Menstrual Cycle

The menstrual cycle is a naturally recurring process that involves the progression of various hormonal and physiological changes in the female reproductive system each month, preparing the body for potential pregnancy. The average length of the menstrual cycle is around 28 days, however, it can range anywhere from 21 to 35 days.

While menstruation is considered a normal physiological process, understanding its complexities can empower females to take responsibility for their reproductive well-being, plan pregnancies, and promptly recognize any potential issues or irregularities. Let’s dive into the details of the menstrual cycle, its phases, hormonal changes, and common menstrual disorders.

How long is the normal menstrual cycle?

The average length of the menstrual cycle is 28 days, however, a length between 21 to 35 days is still considered normal. The menstrual cycle is counted from the first day of one menstrual period to the first day of the next.

However, it is essential to note that the menstrual cycle can differ for each woman, and there is a wide range of what can be considered normal. Factors like stress, hormonal changes, and medical conditions can impact the length and regularity of a menstrual cycle. 

How long does a menstrual period last?

The duration of a menstrual period can vary from one woman to another. On average, it can last for about 3 to 7 days. Some females may have shorter or lighter bleeding, lasting only a few days, while others may experience longer and heavier bleeding for up to 7 days.

The flow of blood can change throughout a menstrual period. It usually starts with a lighter flow, becomes heavier for a couple of days, and then decreases towards the end of the period.

How much does a woman bleed during the menstrual cycle?

The amount of blood a woman loses during her menstrual cycle can vary from one woman to another and even from one cycle to another for the same woman. While it is difficult to provide a precise estimate, a general idea can be given.

On average, women lose about 30 to 40 milliliters (around 2 to 3 tablespoons) of blood during their whole menstrual cycle each month. Blood loss during a cycle can be affected by factors such as clotting, fluid retention, and individual sensitivities.

At what age does menstruation begin?

The age at which a young girl starts menstruation is known as menarche. It commonly occurs between the age of 9 to 16 but the average age of menarche is around 12 years. However, it is important to remember that variations exist, and some girls can experience menarche earlier or later than the average age.

Several factors can influence the timing of menarche, including genetic factors, body weight, nutritional status, and overall health. Young girls often reach menarche closer to the age when their mothers or older sisters started menstruating, primarily due to genetic factors.

The onset of menstruation can be preceded by other signs of puberty, such as breast development and the growth of pubic hair. These changes typically occur before menarche.

What are the phases of the menstrual cycle?

The menstrual cycle can be divided into four main phases: the menstrual phase, the follicular phase, ovulation, and the luteal phase. Here is a brief explanation of each phase:

Menstrual phase

The menstrual phase denotes the start of the cycle and is characterized by the shedding of the uterine lining. During this phase, the levels of estrogen and progesterone (hormones responsible for menstruation) are low and the body is eliminating the unfertilized egg from the previous cycle.

Because of this, it begins the shedding of the endometrium (the inner lining of the uterus). This shedding causes bleeding, which ordinarily lasts for about 3 to 7 days. Females may experience the following symptoms during the menstrual phase:

  • Menstrual cramps
  • Mood swings
  • Bloating
  • Breast tenderness
  • Irritability and tiredness
  • Headaches and lower back pain.

Follicular phase

The follicular phase begins after the menstrual phase. The pituitary gland in the brain starts to release the follicle-stimulating hormone (FSH), which stimulates the growth of ovarian follicles. Each follicle contains an immature egg.

As the follicles grow, they produce estrogen, which causes the endometrium to thicken and prepares it for the implantation of a fertilized egg. This phase normally lasts for about 16 days.


Ovulation is the release of a mature egg from one dominant follicle from the ovary into the fallopian tube, making it available for fertilization. It happens roughly halfway through the cycle, approximately on day 14 in a 28-day cycle.

The surge of the luteinizing hormone (LH) from the pituitary gland triggers ovulation. The released egg is then available for fertilization for around 12 to 24 hours. Ovulation can be identified by the following symptoms:

  • A slight rise in basal body temperature
  • Pain in the lower abdomen called ovulation pain or mittelschmerz
  • Thick discharge.

Luteal phase

After ovulation, the ruptured follicle in the ovary changes into a structure called the corpus luteum. This structure produces progesterone, which prepares the uterus for implantation by thickening the endometrium and promoting the secretion of nutrients. If fertilization does not occur, the corpus luteum degenerates, progesterone levels drop, and the next menstrual phase starts. The luteal phase typically lasts for about 10 to 16 days.

Females may experience symptoms of premenstrual syndrome (PMS) during this phase that include:

  • Mood changes
  • Headache and body aches
  • Changes in sexual desire
  • Food cravings
  • Bloating.
MenstrualMenstrual cramps
Mood swings
Breast tenderness
Lower back pain
FollicularMay not have noticeable symptoms, but the body is preparing for potential pregnancy
OvulationSlight rise in basal body temperature
Ovulation pain (mittelschmerz)
Thick discharge
LutealSymptoms of PMS:
Mood changes
Body aches
Changes in sexual desire
Food cravings

How do different hormones affect the menstrual cycle?

The menstrual cycle is regulated by a complex interplay of hormones, primarily estrogen and progesterone. These hormones are produced by the ovaries and play important roles in preparing the body for potential pregnancy. They regulate changes in the uterine lining, the consistency of cervical mucus, and the release of eggs. Here is a brief overview of hormonal changes during the menstrual cycle:

Follicle Stimulating Hormone (FSH)

This hormone is released by the pituitary gland at the start of the menstrual cycle. It stimulates the growth of follicles in the ovaries. Each follicle contains an egg.

Luteinizing Hormone (LH)

The pituitary gland also releases LH, which triggers ovulation (release of the mature egg from the ovarian follicle). It also promotes the transformation of the ruptured follicle into the corpus luteum, which produces progesterone.

Gonadotropin-Releasing Hormone (GnRH)

This hormone is produced in the hypothalamus and signals the pituitary gland to produce and release FSH and LH.


Estrogen levels increase during the follicular phase, peaking just before ovulation, and control the thickening of the uterine lining. It additionally promotes the production of cervical mucus, which facilitates the movement of sperm through the reproductive tract.


Progesterone levels increase during the luteal phase, following ovulation. It supports the further development of the uterine lining and creates a nourishing environment for an expected embryo. It maintains the thickened uterine lining and prepares the body for pregnancy. If fertilization doesn’t occur, progesterone levels fall, and the next menstrual phase starts.

Does your menstrual cycle change with age?

The menstrual cycle can vary throughout a woman’s life as she goes through different stages of reproductive and hormonal development. Here is an overview of how the menstrual cycle can change with age:

Puberty and adolescence

Periods usually begin during puberty, which commonly occurs between the ages of 9 and 16, with an average age of around 12 years. Hormonal fluctuations are common during this phase, leading to changes in cycle length, flow, and associated symptoms. It may take some time for the menstrual cycle to regulate into a more predictable pattern.

Reproductive years (20s to 40s)

During the reproductive years, cycles commonly become more normal and predictable. In these reproductive years, women are most fertile. Each month, the body prepares for potential pregnancy by thickening the lining of the uterus.

Perimenopause and menopause (Late 40s to Mid 50s)

Perimenopause refers to the transitional stage leading up to menopause, during which the ovaries produce fewer hormones. Menstrual cycles during perimenopause can become irregular, with variations in cycle length, missed periods, and unpredictable ovulation.

Menopause is defined as the absence of a period for 12 consecutive months, marking the end of the reproductive years. Once menopause is reached, menstruation ceases, and fertility declines. The symptoms of perimenopause and menopause include:

  • Irregular periods
  • Hot flashes and night sweats
  • Sleep disturbances
  • Mood changes
  • Dry skin, dry eyes, or dry mouth
  • Changes in sexual desire
  • Hair thinning or loss
  • Vaginal dryness
  • bone loss
  • Increased urinary tract infections.


Post-menopause is defined as the years after menopause. In the post-menopause stage, the ovaries no longer release eggs and produce less estrogen and progesterone. Because of these changes in hormone levels, the menstrual cycle does not take place and women no longer get pregnant. The symptoms of post-menopause include:

  • Vaginal dryness
  • Discomfort during sex
  • Bone loss
  • Increased urinary tract infections.

Evaluate your Menstruation Hygiene

Picture showing different menstruation products

What are the signs of your period coming?

There are a few signs that can help you predict your periods. The symptoms described here are influenced by various factors and can differ from one female to another.

  • Breast tenderness: Many women experience breast tenderness or sensitivity in the days just before their periods. The breasts might feel swollen, sore, or more sensitive to touch.
  • Bloating: Many women might experience bloating or a feeling of fullness in their abdomen. This can be due to hormonal changes and water retention.
  • Mood changes: Hormonal fluctuations can also affect your mood and emotions. Some women may experience mood swings, irritability, anxiety, or feelings of sadness a few days before their menstrual cycle begins.
  • Fatigue: Some women feel more tired or more exhausted than usual as their period draws near. Hormonal changes combined with the body’s preparation for the menstrual cycle, can add to feelings of fatigue or weakness.
  • Acne breakouts: Hormonal fluctuations before the menstrual cycle can also lead to acne breakouts, especially around the chin, jawline, and different areas of the face.
  • Food cravings: It is common for females to experience food cravings, especially for sweet or salty foods, in the premenstrual phase. This is often referred to as a PMS craving.
  • Headaches and migraines: The fluctuations of estrogen and progesterone influence blood vessels and neurotransmitter levels. A decrease in estrogen results in lower serotonin levels, leading to dilation and subsequent constriction of blood vessels, which can cause menstrual headaches.
  • Stomach or lower back pain: Females might also experience mild pain or discomfort in the lower abdomen or lower back as the period approaches near. This is known as premenstrual cramping and is caused by the uterus preparing to shed its lining.

What are irregular periods?

Irregular periods are described as:

  • Menstrual cycle longer than 35 days or shorter than 21 days
  • Not getting a period for 90 days
  • Periods that last longer than 7 days
  • Heavy or prolonged bleeding during menstruation
  • Lighter menstrual flow than usual
  • Periods that are accompanied by severe pain, cramping, nausea, or vomiting
  • Complete absence or skipping of periods.

What are the common menstrual disorders?

The menstrual cycle is a complex natural process. While most women experience their periods without major complications, some might encounter specific issues that can cause distress or require medical attention. Here are a few menstrual disorders:

  • Amenorrhea: It refers to the complete absence or stoppage of periods. When a girl is over 16 years of age and has not yet experienced her first period. It is called primary amenorrhea. Secondary amenorrhea refers to the absence of periods for consecutive 3 months or more, in females who previously had regular menstruation.
  • Oligomenorrhea: It is characterized by infrequent and inconsistent periods, with a menstrual cycle longer than 35 days or having fewer than 9 periods in a year. Females with oligomenorrhea may also experience lighter menstrual bleeding than usual.
  • Polymenorrhea: It involves having more frequent periods than normal. The length of the menstrual cycle is shorter than 21 days, and periods occur with greater frequency.
  • Menorrhagia: Menorrhagia refers to prolonged and heavier flow than usual that can last longer than 7 days. It can be caused by a hormonal imbalance, uterine fibroids, polyps, or adenomyosis.
  • Metrorrhagia: It is characterized by irregular or unpredictable bleeding between menstruations. This bleeding can occur at any time during the menstrual cycle.
  • Dysmenorrhea: This is characterized by severe menstrual cramps, also known as painful periods, that occur before or during menstrual periods. Dysmenorrhea is caused by elevated levels of prostaglandins, hormone-like substances that promote uterine contractions.
  • Premenstrual syndrome (PMS): PMS includes several physical and emotional symptoms that occur in the days or weeks leading up to menstruation. The most common symptoms of PMS include bloating, breast tenderness, mood swings, irritability, fatigue, and food cravings.
  • Premenstrual dysphoric disorder (PMDD): PMDD is a severe form of PMS characterized by extreme mood changes, depression, anxiety, and other symptoms that significantly interfere with a woman’s daily life.
  • Endometriosis: Endometriosis is a medical condition in which tissue that lines the uterus (endometrium) grows outside the uterus, mostly on the ovaries, fallopian tubes, or other pelvic organs. It can cause severe pelvic pain, heavy or irregular periods, and fertility problems.
  • Polycystic ovary syndrome (PCOS): PCOS is a hormonal disorder where the ovaries produce more than normal levels of androgens (male hormones). It can lead to irregular and infrequent periods or the menstruation is completely absent. Other symptoms of PCOS include acne, excessive hair growth, weight gain, and infertility.

How do different factors affect the menstrual cycle?

There are several factors that could cause disruptions and irregularities in the menstrual cycle. These factors can differ from one woman to another. Some of these factors include:

  • Stress: High levels of stress, whether physical or emotional, can disrupt the hormonal balance and lead to menstrual abnormalities.
  • Excessive exercise: Intense and excessive physical activity, especially when combined with inadequate calorie intake, can affect hormonal balance and lead to irregular periods. This condition is known as exercise-induced amenorrhea.
  • Weight fluctuations: Significant weight loss or gain can also disturb hormonal balance and affect the menstrual cycle.
  • Medications and contraceptives: Some medications, like antidepressants or antipsychotics, can affect the menstrual cycle. In addition, certain types of contraceptives, such as hormonal birth control methods, can lead to changes in menstrual cycle patterns.
  • Age: As women approach their late 30s to mid-40s, they may experience changes in their menstrual cycle due to perimenopause.

How to track your periods?

Tracking your periods can help you understand your menstrual cycle. Period trackers predict your ovulation and next period dates. Here are some methods you can use to track your periods:

  • Tracking with Menstrual Portal: The period tracker at Menstrual Portal predicts precise ovulation, fertile window, and period dates. It is very helpful if you’re attempting to conceive, schedule your activities around your cycle, or just want to understand your body better.
  • Calendar method: Use a calendar to mark the first day of your period every month. Count the number of days between the beginning of one cycle and the beginning of the next to determine your cycle’s length. Over time, you will see a pattern. In this way, you can predict your next periods.
  • Period tracking applications: There are various menstrual cycle tracking applications available for smartphones, such as Clue, Flo, and Period Tracker. These applications allow you to log the start and end dates of your periods, track symptoms, record mood changes, and even predict future cycles.
  • Menstrual cycle tracking devices: Some wearable devices and smartwatches come with built-in menstrual cycle tracking features. These devices can monitor your menstrual cycle and can predict your ovulation and period dates. They sync with smartphone applications to give you comprehensive details about your periods.

When to seek medical advice?

It is advised to seek medical attention if you experience severe pain, heavy bleeding, irregular periods, sudden changes in menstrual patterns, severe emotional symptoms, or fertility issues. Consulting with a medical professional is crucial to diagnose and treat underlying conditions and manage menstrual cycle disorders effectively. Menstrual Portal also offers free online consultation, regarding all your menstrual health concerns.

Frequently asked question

What is considered an irregular period?

Periods that are less than 21 days or more than 35 days apart, missing three or more periods in a row, and menstrual flow that is significantly heavier or lighter than usual are considered irregular periods.

Is it normal for your period date to change every month?

The start of your period may change each month. Variations in the menstrual cycle can lead to different period dates. It is possible that you may not have your period on the same day as the last one.

What is the color of healthy period blood?

It can be bright to dark red.

What kind of discharge is there before your period?

Due to the elevated levels of progesterone, discharge before a period is often hazy or white.

Last medically reviewed on July 28, 2023.