reference 2,See reference 15,See reference 17}

Do not self-start testosterone, anabolic steroids, hCG, SERMs, aromatase inhibitors or unverified boosters from one value. Do not stop prescribed hormones, contraception or other medicines without the prescriber; changing them can alter symptoms, fertility and the next test.^{See reference 1,See reference 4,See reference 15}