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Demystifying the Menstrual Cycle (Period): Phases and Menstruation Explained



The menstrual cycle is a vital aspect of every woman's life. This cyclical process involves distinct phases, each with its unique hormonal orchestration. By the end of this blog, you will not only learn the natural biological process behind this phenomenon but also gain a profound knowledge of a woman's reproductive health. From the menstrual phase, where the uterine lining sheds, to the ovulatory phase, you will understand the rhythmic change of hormone levels in a woman's body as she experiences menstruation. Stay with this guide to know more!

What is Menstruation?

Menstruation is a natural and vital physiological process in the reproductive cycle of women, typically occurring every month. It is a biological mechanism that prepares and maintains the female reproductive system for pregnancy. The phase is also known as the menses phase, menstrual phase, or menstrual cycle in biology. Commonly known as a period, this process involves the shedding of the uterine lining.

Periods are regulated by a complex interplay of hormones, particularly Estrogen and Progesterone. The menstrual cycle involves a series of hormonal fluctuations orchestrated by the ovaries and pituitary gland to prepare a woman's body for pregnancy. However, in the absence of pregnancy, the uterine lining thickens during the menstrual cycle to create a nurturing environment for a potential fertilised egg. If fertilisation does not occur, hormonal signals in the woman's body prompt the shedding of this built-up uterine lining. This shedding is what we observe as menstrual bleeding.

What is a Menstrual Cycle?

The menstrual cycle is a recurring, approximately 28-day physiological process in women, produced by hormonal fluctuations. It is divided into four phases—menstrual, follicular, ovulation, and luteal. Ovulation is an essential phase in the menstrual cycle. It occurs when a matured egg is released from the ovary and is available for fertilisation by sperm. If fertilisation does not happen, the menstrual phase restarts again next month.

How Long is a Normal Menstrual Cycle?

A normal menstrual cycle typically lasts around 28 days. However, sometimes, women can also get their periods before or after a few days of the due date in their cycle.

How Many Days Between Periods is Normal?

The normal range for the number of days between periods is typically 21 to 35 days. However, individual variations exist, and factors like stress, hormonal changes, or health conditions can influence period cycle length.

How Long Does a Normal Period Last?

A normal period lasts about 3 to 7 days.

Is a Three-Day Period Normal?

Yes, a three-day period falls within the normal range for menstrual duration. Menstrual cycle length durations can vary, and a three-day period is considered normal as long as it is part of a woman's regular period pattern.

What are the Four Phases of the Menstrual Cycle?

The menstrual cycle consists of four phases, each orchestrated by complex hormonal interactions and physiological changes. Below is an overview of each menstrual cycle phase:

  1. Menstrual Phase (Days 1-5)

The menstrual or menses phase marks the beginning of a woman's menstrual cycle and lasts about 3 to 7 days. It starts on the first day of the period when the uterine lining sheds in the absence of pregnancy.

Hormonal Changes: Estrogen and progesterone levels are low at the beginning, triggering the release of the uterine lining.

  1. Follicular Phase (Days 1-13)

This phase overlaps with the menstrual phase and extends to ovulation. The ovaries produce Follicle-Stimulating Hormone (FSH), stimulating the maturation of an egg within an ovarian follicle.

Hormonal Changes: Estrogen levels rise, encouraging the thickening of the uterine lining in preparation for a potential pregnancy.

  1. Ovulatory Phase (Days 14-15)

Ovulation is a critical event in the menstrual cycle, occurring around the midpoint. A matured egg is released from the ovary and travels to the fallopian tube, awaiting fertilisation by sperm. Ovulation represents the peak of a woman's fertility.

Hormonal Changes: A surge in Luteinizing Hormone (LH) triggers ovulation. Here, estrogen levels peak and progesterone starts to rise.

  1. Luteal Phase (Days 15-28)

Following ovulation, the ruptured follicle transforms into a structure called the corpus luteum, which produces progesterone. This phase prepares the uterus for a potential pregnancy.

Hormonal Changes: Progesterone levels increase, maintaining the uterine lining. If fertilisation does not occur, the corpus luteum degenerates, leading to a decline in hormone levels and the start of a new cycle of periods.

All the four phases collectively regulate the menstrual cycle. The length of the menstrual cycle days for each of the 4 phases is different for every woman. This further leads to varying menstrual cycle patterns among them.

At What Age Does Menstruation Typically Begin?

The start of periods, or menarche, typically begins in females between the ages of 9 and 16, with an average age of around 12. Girls often experience physical and hormonal changes before menarche, such as breast development and pubic hair growth. Early or late onset does not necessarily indicate a problem, but significant deviations (periods starting at an age of less than 10 years or more than 15 years) can be concerning. The initiation of periods signals the onset of reproductive maturity and the beginning of a woman's menstrual cycle.

What are the Symptoms of Getting Your Period?

Common symptoms observed during periods include:

  • Abdominal cramps
  • Breast tenderness
  • Irritability
  • Bloating
  • Fatigue
  • Some may experience headaches or acne
  • Hormonal fluctuations during menstruation contribute to mood shifts

These symptoms typically occur in women in the days leading up to periods and may vary in intensity. 

How Does Your Period Change Over Time?

A woman's menstrual cycle can undergo various changes over time due to factors like age and hormonal changes.

  • In adolescence, periods often start irregularly and may take time to establish a consistent pattern.
  • In the late teens and early twenties, period cycles in women tend to stabilise. Pregnancy and childbirth can lead to temporary changes, with irregularities in periods common during breastfeeding.
  • As women approach their late 30s and 40s, perimenopause begins, causing irregular period cycles, changes in flow, and potential symptoms like hot flashes.
  • Menopause, typically occurring in the late 40s or early 50s, marks the end of menstruation.

These changes reflect the dynamic nature of reproductive health and are influenced by lifestyle and medical conditions.

What is Considered an Irregular Period?

An irregular period is characterised by variations in the menstrual cycle length, either in terms of the number of days between periods or changes in the duration and flow of periods. While some irregularities can be normal, such as during adolescence or perimenopause, persistent irregularities in periods may indicate underlying issues. Menstrual cycles outside the typical range of 21 to 35 days or significant changes in flow, accompanied by severe pain, may be considered irregular.

How Much Should I Bleed During My Period?

The amount of period blood varies among women, but a typical range lies between 30 and 40 millilitres (about 2 to 3 tablespoons) over the entire menstrual period.

It is common to experience variations in period flow throughout the cycle, with heavier flow during the first few days. While it is normal to have a range of flow, excessively heavy (Menorhaggia) or light (Hypomenorrhea) period bleeding may indicate hormonal imbalances. It can also signal uterine issues like adenomyosis, uterine fibroids or other health concerns like PCOS and thyroid disorders.

How Do I Track My Period?

Tracking your period can help you understand your menstrual cycle, identify patterns, and predict your next period. Here is a step-by-step guide on how to track your period:

  • Start a Calendar or Use a Period Tracking App: Record the start and end dates of your periods on a calendar or use a dedicated period tracking app. Many apps also allow you to log symptoms, mood changes, and other relevant information.
  • Note Flow Intensity: Track the period flow intensity each day. Note whether it is light, moderate, or heavy. This information can be valuable for identifying changes or irregularities in your cycle.
  • Monitor Symptoms: Record any symptoms you experience, such as cramps, mood swings, breast tenderness, or headaches. Over time, this can help you anticipate and manage premenstrual symptoms.
  • Calculate Cycle Length: Determine the length of your period cycle by counting the days between the first day of one period to the first day of the next. The average menstrual cycle is around 28 days, but normal variations can range from 21 to 35 days.
  • Consider Ovulation Tracking: If interested in fertility or contraception, consider tracking ovulation using methods like basal body temperature charting or ovulation predictor kits. Ovulation typically occurs around the middle of the period cycle.

When Should I Worry About My Period?

While occasional variations in periods are normal, sure signs may indicate a need for concern:

  • If your periods are consistently irregular, with unpredictable timing or significant changes in flow.
  • Severe period cramps that interfere with daily activities may suggest underlying issues such as endometriosis or fibroids.
  • Abnormally heavy period bleeding may be a sign of hormonal imbalances, uterine fibroids, or other conditions requiring attention.
  • Amenorrhea, the absence of periods, can be due to factors like pregnancy, hormonal imbalances, or issues with reproductive organs.
  • If you experience abrupt changes in your menstrual cycle or encounter irregular bleeding between periods
  • Unexplained pain during intercourse or persistent pelvic pain may be indicative of gynaecological issues. 


Whether tracking for fertility, predicting periods, or identifying irregularities, this blog provides all the information women need to manage their periods. Understanding and monitoring the menstrual cycle is essential for the overall reproductive health of a woman. Any persistent concerns or significant changes in the menstrual cycle warrant consultation with a gynaecologist for personalised guidance. Worried about underlying medical conditions that are causing irregular periods? Get yourself diagnosed at Metropolis Healthcare. Trusted by the leading doctors in India, Metropolis Healthcare provides at-home blood tests at affordable prices and generates highly accurate reports, thanks to state-of-the-art lab facilities and a vastly experienced team of phlebotomists. Book your test today!

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