Understanding the Menstrual Cycle: A Beginner's Guide
By Dr. Meera Iyer
Gynecologist & Sexual Health Educator · MBBS, MS (OBG), Mumbai
By Dr. Meera Iyer, Gynecologist and Sexual Health Educator, Mumbai
A 19-year-old patient asked me last week, "Doctor, why do I cry on day 22 of every month for no reason?" When I asked her if she tracked her cycle, she said, "I just know when my period comes."
Here's what's actually happening in your body: your menstrual cycle has four phases, and each one comes with different hormones, different moods, and different physical signs. Understanding them changes how you understand yourself.
If you grew up in India and got the standard "you're a woman now, here's how to use a pad, don't tell your brothers" speech — this guide is for you.
What Even Is a Menstrual Cycle?
Your menstrual cycle is the monthly rhythm your body follows to prepare for a possible pregnancy. The first day of your period is Day 1 of your cycle. The cycle ends the day before your next period begins.
A typical cycle lasts about 28 days, but anywhere between 21 and 35 days is medically normal. Cycles vary from person to person, and even from month to month for the same person.
According to NFHS-5 (2019-21), only about 57.6% of Indian women aged 15-24 use hygienic period products, and many girls never receive accurate information about what their cycles actually mean. This guide is here to fix that.
The 4 Phases of the Menstrual Cycle
Most medical textbooks divide the cycle into four phases. Let's go through them one by one.
Phase 1: Menstrual Phase (Days 1-5)
This is your period — the days you actually bleed.
What's happening: Your uterus is shedding its inner lining (called the endometrium) because no pregnancy occurred. The lining exits through the vagina, mixed with a small amount of blood. Total blood loss across the entire period is about 30-80 ml — much less than most people imagine.
How long it lasts: Usually 3-7 days. Anything longer than 7 days warrants a check-up.
Hormone levels: Estrogen and progesterone are at their lowest. This is why many people feel low energy, tired, or emotionally flat in the first 1-2 days.
Common physical signs:
- Cramps (caused by uterine muscle contractions to expel the lining)
- Lower back ache
- Breast tenderness easing
- Slight bloating
- Headaches in some
Common emotional signs:
- Wanting to rest more
- Lower mood on day 1-2 for some
- A sense of relief once bleeding starts (hormones begin shifting)
Self-care tip: This is the phase to slow down. Hot water bottles, warm food, gentle movement, and rest help with cramps. If your cramps are severe enough to prevent normal activities, please see a doctor — that's not just "bad luck."
Phase 2: Follicular Phase (Days 1-13)
This phase technically overlaps with your period at the start. It begins on Day 1 of your cycle and continues until ovulation.
What's happening: Your pituitary gland releases follicle-stimulating hormone (FSH). This signals your ovaries to begin maturing several follicles — small fluid-filled sacs that each contain an egg. Usually, one becomes dominant and continues developing while the others stop.
Hormone levels: Estrogen begins rising steadily. Progesterone stays low. As estrogen climbs, it starts thickening the uterine lining again to prepare for a possible pregnancy.
How you feel: Many people describe the late follicular phase as their best week of the month. Higher estrogen often correlates with:
- More energy
- Improved mood
- Clearer skin
- Higher libido (especially closer to ovulation)
- Better focus and verbal fluency
- Fewer cravings
Cervical mucus: Becomes increasingly clear, slippery, and stretchy as you approach ovulation. This is your body preparing to welcome sperm.
"The follicular phase is often when women feel most like themselves. It's a great time for new projects, intense workouts, and important meetings — if you're paying attention to your cycle." — Dr. Duru Shah, Gynaecologist and Founder of Gynaecworld, Mumbai
Phase 3: Ovulation (Around Day 14)
This is the shortest phase — and the only window in your cycle when you can get pregnant.
What's happening: A surge of luteinising hormone (LH) triggers the dominant follicle to release its mature egg. The egg travels down the fallopian tube. It lives for about 12-24 hours. If sperm meet it during this window, fertilisation can occur.
Sperm, however, can survive in the female reproductive tract for up to 5 days. This is why your "fertile window" is actually about 6 days long: 5 days before ovulation plus the day of ovulation itself.
How you might know you're ovulating:
- A slight twinge or ache on one side of your lower abdomen (called mittelschmerz — German for "middle pain")
- Cervical mucus is at its most clear, slippery, and stretchy (often described as raw egg-white texture)
- Slight rise in body temperature (about 0.3-0.5°C)
- Higher libido
- Slight breast tenderness
- Some people experience a brief, light spotting
Important: Ovulation does not always happen exactly on Day 14. In fact, it varies more than you might think. Tracking apps that assume Day 14 are often wrong for individual women.
Phase 4: Luteal Phase (Days 15-28)
The phase between ovulation and your next period. This phase lasts about 14 days for most women, and is the most consistent phase of the cycle.
What's happening: After releasing the egg, the empty follicle transforms into a structure called the corpus luteum ("yellow body"). The corpus luteum produces progesterone — the dominant hormone of this phase. Progesterone keeps the uterine lining thick in case a fertilised egg arrives to implant.
If pregnancy does not occur: The corpus luteum breaks down after about 12 days. Progesterone and estrogen drop sharply. The uterine lining is no longer maintained, and it sheds — your period begins.
How you feel:
- The early luteal phase often feels stable and calm (progesterone has a sedating effect)
- The late luteal phase (the last week before your period) is when most people experience PMS symptoms
- Mood changes, irritability, sadness, anxiety
- Bloating, breast tenderness, food cravings
- Acne breakouts
- Fatigue
- Lower libido
- Trouble sleeping
This is the phase where my patient was crying on Day 22. It's not random. It's hormones.
PMS isn't a personality flaw. It's a recognised medical reality. Up to 75% of women experience some PMS symptoms. About 5-8% experience severe PMS or premenstrual dysphoric disorder (PMDD), which is treatable.
"I tell my patients: track your cycle for 3 months. If you're crying or angry on the same days every month, that's information. We can help with PMS and PMDD — you don't have to suffer through it." — Dr. Anjali Kumar, Gynaecologist and Founder of Maitri Women, Gurugram
Why Tracking Your Cycle Matters
Here's what tracking gives you that nothing else can:
- Predicting your period so you're never caught unprepared
- Understanding your moods — knowing the difference between "I'm sad" and "I'm in my late luteal phase"
- Spotting irregularities early — sudden cycle changes can be the first sign of PCOS, thyroid issues, or stress
- Planning major events around your energy peaks
- Knowing your fertile window — for pregnancy, or for avoidance
- Catching health issues — heavy bleeding, missed periods, unusual pain, all become visible when you're paying attention
Free apps like Flo, Clue, and MIA Period Tracker are popular in India. Or simply use a notebook. The format doesn't matter — paying attention does.
What Counts as Normal?
A normal menstrual cycle, according to FOGSI (Federation of Obstetric and Gynaecological Societies of India), looks like this:
| Feature | Normal Range |
|---|---|
| Cycle length | 21-35 days |
| Period length | 3-7 days |
| Blood loss per cycle | 30-80 ml |
| Largest clots | Smaller than a 1-rupee coin |
| Cycle variation | Can vary by 2-7 days month to month |
When to See a Doctor
Please see a gynaecologist if you experience:
- Cycles consistently shorter than 21 days or longer than 35 days
- Periods lasting longer than 7 days
- Soaking through a pad/tampon every hour for several hours
- Passing clots larger than a 1-rupee coin
- Severe cramps that prevent normal activities
- Bleeding between periods
- Bleeding after sex
- Missing periods for 3 or more cycles (without pregnancy)
- Sudden, dramatic changes in your usual cycle
- Severe PMS symptoms that affect your work or relationships
- First period after age 16
- Periods that have stopped before age 40
These are not things to "wait and see." They are signs your body needs attention.
Things That Affect Your Cycle
Your cycle is sensitive. Many things can shift it temporarily:
- Stress — major life events, exams, work pressure
- Travel and time zones
- Significant weight changes (loss or gain)
- Intense exercise or sudden change in activity
- Diet changes — especially very low-calorie diets
- Illness or infection
- Sleep disruption
- Medications — including antidepressants, steroids, antibiotics
- Hormonal contraception (which actually creates artificial bleeding, not real periods)
- PCOS, thyroid issues, hyperprolactinemia — all medical conditions worth knowing about
A one-off late period is rarely cause for alarm. Persistent changes are worth investigating.
Period Care in India: A Quick Note
NFHS-5 reported that 78% of Indian women aged 15-24 use a hygienic period product. That number is rising every year, but it means roughly 22% of young Indian women still don't have access to safe period products. If that's you or someone you know, organisations like Goonj, MyMenstrualCup, and Pad Project India distribute free or subsidised products.
There's no shame in any product choice — pads, tampons, menstrual cups, or period underwear all work. Use what fits your body, your budget, and your lifestyle.
Frequently Asked Questions
Is a 28-day cycle the only normal cycle?
No. Anywhere from 21 to 35 days is normal. The "28-day cycle" is just the average, not the rule.
Can my period be late if I'm not pregnant?
Yes — stress, illness, weight changes, travel, exercise, and many other factors can delay periods. If you're sexually active, take a pregnancy test first. Then see a doctor if it's been more than 6-8 weeks.
Does the menstrual cycle affect my mood?
Yes. Estrogen, progesterone, and other hormones fluctuate throughout the cycle and can affect mood, energy, and even thinking patterns. This is biology, not weakness.
Can I get pregnant during my period?
It's very unlikely but not impossible — especially if you have short cycles. Sperm can live for 5 days, so sex on day 6 of a 22-day cycle could result in pregnancy if you ovulate early.
Why is my period suddenly different?
Many possible reasons: stress, hormonal changes, weight shifts, contraception, illness. If the change persists for 2-3 cycles, see a doctor.
What is the difference between period and menstruation?
They mean the same thing. "Menstruation" is the medical term, "period" is the everyday word.
Are period cramps normal?
Some cramping is normal. Cramps so severe that you cannot function, take painkillers daily, or miss school/work — that's not normal. Please see a gynaecologist. It could be endometriosis, fibroids, or other treatable conditions.
Your menstrual cycle is one of your body's most important biological rhythms — and one of the least taught in Indian schools. Learning yours is a small act of self-knowledge that pays dividends for life.
At Samjho, we believe every girl and woman deserves to understand her own body. Track your cycle. Ask questions. See a doctor when something feels off. There's no stupid question when it comes to your health.