Learn about the 4 phases of the menstrual cycle, including menstruation, follicular, ovulation, and luteal phases, hormones, symptoms, and when to see a doctor.
Dr. Kamran
Understanding the 4 phases of the menstrual cycle matters because every symptom you notice across the month, from energy shifts to cramps to mood changes, ties back to predictable hormonal patterns. When you know what your body is doing and why, it becomes easier to tell a normal fluctuation from a sign worth discussing with a doctor.
The menstrual cycle is the monthly series of hormonal changes that prepare the uterus for a possible pregnancy. It starts on the first day of your period and ends the day before your next period begins.
A 28-day cycle is often used as a reference, but cycle length varies between individuals and can vary from cycle to cycle. In adults, cycles occurring approximately every 21 to 35 days are generally considered within the normal range. The length can also shift slightly from month to month in the same person. What matters most is a pattern that feels consistent for you.
The cycle is controlled by a conversation between the brain (specifically the hypothalamus and pituitary gland) and the ovaries, mediated by four key hormones: follicle-stimulating hormone (FSH), luteinising hormone (LH), oestrogen, and progesterone.
The menstrual phase begins on Day 1 of menstrual bleeding and commonly lasts about 3 to 7 days, although the duration can vary between individuals.
What triggers it: progesterone and oestrogen levels fall sharply at the end of the previous cycle. Without those hormones sustaining it, the thickened uterine lining (endometrium) breaks down and is shed through the cervix as menstrual blood and tissue.
Bleeding that requires changing a pad or tampon every hour for several hours in a row, bleeding that lasts more than 7 days, or bleeding that interferes with daily activities may indicate heavy menstrual bleeding and should be discussed with a healthcare professional.
The follicular phase begins on Day 1 of the menstrual cycle and continues until ovulation. It overlaps with the menstrual phase at the beginning of the cycle. In a 28-day cycle, ovulation often occurs around the middle of the cycle, but the timing can vary considerably between individuals and from cycle to cycle.
During this phase, the pituitary gland releases FSH, which signals several follicles in the ovaries to begin maturing. Each follicle contains an egg. As they develop, they produce oestrogen, which does two important things: it thickens the uterine lining again (rebuilding what was shed) and eventually triggers the LH surge that leads to ovulation.
Usually, one follicle outpaces the others and becomes dominant. The rest are reabsorbed.
Hormonal changes during the follicular phase may coincide with changes in mood, energy, appetite, or other symptoms, but these experiences vary widely between individuals. There is not a predictable set of mood, skin, concentration, or sleep changes that everyone experiences during this phase.
Ovulation is a brief event in which an ovary releases an egg. The egg remains viable for roughly 12 to 24 hours after ovulation, while the fertile window is wider because sperm can remain viable in the female reproductive tract for several days.
When oestrogen peaks, the pituitary releases a sudden surge of LH. This surge triggers the dominant follicle to rupture and release its egg into the fallopian tube. Ovulation does not necessarily occur on Day 14. It generally occurs about 14 days before the next menstrual period, although the timing varies. Therefore, someone with a longer cycle may ovulate later than someone with a shorter cycle.
After ovulation, the released egg is generally capable of being fertilised for about 12 to 24 hours. Sperm can remain viable in the female reproductive tract for up to about 5 days under favourable conditions. Because the egg remains viable for only about 12 to 24 hours after ovulation, the fertile window generally includes the several days leading up to ovulation and approximately the day of ovulation.
After ovulation, the ruptured follicle transforms into a temporary gland called the corpus luteum. This gland releases progesterone, and oestrogen levels rise again to a secondary, lower peak. This combined hormonal environment supports the uterine lining in case a fertilised egg implants.
The luteal phase begins after ovulation and generally lasts around 12 to 14 days, although some variation occurs between individuals and cycles. Compared with the follicular phase, its length tends to vary less.
If pregnancy does not occur, the corpus luteum eventually regresses, causing progesterone and oestrogen levels to fall. This hormonal decline contributes to breakdown and shedding of the uterine lining, leading to the next menstrual period. Progesterone and oestrogen drop, the uterine lining loses its support, and the menstrual phase begins again.
PMS symptoms typically occur during the luteal phase and improve after menstruation begins. Although changes in ovarian hormones are involved, the exact biological mechanisms underlying PMS are complex and are not explained simply by a drop in progesterone alone.These luteal phase symptoms can include:
When these symptoms are severe enough to interfere with daily life and relationships, the pattern may be premenstrual dysphoric disorder (PMDD), which warrants evaluation by a gynaecologist.
Most variation in cycle length, flow, and minor discomfort falls within normal range. The following, however, are worth a medical review:
Irregular periods causes are wide-ranging. Possible causes include pregnancy, thyroid disorders, polycystic ovary syndrome (PCOS), significant changes in weight, excessive exercise, stress, certain medications, and the hormonal changes associated with perimenopause. A few missed or shifted periods during a stressful life event are usually not alarming, but a persistent pattern deserves investigation.
Report adverse events to your healthcare provider or the relevant regulatory authority.
Some people use tools or products to track their cycle or manage symptoms, including hormonal contraceptives, cycle-tracking apps, or over-the-counter pain relief. A few important points:
If you are unsure which symptom-relief approach is right for you, speak to a gynaecologist before starting any regimen.
Understanding the four phases of the menstrual cycle—the menstrual, follicular, ovulatory, and luteal phases—can help you recognise how hormonal changes may influence bleeding, fertility, and symptoms throughout the cycle. However, cycle length, ovulation timing, bleeding patterns, and symptoms vary from person to person, so there is no single pattern that applies to everyone. Tracking your periods and any recurring symptoms can help you understand your own pattern and identify meaningful changes. If your cycles become persistently irregular, bleeding is unusually heavy, or pain or other symptoms interfere with daily life, consult a qualified healthcare professional for appropriate evaluation.
The four phases are the menstrual phase, the follicular phase, the ovulation phase, and the luteal phase. Together they make up one complete cycle, driven by coordinated changes in FSH, LH, oestrogen, and progesterone.
The duration of each phase varies. Menstrual bleeding commonly lasts about 3 to 7 days. The follicular phase begins on Day 1 and continues until ovulation, so its length can vary considerably. Ovulation is a brief event rather than a phase lasting a fixed number of days, and the egg can generally be fertilised for about 12 to 24 hours after release. The luteal phase follows ovulation and commonly lasts around 12 to 14 days.
Four hormones work together: FSH stimulates the development of ovarian follicles, while LH helps trigger ovulation and supports formation of the corpus luteum. Oestrogen produced during follicular development helps the uterine lining grow, and progesterone produced after ovulation helps maintain the uterine lining and prepare it for possible implantation.
Yes, some variation of a few days from cycle to cycle is common and not a cause for concern. Stress, illness, travel, and changes in weight or exercise can all shift cycle length temporarily.
Menstrual cycles may be considered irregular when they consistently fall outside the expected range for age, when the interval between periods varies substantially, or when previously predictable cycles become noticeably irregular. Missing several periods without pregnancy also warrants medical evaluation. A healthcare professional can assess the pattern and determine whether an underlying cause needs investigation.
