Understanding What's Normal, What's Not In A Menstrual Cycle

Written by Dr. Pramod Mane on Tue, 01 August 2023

Key Highlights

  • Menstrual irregularities impact a large percentage of women around the world, and the types of irregularities vary based on several factors.
  • Everything in a menstrual cycle that worries a woman isn't an irregularity, and it's necessary to track the details to understand if there's a consistent variation from regularity, month to month.
  • When the pattern of periods shows a repeated deviation from the range of normalcy, it's essential to get medical advice to detect any infections or cysts, or tumors.
  • PCOS is a common problem in the female reproductive system and its presence may be indicated by abnormal menstrual flow or duration.
  • Some menstruation-related problems, like PMS, can't be cured, but they can be better managed through lifestyle changes once they're identified.

Nan has recently begun to worry a lot because she has noticed some abnormal symptoms of menstruation. She has been experiencing untimely periods, white discharge, faint spotting, and also severe pain during her periods.

To find out if this was something serious, Nan visited her doctor and asked her to explain why women had to suffer and go through this every month, and also understand more on the difference between what a normal menstrual cycle looks like, and an irregular menstrual cycle, and the causes for an irregular menstrual cycle.

After being told about all the period symptoms, Nan's doctor asked her to relax and not get worried. She began to explain the menstrual cycle in simple terms to Nan so that she'd understand what exactly happens and why.

Understanding the menstrual cycle

Menstrual bleeding is a time of discomfort for women, but it's part of the natural reproductive cycle. The whole process is governed mainly by the menstrual cycle hormones estrogen and progesterone. Major roles are also played by the follicle-stimulating hormone (FSH), which controls the follicular phase of the menstrual cycle and luteinizing hormone (LH), which acts upon the ovaries.

Every time a woman begins her menstrual bleeding, that's the start of a new menstrual cycle. The purpose of the bleeding is to flush out the unused inner lining of the uterus, which had thickened in the previous cycle in preparation for pregnancy. Once this flushing out is done, the uterus can prime itself for the next round of egg release.

In the previous menstrual cycle, an egg had been released from either of the two ovaries, and it waited in the corresponding fallopian tube (connecting that ovary to the uterus) to be fertilized by sperm. No sperm means no pregnancy, and no pregnancy means the start of periods. The extremely tiny egg disintegrates about 24 hours after being released if it remains unfertilized.

How long does a normal period last?

  • Each normal period lasts 3-7 days, occasionally about 2 days. Anything shorter or longer than this is considered irregular periods. The median gap between the two periods is 28 days, with the egg release happening at the mid-point, i.e. 14 days after the last period and 14 days before the next one.
  • However, few women in the world get their periods exactly once in 4 weeks all the time; for most women, the gap shrinks or stretches โ€” anything between 21 days and 35 days is considered normal โ€” all through their reproductive years. For someone like Nan, one period coming just 3 weeks after the last one might be worrying, but it's still a normal period.

The total volume of blood lost during a normal period is 30-80ml, but irregular periods would see either very scant bleeding or excessively heavy bleeding.

What are the four phases of each period cycle?

There are 4 phases of each menstrual cycle:

  • The menstrual phase (the bleeding);
  • The follicular phase (when an egg is being prepared for release);
  • The ovulatory phase or ovulation phase (when an egg has been released and awaits sperm);
  • The luteal phase (the last stage that leads to the shedding of the uterine lining in case the egg doesn't get fertilized and there's no fetus to the house in the uterus).

Some period facts worth noting include:

  • About 25% of women around the world get irregular periods, which could be either shorter or longer than what's considered the normal duration of menses days.
  • An equal number of women also experience non-period spotting and more than 80% of women get a white discharge.
  • About half of all the women in the world experience some form of Premenstrual Syndrome (PMS) in the few days before their bleeding begins.
  • Mood swings are one of the commonest PMS symptoms.

What are the hormones working in the menstrual cycle?

  • Estrogen and progesterone control all the preparation work for expected pregnancy and periods. FSH works on stimulating the follicles, and tiny sacs in the ovaries that contain an oocyte (egg) each. Though several follicles are stimulated, it's the dominant follicle that finally releases the egg.
  • LH works together with FSH during the follicular phase, but their levels rise and fall differently during the follicular phase.

Why is it important to study the menstrual cycle?

Understanding what a normal menstrual cycle is, is one of the most important things about being a woman; understanding how it works, and knowing about the causes of irregular menstruation, can help with detecting any underlying health problems, such as PCOS, or even cancer.

1. Regular vs irregular causes of irregular menstruation

When it comes to the length of periods, 'regular' and 'irregular' can vary by ethnicity and also with age. For example, immediately after puberty, as menstruation begins, periods are longer (can go up to even 10-12 days); with progressive age, this duration tends to get shorter.

Again, when a woman approaches menopause, the duration of the period and menstrual flow tends to get more irregular. Hot flashes are one of the commonest symptoms of perimenopause (the time before menopause).

2. Duration and menstrual flow

Periods coming at gaps shorter or longer than the 'regular' range of 21 days to 35 days may be considered 'irregular' if it's a persisting pattern. If the gap goes beyond 40 days, then it's time for a medical consultation.

The volume of menstrual flow also indicates if the periods are 'regular' or 'irregular'. While the same woman may experience heavier than usual flow one month and lighter than usual flow the next month, a steady pattern of excessively heavy flow (menorrhagia) or extremely light flow (spotting or scant periods) needs medical attention.

Women suffering from menorrhagia may experience a period duration of longer than 7 days, and those with light periods may see it ending within 2 days. The right food with health benefits can go a long way in regulating periods for any woman.

3. Late periods

Causes of a delayed period (or a missed period) can range from acute stress, sudden weight loss, or infection to pregnancy. Late periods are also common in teenagers or older women approaching menopause. Persistent late periods require a visit to an ob-gyn (obstetrician and gynecologist).

4. Contraceptives and diseases

Certain contraceptives, IUDs (intra-uterine devices), and specific disorders like Polycystic Ovary Syndrome (PCOS), uterine fibroids, endometriosis, Pelvic Inflammatory Diseases (PID), and various eating disorders can change the length of the menstrual cycle. Even normal conditions like pregnancy or breastfeeding can do this.

5. Keeping track

Ask yourself these questions to keep track of what's happening during your periods, and try to identify any patterns that'll tell you if the periods are normal or not.

  • What is the start date of the cycle/start date of the bleeding (period days)?
  • What is the nature of the bleeding or period?
    • Do you notice any blood clots?
    • Do you need to change your sanitary napkins often?
    • Do you notice only spotting, and not bleeding?
    • Is the flow volume very high?
  • What is the end period date of the bleeding? What are the total bleeding/period days?
  • What is the total number of menstrual cycle days (from the first day of the previous cycle to the first day of the next cycle)?
  • Is there any bleeding in between both the cycles?
  • Other factors to note:
  • Intensity of pain
    • Moderate / barely tolerable / excruciating
    • Inconsistent / varying but continuous / consistently high
  • Mood swings
    • Negligible change/swings a lot / consistently depressed
  • Behaviour
    • Well under control / often shoots off / uncontrollably erratic
  • Hot flushes

By analyzing the answers to the questions above, a doctor can diagnose if a patient's menstrual aspects are normal or abnormal. The range of normalcy is not narrow, so there is no need to get nervous about small changes.

What to watch out for

Every woman must consult her doctor if she observes the following situations:

  • If the bleeding pattern (number of days or the volume) changes suddenly.
  • If the number of days of the cycle keeps varying every time.
  • If the period cycles are less than 20 days or more than 40 days away from each other.
  • If bleeding happens in between cycles.
  • Despite no pregnancy, the period does not happen for more than 90 days.
  • If the pain is intolerable/excruciating with or without fever.


After being explained what's normal in a menstrual cycle, and what's not, Nan was overwhelmed and thanked her doctor. She knew that this information would help every woman whose mind is plagued by doubts and questions.

Taking care of menstrual health is a decades-long responsibility for any woman, starting from teenage to nearly middle age. The more she knows about how the reproductive system functions, the better her chances of leading a healthy life.

Keep reading our blogs for more credible information on menstrual health.


Dr. Pramod Mane

A Doctor of Medicine (MD) in Pharmacology., currently based in Mumbai, India, Dr Pramod Mane, comes with an experience of more than 20 years of working in Medical Affairs in the Pharmaceuticals & Nutraceutical Industry. Director of Medical Services at Mega Lifesciences since 2008, Dr Mane has been associated with several MNCS in the areas of Medical Affairs, Medical Services, Medico-marketing, Pharmacovigilance & Clinical trials in his illustrious career.

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Current Version

Aug, 01 2023

Written By

Dr. Pramod Mane