Before perimenopause, most women’s cycles follow a relatively predictable 28-day pattern. Here is what your hormones are doing behind the scenes and why it matters when things start to change.
Day 1–5: Your Period Begins
- This is the menstrual phase, when your uterine lining sheds.
- Both estrogen and progesterone are at their lowest levels.
- You may feel tired, withdrawn, or crampy because your body is starting over.
Day 6–11: Follicular Phase (Rebuild and Rise)
- Estrogen begins to rise, helping rebuild the uterine lining.
- Progesterone remains low during this time.
- Energy, mood, and skin often improve thanks to estrogen's support of serotonin and collagen.
Day 12: Estrogen Surges
- Estrogen peaks to trigger ovulation.
- This surge helps release an egg and also supports brain, bone, and mood health.
- You may feel more social, energetic, and confident during this time.
Day 14: Ovulation
- The mature egg is released from the ovary.
- The corpus luteum forms and begins producing progesterone.
- This phase prepares your body for a possible pregnancy.
Day 14–20: Luteal Phase (The Progesterone Phase)
- Progesterone levels steadily increase, helping to calm the nervous system, improve sleep, and thicken the uterine lining.
- Estrogen levels stabilize but do not continue rising.
- This is typically when hormones feel the most balanced if ovulation has occurred.
Day 21: Progesterone Peaks
- Progesterone reaches its highest level.
- If pregnancy has not occurred, the body prepares to shed the uterine lining.
- You may feel slightly tired or introspective.
Day 21–28: Hormone Drop and PMS
- Both progesterone and estrogen begin to decline.
- This drop often triggers PMS symptoms such as mood swings, cravings, bloating, or poor sleep.
- Once hormone levels are low enough, the body signals the uterus to begin the next period.
Back to Day 1
This monthly pattern is why perimenopause can feel so destabilizing. As ovulation becomes irregular, progesterone may not be produced at all, and estrogen levels can spike or crash unpredictably. This hormonal instability is what causes so many of the symptoms women experience in their 40s.