A testosterone level of 18 ng/dL in a 48-year-old woman is within the normal range and does not require treatment based solely on this value.
The decision to treat depends entirely on whether she has symptoms of androgen deficiency (diminished well-being, persistent fatigue, decreased sexual desire) in the context of adequate estrogen status, not on the testosterone number alone 1, 2.
Understanding the Reference Range
The testosterone level of 18 ng/dL falls within established normal ranges for women in this age group:
- For a 30-year-old woman, the 5th to 95th percentile range is 15-46 ng/dL 3
- Age-related decline is expected: Testosterone levels decline by approximately 50% from the early 20s to mid-40s 2, with steep declines occurring in the early reproductive years 4
- At age 48, this woman is in the perimenopausal/early menopausal transition where testosterone levels naturally overlap substantially between menstruating and postmenopausal women 1
Recent large-scale data from 2026 shows that in postmenopausal U.S. women, the weighted mean total testosterone was 25.2 ng/dL, with 56% having levels <20 ng/dL 5. Your patient's level of 18 ng/dL is therefore not abnormally low for her age.
Clinical Decision Algorithm
Step 1: Assess for Symptoms
Does she have the triad of:
- Diminished sense of well-being
- Persistent unexplained fatigue
- Decreased sexual desire, receptivity, and pleasure
If NO symptoms → No treatment indicated 1, 2
Step 2: Verify Estrogen Status
Is she estrogen-replete? (Either naturally cycling or on adequate estrogen replacement if postmenopausal)
If estrogen-deficient → Address estrogen first, not testosterone 2
Step 3: Rule Out Other Causes
Have you excluded:
- Depression, anxiety, relationship issues
- Medications (SSRIs, oral contraceptives, oral estrogens)
- Thyroid dysfunction
- Chronic medical conditions
- Sleep disorders
If other causes present → Address those first 1
Step 4: Consider Assay Reliability
Was testosterone measured by:
- Liquid chromatography-tandem mass spectrometry (LC-MS/MS), OR
- A validated specialty laboratory assay?
Standard automated hospital immunoassays are often inadequate for measuring testosterone in women 6. If using a standard lab assay and clinical suspicion remains high, consider retesting with a more reliable method 6.
Step 5: Assess Free Testosterone
If total testosterone is borderline and symptoms are present, calculate or measure free testosterone, as it may be more sensitive for detecting androgen deficiency 6.
Important Caveats
Timing of measurement matters but is less critical than previously thought: While guidelines recommend early morning, follicular phase sampling for standardization 6, the midcycle rise in testosterone is modest and the between-woman variability is substantial 1. The variation across the menstrual cycle (approximately 25%) is small compared to overall population variability 3.
Natural menopause itself does not significantly lower testosterone: Most prospective studies show no significant change in testosterone levels across the menopausal transition 1, 4. The age-related decline is more important than menopausal status per se.
Race/ethnicity affects distribution: Non-Hispanic Asian and Mexican American women have higher proportions with lower testosterone levels compared to Non-Hispanic Black women 5, though clinical significance of these differences is unclear.
When NOT to Treat
- Asymptomatic women with low-normal testosterone
- Women with symptoms but other identifiable causes
- Women who are estrogen-deficient (treat estrogen deficiency first)
- Women with inadequately assessed testosterone (unreliable assay method)
Bottom Line for This Patient
At 18 ng/dL, this 48-year-old woman's testosterone is in the lower-normal range for her age. Treatment is not indicated unless she has specific symptoms of androgen deficiency after excluding other causes and ensuring adequate estrogen status 1, 2. The number alone does not define deficiency—clinical context is paramount.