Your Menstrual Cycle Explained: What Is Happening in Each Phase and What Your Symptoms Mean

Most women are taught one thing about their cycle: when to expect their period. What they are rarely taught is what is actually happening hormonally across the month — or what the symptoms in each phase are communicating.

Your cycle is not an inconvenience. It is a monthly diagnostic — a recurring readout of your hormonal and systemic health. When you understand what each phase should feel like, the deviations become meaningful rather than mysterious.

The Four Phases

Phase 1: Menstruation (Days 1–5)

What is happening: Oestrogen and progesterone are at their lowest — triggering the uterine lining to shed. This is the reset point of the cycle. The hypothalamus begins sending GnRH signals to initiate the next follicular phase.

What you might feel: Fatigue, cramping, lower back ache, lower mood. Some women feel a quiet clarity once bleeding begins — the tension of the premenstrual phase releases.

What symptoms are telling you:

• Severe cramps that require pain medication — prostaglandin excess, often linked to oestrogen dominance or inflammatory diet
• Very heavy bleeding (soaking through pads hourly) — high oestrogen, low progesterone, or structural issues like fibroids
• Very light or absent bleeding — low oestrogen, excessive exercise, undereating, or perimenopause
• Dark, clotty blood — stagnation, often linked to oestrogen dominance and poor circulation
• Bright red, smooth flow for 3–6 days — healthy cycle

Phase 2: Follicular Phase (Days 6–13)

What is happening: FSH from the pituitary stimulates follicle development in the ovaries. The dominant follicle produces increasing amounts of oestradiol. Cervical mucus begins to become clearer and more elastic. The uterine lining rebuilds.

What you might feel: Rising energy, improving mood, increasing social confidence and cognitive sharpness, libido beginning to stir. This is typically the most outward-facing, productive phase of the cycle.

What symptoms are telling you:

• Persistent fatigue in the follicular phase — often low iron from heavy periods, or thyroid imbalance
• Ongoing low mood even as oestrogen rises — may indicate depleted serotonin, gut issues, or nutritional deficiencies

Phase 3: Ovulation (Around Day 14)

What is happening: The LH surge triggers the release of the dominant egg. Oestradiol peaks just before ovulation. Cervical mucus is at its most fertile — clear, stretchy, egg-white consistency. Testosterone also peaks briefly, supporting libido and confidence.

What you might feel: Peak energy, libido, confidence, and social ease. Some women notice a brief sharp pain (mittelschmerz) on one side as the follicle ruptures.

What symptoms are telling you:

• Migraines around ovulation — linked to the rapid oestrogen rise and fall; common in women who also have menstrual migraines
• No identifiable ovulation signs — may indicate anovulatory cycles; worth tracking with basal body temperature

Phase 4: Luteal Phase (Days 15–28)

What is happening: The corpus luteum (formed from the ruptured follicle) produces progesterone. Progesterone rises through the first half of the luteal phase, then falls sharply in the second half if pregnancy has not occurred. This drop triggers menstruation.

What you might feel: A natural slowing — more inward, less driven, more sensitive. With healthy progesterone levels, this feels like a reflective but essentially steady phase. With low progesterone, it becomes the PMS window.

What symptoms are telling you:

• Anxiety, irritability, or rage in the week before your period — low progesterone, GABA effect absent
• Bloating and breast tenderness — oestrogen dominance relative to progesterone
• Waking at 3am in the luteal phase — progesterone decline removing sleep support
• Spotting before your period — short luteal phase, often low progesterone
• Cycle shorter than 24 days — often progesterone deficiency and shortened luteal phase

What a Healthy Cycle Looks Like

• Length: 24–35 days, consistent month to month
• Bleeding: 3–7 days, moderate flow, bright to medium red, minimal clots
• Luteal phase: at least 10–12 days after ovulation
• PMS: mild and manageable — not cycle-derailing
• Ovulation signs: detectable changes in cervical mucus and/or basal body temperature

Tracking Your Cycle

Tracking your cycle — noting cycle length, bleeding characteristics, mood, energy, sleep, and physical symptoms across phases — is one of the most useful things you can do for your hormonal health. Patterns that repeat across 2–3 cycles are meaningful and provide a practitioner with far more useful information than a single blood test.

Frequently Asked Questions

What is a normal cycle length?

A normal cycle is 24–35 days, counting from the first day of one period to the first day of the next. A cycle that was consistently 28 days but has become 24 or 22 is worth paying attention to — shortening cycles are often an early sign of perimenopause or progesterone decline.

Why do I feel so different in different weeks of my cycle?

Because you are hormonally different. Oestrogen and progesterone fluctuate significantly across the cycle, directly affecting serotonin, GABA, cortisol sensitivity, and nervous system tone. The energy and mood differences between the follicular and luteal phases are physiological — not psychological.

What does brown period blood mean?

Brown blood at the start or end of your period is old blood — typically from the previous cycle's lining being cleared slowly. Predominantly brown flow, or significant spotting before your period starts, can indicate slow uterine clearance, low progesterone, or oestrogen dominance. Worth tracking across cycles.