What is the normal range for a woman's testosterone level?

Normal Testosterone Levels in Women

The normal range for total testosterone in women is approximately 15-46 ng/dL (0.52-1.60 nmol/L), with free testosterone ranging from 1.2-6.4 pg/mL (4.16-22.2 pmol/L). 1

Reference Ranges for Female Testosterone

Female testosterone levels are significantly lower than male levels, with a clear bimodal distribution between sexes:

• Total Testosterone:

  • Women: 15-46 ng/dL (0.52-1.60 nmol/L) 1
  • Men: 300-950 ng/dL (10.41-32.96 nmol/L) 2

• Free Testosterone:

  • Women: 1.2-6.4 pg/mL (4.16-22.2 pmol/L) 1
  • Men: 50-200 pg/mL 2

This represents a 4-5 fold difference between the upper limit of the normal female range and the lower limit of the normal male range 3.

Age and Cycle Considerations

• Testosterone levels in women exhibit an age-related decline 1
• While there are small variations across the menstrual cycle, these are relatively minor compared to overall variability, allowing reference ranges to be applied regardless of cycle timing 1
• Sex hormone-binding globulin (SHBG) levels remain relatively stable across age ranges in premenopausal women, with reference ranges of 18-86 nmol/L 1

Clinical Implications

Diagnosing Hyperandrogenism

The detection of hyperandrogenism in women is challenging when using inappropriate reference ranges:

• Commercial laboratory reference ranges often use approximately 10-90 ng/dL as the normal range 4
• These ranges are too broad and may miss clinically significant hyperandrogenism
• Studies show most hyperandrogenic women have testosterone levels >50 ng/dL, while most normal women have levels <40 ng/dL 4
• Using more accurate reference ranges with an upper limit of 28 ng/dL provides 84% sensitivity for detecting hyperandrogenemia 5

Testing Considerations

When measuring testosterone in women:

• Morning samples are preferred for consistency 1
• Multiple testing methodologies exist, including:
  • Reference methods: equilibrium dialysis and ultrafiltration
  • Analog immunoassay
  • Calculated free testosterone based on total testosterone, SHBG, and albumin measurements 6
• Consider measuring both total and free testosterone, as the free fraction represents the metabolically active portion 6

Common Pitfalls to Avoid

1. Using inappropriate reference ranges: Commercial laboratory ranges are often too broad and may miss clinically significant hyperandrogenism 4, 5

2. Relying solely on total testosterone: Free testosterone measurements may be more clinically relevant in some cases, as this represents the metabolically active fraction 6

3. Inconsistent laboratory methods: Different assay kits can produce significantly different results for the same sample (e.g., a sample with mean testosterone of 96.1 ng/dL might be reported as 71.8-123.4 ng/dL by different labs) 4

4. Ignoring timing of sample collection: While variations across the menstrual cycle are relatively small, morning samples are still preferred for consistency 1

By using appropriate reference ranges and understanding the limitations of testing methods, clinicians can more accurately diagnose conditions of androgen deficiency or excess in women.