The Menstrual Cycle and Its Four Phases: A Simple Guide to Understanding Your Body
Medically reviewed by Zeinab Alkashaf · July 15, 2026
Quick answer
The menstrual cycle moves through four phases: menstrual (bleeding), follicular (an egg matures), ovulatory (the egg is released), and luteal (after ovulation). The average cycle is about 28 days, but 21 to 35 days is normal. These phases are driven by estrogen, progesterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH), whose shifts help explain changes in energy and mood across the month.
What is the menstrual cycle?
The menstrual cycle is a series of natural changes your body goes through each month in preparation for a possible pregnancy. It begins on the first day of menstrual bleeding and ends the day before the next period starts.
Cycle length is counted from the first day of one period to the first day of the next. The common average is about 28 days, but any length between 21 and 35 days is considered normal and varies from woman to woman.
The four phases of the menstrual cycle
The cycle is divided into four sequential phases whose edges overlap slightly and which are guided by hormones. Here is what happens in each phase, put simply:
Menstrual phase (roughly days 1–5): The uterine lining sheds as menstrual blood because no pregnancy occurred. Estrogen and progesterone are low, and you may feel lower in energy.
Follicular phase (roughly days 1–13, overlapping with menstruation): Follicle-stimulating hormone (FSH) prompts several follicles in the ovary to mature, and estrogen gradually rises, rebuilding the uterine lining. Energy and mood often improve.
Ovulatory phase (around day 14 in a 28-day cycle): Luteinizing hormone (LH) surges sharply, and the ovary releases a mature egg. This is the most fertile time of the cycle.
Luteal phase (roughly days 15–28): The corpus luteum releases progesterone to prepare the uterine lining for pregnancy. If no pregnancy occurs, hormones fall and a new cycle begins.
The key hormones in plain terms
Four main hormones run the cycle, each playing a role at a specific time. Understanding what they do helps you make sense of how you feel across the month.
Estrogen: Rises in the first half of the cycle, builds the uterine lining, and is often linked to improved energy and mood near ovulation.
Follicle-stimulating hormone (FSH): Prompts the ovary to mature follicles at the start of the cycle.
Luteinizing hormone (LH): Its sudden surge is the signal that releases the egg (ovulation).
Progesterone: Rises after ovulation to prepare the uterus for pregnancy; its drop before menstruation can accompany premenstrual symptoms.
How energy and mood shift through the month
Because hormones rise and fall across the cycle, it is normal to notice changes in your energy, focus, and mood. Many women feel more energetic near ovulation, when estrogen is high.
In the luteal phase before menstruation, premenstrual symptoms such as mood swings, bloating, or fatigue may appear. These changes are common and vary in intensity; but if they are severe enough to disrupt your daily life, it is worth talking to a doctor.
What is normal, and when is it irregular?
There is no single "perfect" cycle that fits everyone. It is normal for cycle length to range from 21 to 35 days, and for menstrual bleeding to last roughly two to seven days, with some variation from month to month.
Cycles consistently shorter than 21 days or longer than 35 days.
Missing periods for three months or more without pregnancy.
Very heavy bleeding that soaks a pad or tampon every one to two hours.
Bleeding between periods or after intercourse.
Severe pain that is not relieved by usual pain relievers.
When to see a doctor
See your doctor if you notice any of the signs above, if your cycle pattern changes suddenly, or if symptoms affect your daily life. These changes do not necessarily mean something serious, but a medical evaluation helps identify the cause and reassure you.
Frequently asked questions
How long is a normal menstrual cycle?
The common average is about 28 days, but any cycle between 21 and 35 days is considered normal. What matters is that your own pattern stays relatively consistent from month to month.
When does ovulation happen?
In a 28-day cycle, ovulation usually occurs around day 14, but the timing varies with your cycle length. It typically happens about two weeks before the next period begins.
Is it normal for my mood to change during the cycle?
Yes, shifts in energy and mood are common due to changing hormone levels, especially before menstruation. If they are severe enough to disrupt your daily life, talk to your doctor.
When is an irregular cycle a reason for concern?
See a doctor if your cycles are consistently shorter than 21 days or longer than 35 days, are absent for three months without pregnancy, or come with very heavy bleeding or severe pain.
Dawrat Hayat