The menstrual cycle is one of the body's most elegant rhythms — a monthly interplay of hormones that prepares the body for a possible pregnancy. Yet many people never learn how it actually works. Understanding the four phases, and the hormones driving each, can help you make sense of the physical and emotional shifts you notice across the month.
Key Takeaways
- The cycle has four phases: menstrual, follicular, ovulation, and luteal.
- Estrogen and progesterone rise and fall in a coordinated pattern that drives each phase.
- A "typical" cycle is about 28 days, but anywhere from roughly 21 to 35 days can be normal.
- Tracking your cycle can help you understand your body and spot changes worth discussing with a doctor.
The Basics
A menstrual cycle is counted from the first day of one period to the first day of the next. While 28 days is often cited as "average," normal cycles range widely, and some variation month to month is common.[1] The whole process is orchestrated by hormones from the brain (the pituitary gland) and the ovaries, chiefly estrogen and progesterone. For the bigger hormonal picture, see hormonal balance after 35.
1. Menstrual Phase (roughly days 1–5)
The cycle begins with your period. If pregnancy didn't occur in the previous cycle, hormone levels drop and the uterine lining (endometrium) sheds, producing menstrual bleeding. Estrogen and progesterone are at their lowest, which is why energy can feel lower for some. Bleeding typically lasts around 3–7 days.
2. Follicular Phase (roughly days 1–13)
Overlapping with menstruation and continuing after it, the follicular phase is when the pituitary releases follicle-stimulating hormone (FSH), prompting follicles in the ovary to mature. As a follicle develops, estrogen rises, rebuilding the uterine lining and often bringing rising energy and mood as the phase progresses.
3. Ovulation (around day 14 in a 28-day cycle)
A surge in luteinizing hormone (LH) triggers ovulation — the release of a mature egg from the ovary. This is the most fertile window of the cycle. Some people notice a slight rise in body temperature, changes in cervical mucus, or mild one-sided twinges around ovulation. The egg is viable for about a day, though sperm can survive several days, which widens the fertile window. For more on conception timing, see fertility after 30.
4. Luteal Phase (roughly days 15–28)
After ovulation, the empty follicle becomes a structure called the corpus luteum, which produces progesterone to maintain the uterine lining in case of pregnancy. If the egg isn't fertilized, the corpus luteum breaks down, progesterone and estrogen fall, and the cycle begins again with a period. This hormonal drop in the late luteal phase is when many people experience premenstrual symptoms — and can also affect skin, as covered in hormonal acne in women.
Why this is worth knowing: The shifts in energy, mood, appetite, and skin you may notice across the month aren't random — they track predictable hormonal changes. Understanding your pattern can make those changes feel less mysterious and more manageable.
Tracking Your Cycle
Keeping a simple record — of period dates, symptoms, and how you feel — can help you learn your personal pattern, anticipate changes, and identify what's normal for you. It's also useful information to share with a healthcare provider if questions come up.
When to See a Doctor
See a healthcare professional if your cycles are very irregular, extremely heavy or painful, suddenly change, or stop unexpectedly, or if you have bleeding between periods. These can have manageable causes worth evaluating — and getting answers is always reasonable.
References
- Mihm, M., Gangooly, S., & Muttukrishna, S. (2011). The normal menstrual cycle in women. Animal Reproduction Science, 124(3–4), 229–236. doi.org/10.1016/j.anireprosci.2010.08.030
- American College of Obstetricians and Gynecologists. (2022). The Menstrual Cycle. acog.org/womens-health/faqs/the-menstrual-cycle