Follicular phase

What does follicular phase mean?

Follicular phase: From day 1 of your period until ovulation; the part of the cycle that varies most in length.

How it is used in the Splash library

• The Follicular phase varies the most in length.

  From “The four phases, in depth”

• Ovulation is estimated by counting back from your expected period, because the luteal phase is usually steadier than the Follicular phase.

  From “Why your predictions shift”

• That review (McNulty and colleagues, 2020) found performance might be very slightly lower in the early follicular phase, around your period, compared with the other phases.

  From “Exercise by phase: listen first, plan second”

• Appetite rises a little in the second half of the cycle. A 2025 review of 15 datasets found people ate more, on average, in the luteal phase than the follicular phase.

  From “Eating by phase: what the evidence really says”

• A 2020 review pooling many studies found performance might be very slightly lower in the early follicular phase (around your period) on average, but the effect was trivial, the evidence was low quality, and it varied a lot between people.

  From “Exercising on your period”

Follicular phase explained

The follicular phase is the first half of the menstrual cycle, from the first day of your period until ovulation. It is named after the follicles in the ovary, small fluid-filled sacs that each hold an immature egg.

Follicle-stimulating hormone (FSH) helps several follicles grow, and usually one becomes dominant. As it grows it makes more oestrogen, which rebuilds the womb lining. When oestrogen is high enough, it triggers the LH surge that leads to ovulation.

What's typical

The follicular phase varies more than any other part of the cycle. It can be anywhere from about 10 to over 20 days, which is why cycle lengths differ between people and from month to month (Bull, 2019).

Many people feel energy and mood lift as oestrogen rises towards ovulation, and cervical mucus becomes wetter and clearer. Stress, illness and travel can delay ovulation and make this phase longer.

When to talk to a GP, nurse or pharmacist

• Your cycles are often longer than 35 days or very unpredictable, which can mean ovulation is delayed or not happening.
• Your periods have stopped for 3 months or more and you are not pregnant (NHS).
• You have heavy or long periods that last more than 7 days.

In the UK you can call NHS 111 for advice at any time. In an emergency call 999 (UK) or 911 (US). This is general information, not medical advice.