Estradiol (E2)

Low levels are associated with reduced bone density, mood disturbances, vasomotor symptoms (e.g. hot flashes), and impaired fertility.

Elevated levels may indicate hormonal imbalance, increased aromatase activity, or oestrogen-producing pathology. Monitoring supports assessment of reproductive function, menopausal status, and hormone therapy.

At baseline / for screening: Once every 12 months from age 35, with cycle phase noted in premenopausal women (typically drawn on day 2 to 5 of a 28-day cycle for baseline). More frequently during perimenopause.

When monitoring an intervention or change: Retest 6 to 12 weeks after starting or adjusting hormone therapy (HRT, oral contraceptives, fertility medication). Cycle phase matters as much as cadence, so match the cycle day across draws for meaningful comparison. In perimenopause, expect significant cycle-to-cycle variability that settles only after menopause is established.

Note: In premenopausal women, estradiol changes 10-fold across the cycle. Always note cycle day with each draw; for trend tracking across cycles, match cycle phase (e.g., day 3 vs day 3) with at least one full cycle between draws, or use postmenopausal baselines for stable comparisons.