Understanding the Follicular Phase: What Happens and Why It Matters


Our menstrual cycle lasts for 21-35 days. The standard is 28 days. It is divided into four phases, menstruation, follicular, ovulation, and luteal.

The second phase of the menstrual cycle is the follicular phase. The start of this section overlaps with menstruation as it also begins from Day 1 of the cycle. Follicular phase takes place in the ovary.

This phase can last from 10-21 days. It varies with every cycle. However, the usual duration is 13-16 days. It is the longest phase in the cycle.

Duration: 10-21 days.

Average: 14 days


  • Follicular Stimulating Hormone (FSH) ↑
  • Estrogen ↑


  • Increased energy
  • Better concentration

What Happens in the Follicular Stage?

Your brain has a section called Hypothalamus. It is the connecting force between your endocrine system (hormone system) and the nerves.

Hypothalamus signals the pituitary gland to release Follicular Stimulating Hormone (FSH). Just as the name suggests, this hormone ‘stimulates’ or triggers your ovaries to mature the follicles.

Follicles are small sacs filled with fluid and they contain immature eggs. These eggs are unfertilized.

Did you know women are born with all their eggs and ovarian follicles? They remain latent until you start puberty and then start developing. Only one-fourth of the follicles remain once you start puberty. They decrease over time.

Only one ovary will release follicles, usually 5-20 in quantity. The follicle with the healthiest egg will become the dominant one and only this egg will mature. The other follicles will decay and be absorbed into the ovary. This usually happens on Days 10-13.

The process of follicle maturing triggers a rise in estrogen. This hormone starts thickening the endometrium (inner uterus wall) for pregnancy preparation.

The next phase is ovulation. It begins after the mature egg finally bursts out of the follicle.

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