Menstruation is the shedding of the lining of the uterus, also called the endometrium, along with bleeding. This is a natural process that happens every month during a woman’s reproductive years, except during pregnancy, menopause, or certain health conditions. The menstrual cycle is regulated by hormones released by the pituitary gland and ovaries, which work together in a coordinated way.
Menstruation usually begins during puberty, between the ages of 8 and 14 years, and continues until menopause, which typically occurs between 40 and 50 years. The average menstrual cycle length is about 28 days, but cycles ranging from 21 to 35 days can still be completely normal. Understanding this cycle can help you feel more confident, informed, and connected to your body.
Key takeaways
- The menstrual cycle is a natural monthly process controlled by hormones
- A normal cycle ranges from 21 to 35 days
- It includes four phases: menstrual, follicular, ovulation, and luteal
- Ovulation is the most important phase for conception
- Tracking your cycle helps you understand your fertility better
- Tools like Premom can simplify cycle tracking and improve awareness
Phases of the menstrual cycle
The menstrual cycle is divided into four phases. Each phase plays an important role in preparing your body for a possible pregnancy and maintaining hormonal balance.
- Menstrual phase or menstruation
- Follicular phase or proliferative phase
- Ovulation phase
- Luteal phase or secretory phase
Let us understand each phase simply and clearly.
1. The menstrual phase
The menstrual phase is the first phase of the cycle and begins on the first day of your period. During this time, the uterine lining sheds and exits through the vagina. The discharge includes blood, mucus, and cells from the lining of the uterus.
This phase usually lasts between 3 and 7 days. Hormone levels, especially estrogen and progesterone, are low during this time, which is why you may feel low in energy or experience mild discomfort like cramps. This phase is your body’s natural way of resetting and preparing for a new cycle.
2. The follicular phase
The follicular phase begins on the first day of your period and continues after your bleeding stops. It typically lasts around 13 to 14 days. During this phase, the anterior pituitary gland releases two important hormones into the bloodstream: Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH).
FSH stimulates the ovaries to develop follicles, each containing an immature egg. At the same time, estrogen levels begin to rise, which helps rebuild the uterine lining. LH remains at a steady level for most of this phase and plays a key role later in the ovulatory process.
You may notice a gradual improvement in your energy and mood during this phase as hormone levels increase and your body prepares for ovulation.
3. The ovulation phase
Ovulation occurs when a fully developed egg is released from the ovary and begins its journey through the fallopian tube toward the uterus. This process is triggered by a surge in Luteinizing Hormone (LH), which typically lasts for about 24 hours.
Ovulation usually happens once a month, around the middle of your cycle, although the exact timing can vary. Once released, the egg survives for up to 24 hours. This is the most important time for conception, because if sperm meets the egg during this window, the chances of pregnancy increase.
Sperm can live in the female body for up to 3 to 5 days, which creates a fertile window of about 5 to 6 days. Tracking this window can help you plan intercourse more effectively.
Premom helps you track your LH surge and understand your ovulation patterns more clearly. By identifying your most fertile days, you can feel more confident and supported in your fertility journey.
4. The luteal phase
After ovulation, the body enters the luteal phase. During this phase, the ruptured follicle in the ovary forms a structure called the corpus luteum. This structure releases progesterone and a small amount of estrogen.
These hormones help thicken and maintain the uterine lining, making it ready to support a fertilised egg. If pregnancy does not occur, the corpus luteum gradually breaks down, leading to a drop in progesterone levels.
As hormone levels fall, the uterine lining sheds, and menstruation begins again, starting a new cycle. This phase usually lasts about 12 to 14 days and is an important part of maintaining cycle regularity.
Tracking this phase with Premom can help you better understand your hormonal patterns and support your chances of conception in a more informed way.
Hormones in the four phases of the menstrual cycle
| Phase | Main Hormones Involved | What happens to hormones | Effect on the body |
| Menstrual phase | Estrogen, Progesterone | Both hormones are low | Uterine lining sheds, causing your period |
| Follicular phase | FSH, Estrogen | FSH rises, and estrogen gradually increases | Eggs begin to develop, uterine lining starts to rebuild |
| Ovulation phase | LH, Estrogen | Sudden LH surge, high estrogen | An egg is released from the ovary |
| Luteal phase | Progesterone, Estrogen | Progesterone rises, and estrogen is moderate | Uterine lining thickens to support a possible pregnancy |
At what age does menstruation typically begin?
Menstruation usually begins around the age of 12, but it can start as early as 8 years or as late as 16 years, which is still considered normal. Most people begin menstruating within a few years after the development of breast tissue and pubic hair, as these are signs that the body is going through puberty and hormonal changes.
Menstruation continues throughout the reproductive years and gradually stops at menopause, which typically occurs between the ages of 45 and 50. Menopause is reached when a woman has not had a menstrual period for 12 consecutive months, marking the end of ovulation and the natural reproductive phase.
What is considered an irregular period?
Irregular menstruation refers to any pattern that falls outside your usual cycle or the normal range of 21 to 35 days.
Some common signs of an irregular period include:
- Periods that occur less than 21 days or more than 35 days apart
- Not having a period for three months or longer
- Menstrual flow that is much heavier or lighter than usual
- Period bleeding that lasts longer than seven days
- Severe pain, cramping, nausea, or vomiting during periods
- Bleeding or spotting between periods
What causes irregular periods?
Irregular periods can happen for many reasons. Sometimes, it may be due to simple lifestyle changes like stress or weight changes. In other cases, it can be linked to underlying medical conditions that affect your hormones and reproductive system. Your menstrual cycle depends on a balance of hormones. When this balance is disturbed, your periods may become irregular, delayed, or even stop for some time.
Medical conditions that can cause irregular periods
Certain health conditions can affect your cycle and lead to missed or irregular periods:
- Endometriosis: This happens when tissue similar to the uterine lining grows outside the uterus. It can cause heavy bleeding, severe cramps, and pain before or during periods.
- Pelvic inflammatory disease (PID): This is a bacterial infection of the reproductive organs, often caused by untreated infections. It may lead to irregular periods, pelvic pain, and unusual discharge.
- Polycystic ovary syndrome (PCOS): In this condition, the ovaries produce higher levels of male hormones. This can delay or stop ovulation, leading to irregular or missed periods.
- Primary ovarian insufficiency: This occurs when the ovaries do not function properly before the age of 40. It can lead to irregular or absent periods.
- Thyroid or pituitary disorders: Conditions like an underactive or overactive thyroid can disturb hormone levels and affect your cycle.
- Bleeding disorders: These can cause unusually heavy or prolonged menstrual bleeding.
- Reproductive cancers: Conditions like uterine or ovarian cancer may cause abnormal bleeding or changes in menstrual patterns.
Lifestyle factors that can affect your cycle
Your daily habits and overall health also play a big role in regulating your periods.
- High levels of stress
- Sudden weight gain or weight loss
- Very intense exercise or low body fat
- Illness or infections
These factors can temporarily disrupt your hormones and affect your cycle.
Other causes of irregular periods
Some additional factors can also lead to changes in your menstrual cycle:
- Birth control pills: Starting or stopping them can cause irregular or missed periods for a few months
- Certain medications: Such as steroids or blood thinners
- Pregnancy-related changes: Including miscarriage or ectopic pregnancy
- Breastfeeding: Hormones during this time can delay periods
- Surgery or scarring: In the uterus, ovaries, or fallopian tubes
What is premenstrual syndrome (PMS)?
Premenstrual syndrome, or PMS, refers to a group of physical and emotional symptoms that usually begin about one to two weeks before your period. These symptoms are quite common, and many women notice at least one sign that helps them recognise their period is approaching. Symptoms typically improve or go away once the period starts and often follow a similar pattern in each cycle.
What are the symptoms of PMS?
PMS symptoms can be physical, emotional, or a combination of both. They may range from mild to severe and do not affect everyone in the same way.
Physical symptoms may include:
- Bloating or a gassy feeling
- Pelvic pain or discomfort
- Fatigue or low energy
- Acne flare-ups
- Breast tenderness
- Headaches
- Diarrhoea or constipation
Emotional symptoms may include:
- Irritability or feeling easily upset
- Mood swings
- Changes in sex drive
- Feeling anxious, sad, or having crying spells
- Difficulty concentrating or brain fog
- Food cravings or changes in appetite
- Trouble sleeping (insomnia)
If PMS symptoms are severe or begin to interfere with your daily life, it may be a condition called premenstrual dysphoric disorder (PMDD). In such cases, it is important to speak with a healthcare provider for proper support and guidance.
Why understanding your menstrual cycle is important
Understanding your menstrual cycle is not only helpful for pregnancy planning but also for overall health awareness. When you are familiar with your cycle, you can recognise changes early and take better care of your body.
Tracking your cycle regularly can help you:
- Identify your fertile window more clearly
- Understand hormonal changes and symptoms
- Notice irregular patterns early
- Share accurate information with your healthcare provider
Using tools like the Premom and easy@home LH Kits can help you track ovulation, identify your fertile days, and understand your cycle patterns more clearly.
FAQ’s about menstrual cycle
A normal menstrual cycle usually ranges from 21 to 35 days, although the average is around 28 days. It is important to understand that every woman’s body is different, and slight variations in cycle length from month to month can still be considered normal and healthy.
Not necessarily. While ovulation is often said to occur around the middle of the cycle, the exact timing can vary depending on individual hormone patterns and cycle length. This is why tracking ovulation using tools like LH tests can provide more accurate insights.
After ovulation, the egg usually survives for about 12 to 24 hours. This is a short window, which is why timing is important when trying to conceive. However, since sperm can survive for several days, the fertile window extends beyond just the day of ovulation.
Yes, it is still possible to get pregnant with irregular cycles, but identifying your fertile window may be more challenging. Tracking ovulation signs and using apps like Premom can help you better understand your cycle and improve your chances over time.
Tracking your menstrual cycle helps you understand when you are most fertile and how your body behaves throughout the month. It also helps you notice any irregularities early and provides useful information that you can share with your healthcare provider for better guidance.
Disclaimer: This article is for informational purposes only and is not a substitute for medical advice, diagnosis, or treatment. Always consult your healthcare provider for personalised guidance.
References:
- Office on Women’s Health. Menstrual cycle. U.S. Department of Health and Human Services. https://www.womenshealth.gov/menstrual-cycle. Accessed April 22, 2026.
- Cleveland Clinic. Menstrual cycle. https://my.clevelandclinic.org/health/articles/10132-menstrual-cycle. Accessed April 22, 2026.
- American College of Obstetricians and Gynecologists. The menstrual cycle. https://www.acog.org/womens-health/faqs/the-menstrual-cycle. Accessed April 22, 2026.
- MedlinePlus. Menstruation. National Library of Medicine. https://medlineplus.gov/menstruation.html. Accessed April 22, 2026.
- World Health Organisation. Sexual and reproductive health. https://www.who.int/health-topics/sexual-health. Accessed April 22, 2026.
