Educational information from Her Form — reviewed for accuracy by our health specialists.
Not a substitute for personal medical advice. Optional 1:1 consults with Robyn, our consulting women's-health specialist, are available on request.
What it is
FSH is released by the pituitary to stimulate ovarian follicles. The ovaries respond with estradiol, which feeds back to keep FSH low. As reserve declines, the brain pushes FSH higher to compensate.
Why it matters for women
Day-3 FSH is a window into ovarian reserve and perimenopausal transition. Persistently high FSH (>25) plus low estradiol points to menopause; fluctuating FSH is the hallmark of perimenopause.
Optimal range
Day 3: 3–9 mIU/mL. Menopause: >30.
Standard lab range
Standard ranges go up to 12 on day 3.
When it's high
- ↑Diminished ovarian reserve
- ↑Perimenopause / menopause
- ↑Irregular cycles
When it's low
- ↓Hypothalamic suppression (under-fuelling, over-training)
- ↓PCOS pattern (often with low LH ratio reversed)
References
- Endocrine Society — Female hormone health— Sex hormone assessment and interpretation in women
- Jean Hailes for Women's Health— Comprehensive women's hormone health guidance
- RANZCOG — Women's health guidelines— ANZ clinical standards for reproductive-age women
- NICE — Women's health guidelines— Evidence-based hormone and reproductive health guidance
References are provided for educational context only. Always interpret results with a qualified healthcare professional.
A note on interpretation. Ranges above are what our health specialists works to in healthy women. They are not a diagnosis — a single result always needs context from your symptoms, cycle phase and other markers.