Hormones & blood testsDraft: awaiting clinical review

Oestrogen (oestradiol)

The main hormone produced by developing follicles, preparing the womb lining for a possible pregnancy.

Overview

Oestradiol is the main form of oestrogen in the reproductive years. It rises during the first half of the cycle as a follicle grows, peaks just before ovulation, and helps thicken the womb lining.

It is sometimes measured in the early part of the cycle (days 2–5) together with FSH.

What is well established

Oestradiol levels change considerably across the cycle, so results must be interpreted alongside the cycle day.
A high oestradiol level early in the cycle can lower FSH and make an FSH result look more reassuring than it is.

Uncertain or emerging evidence

'Oestrogen dominance', as described in some online sources, is not a recognised medical diagnosis, and evidence for tests or treatments marketed for it is lacking.

This guide is general information and does not replace advice about your own circumstances. Clinical review pending.