The four phases of your menstrual cycle
Your menstrual cycle starts on the first day of your period and ends the day before your next one. Doctors usually split it into four phases. The names are clinical, but the idea is simple: two hormones from the brain tell the ovaries what to do, and the ovaries answer with estrogen and progesterone. Those two hormones shape the lining of the uterus, and they can also touch how you feel day to day.
The day counts below are based on a 28-day cycle because that's the textbook example. Plenty of healthy cycles are shorter or longer, so treat the numbers as a rough map and your own body as the real one.
Menstrual phase (your period)
Day one is the first day of real bleeding, not spotting. If no pregnancy happened in the last cycle, estrogen and progesterone have both dropped, and that drop tells the uterus to shed its lining. Bleeding usually lasts three to seven days and tends to be heaviest in the first two.
With hormones at their lowest, many people feel tired or want to stay in. Cramps come from prostaglandins, chemicals that make the uterine muscle contract. Some people sleep more deeply now, while others sleep worse because of pain or night sweats. Low iron from blood loss can add to fatigue if your periods are heavy.
Follicular phase
The follicular phase actually overlaps with your period. It starts on day one and runs until ovulation. The pituitary gland releases follicle-stimulating hormone (FSH), which prompts several follicles in the ovaries to grow. Each follicle holds an immature egg. Usually one pulls ahead and the rest fade back.
That growing follicle makes estrogen, and estrogen climbs steadily through this phase. It rebuilds the uterine lining and changes your cervical fluid from dry or sticky toward wetter and clearer.
A lot of people notice their energy and mood lift as estrogen rises. Workouts may feel easier, and some find they're more social or focused. Appetite is often a little lower than in the second half of the cycle. This is also the phase that changes length the most from cycle to cycle, which is why your period can arrive earlier or later than you expected.
Ovulation
When estrogen peaks, the brain responds with a sharp surge of luteinizing hormone (LH). About a day or so after the surge begins, the mature follicle releases its egg. In a 28-day cycle this happens around day 14, but the real date depends on how long your follicular phase ran.
The egg survives for roughly 12 to 24 hours. Sperm can live in fertile cervical fluid for up to about five days, so the fertile window covers the few days before ovulation plus the day itself. Cervical fluid is usually at its most slippery and stretchy right around now.
Some people feel a one-sided twinge or ache low in the belly, called mittelschmerz. Others notice a higher sex drive, slightly tender breasts or nothing at all. All of those are normal.
Luteal phase
After the egg is released, the empty follicle turns into the corpus luteum, a small temporary gland that makes progesterone along with some estrogen. Progesterone keeps the uterine lining thick and ready in case an egg is fertilized. It also nudges your resting body temperature up a little, which is the shift people track with basal body temperature charts.
If no pregnancy happens, the corpus luteum breaks down after about two weeks. Progesterone and estrogen fall, and the next period begins. If a pregnancy does start, the embryo sends a hormone signal (hCG) that keeps progesterone high.
This is the phase many people associate with premenstrual symptoms. Progesterone has a calming, slightly sedating effect, so some feel sleepier early on. Later, as hormones drop, sleep can get lighter and more broken. Appetite often goes up, and cravings for carbohydrates or sweets are common. Bloating, breast tenderness, irritability, low mood and acne flare-ups can all show up in the days before a period. For most people these symptoms are mild and ease once bleeding starts.
When premenstrual symptoms are severe enough to get in the way of work, relationships or daily life, that's worth raising with a doctor. Premenstrual dysphoric disorder (PMDD) is a recognized condition, and there are treatments that help.
Everyone's pattern is different
The mood, energy, sleep and appetite changes above are tendencies that show up in studies and in many people's experience. They are not rules. Some people feel strong shifts every month, some feel almost none, and many land somewhere in between. Stress, illness, travel, sleep, medications and hormonal birth control can all change the picture. Hormonal contraceptives in particular usually stop ovulation, so the natural rise and fall described here doesn't happen in the same way.
The most useful thing you can do is watch your own pattern for a few months. Jot down when your period starts, how you're sleeping, your energy and your mood. Over time you may see that your hungry days or low days line up with a certain part of your cycle, which can make them easier to plan around. Barkat's cycle tab lets you log these notes on your phone, and they stay private on your device.
This article is general information and not medical advice.
Sources
- Cleveland Clinic: Menstrual Cycle (Normal Menstruation)
- NHS: Periods
- NIH StatPearls: Physiology, Menstrual Cycle
- ACOG: Premenstrual Syndrome (PMS)
This is general information, not medical advice. If something about your cycle worries you, talk to a doctor or midwife.