What is the normal reference range for free testosterone in a healthy premenopausal woman (regular menstrual cycles, age 18‑49 years) in pg/dL?

Normal Free Testosterone Range in Premenopausal Women

For a healthy premenopausal woman (age 18–49 years with regular menstrual cycles), free testosterone measured by equilibrium dialysis typically ranges from approximately 1.2 to 6.4 pg/mL (4.16 to 22.2 pmol/L), with values peaking at mid-cycle around 15.6 pg/mL. 1, 2

Reference Ranges by Measurement Method

Equilibrium Dialysis (Gold Standard)

• Free testosterone: 1.2–6.4 pg/mL (4.16–22.2 pmol/L) for a typical 30-year-old woman 1
• Mid-cycle peak values can reach approximately 15.6 ± 11.9 pg/mL, which is higher than previously reported in older literature 2
• The 5th to 95th percentile range was established in 161 healthy women aged 18–49 years with normal menstrual cycles 1

Calculated Free Testosterone

• Calculated free testosterone: 1.3–5.6 pg/mL (4.5–19.4 pmol/L) for a 30-year-old woman 1
• This method uses total testosterone and SHBG measurements to estimate free testosterone 1

Age-Specific Considerations

• Free testosterone declines with age across the premenopausal years, even in women with regular cycles 1, 3
• For women aged 20–80 years measured by mass spectrometry, the reference range for free testosterone is 0.0025–0.0253 nmol/L (approximately 0.72–7.3 pg/mL when converted) 3

Menstrual Cycle Variation

Follicular to Mid-Cycle Changes

• Free testosterone increases progressively across the follicular phase and peaks at mid-cycle, coinciding with ovulation 2
• The mid-cycle peak (approximately 15.6 pg/mL) is substantially higher than early follicular phase values 2

Luteal Phase

• Free testosterone gradually declines during the luteal phase after the mid-cycle peak 2
• Despite this variation, the overall reference ranges can be applied irrespective of menstrual cycle day because the mid-cycle increase is relatively small compared to overall inter-individual variability 1

Supporting Total Testosterone Values

For context, the corresponding total testosterone ranges in premenopausal women are:

• 15–46 ng/dL (520–1595 pmol/L) for a 30-year-old woman 1
• Mid-cycle peak: approximately 43.6 ± 16.2 ng/dL 2
• Age 20–80 years: 0.35–1.97 nmol/L (approximately 10–57 ng/dL) 3

Critical Measurement Considerations

Importance of Accurate Methodology

• Equilibrium dialysis coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the gold standard for measuring free testosterone in women 2
• Traditional immunoassays offer limited precision and specificity in the low concentration range typical of women and should be avoided 3

Bioavailable Testosterone

• Bioavailable testosterone: 1.12–7.62 ng/dL (38.8–264.21 pmol/L) represents testosterone not bound to SHBG and is another measure of biologically active androgen 1

SHBG Reference Range

• SHBG: 18–86 nmol/L in premenopausal women, which remains relatively stable across age ranges 1

Clinical Pitfalls to Avoid

• Do not use direct immunoassay methods for free testosterone measurement in women, as they lack accuracy in the low concentration range 3
• Do not assume a single reference range applies to all ages—free testosterone declines significantly with age even in healthy premenopausal women 1, 3
• Be aware that mid-cycle values can be substantially higher (up to 15.6 pg/mL) than previously reported ranges, which may lead to misdiagnosis of hyperandrogenism if menstrual phase is not considered 2
• Recognize that women have a DHT-to-testosterone ratio of approximately 1:4, which is significantly higher than the 1:13 ratio in men, though the clinical significance of this difference requires further investigation 2