The menstrual cycle is the series of hormonal and physical changes that prepare the body for a possible pregnancy. It starts on the first day of a period and ends the day before the next period begins.
The cycle is commonly described in four phases: menstruation, the follicular phase, ovulation and the luteal phase.
Understanding the basics can help you recognise your own pattern, prepare for your period and notice when something has changed enough to be worth discussing with a healthcare professional.
This illustration uses a 28-day cycle as an example. Cycle length and the timing of ovulation vary between people and from one cycle to another.
Key takeaways
- The menstrual cycle starts on day 1 of your period. Count from the first day of one period to the first day of the next.
- A typical adult cycle lasts 21–35 days. A 28-day cycle is just a commonly used example, not a requirement.
- Menstruation overlaps with the follicular phase. The follicular phase begins on day 1 of your period and continues until ovulation.
- Ovulation doesn't always happen on day 14. Its timing varies between people and from one cycle to another.
- Cycle symptoms are individual. Some people notice changes in discharge, pain, appetite, mood or energy while others notice very little.
- Your own pattern matters. Very heavy or prolonged bleeding, bleeding between periods or after sex, periods that stop unexpectedly or severe pain are all worth discussing with a GP.
Contents
- What is the menstrual cycle?
- How long does a menstrual cycle last?
- What are the four phases of the menstrual cycle?
- How do hormones influence the cycle?
- What symptoms can change throughout the cycle?
- How can you track your menstrual cycle?
- When should you seek medical advice?
- Frequently asked questions
What is the menstrual cycle?
The menstrual cycle is a coordinated process involving the brain, ovaries and uterus.
Hormones signal changes that help an egg develop, may trigger its release from an ovary and prepare the lining of the uterus for a possible pregnancy.
If pregnancy doesn't occur, hormone levels change and the uterine lining sheds. The resulting blood and tissue pass through the cervix and vagina as a period.
If some of the terminology is unfamiliar, our menstrual health glossary explains the common terms.
Although pregnancy is one possible outcome of the cycle, your menstrual cycle isn't simply a monthly fertility test. Cycle patterns can be influenced by age, hormonal contraception, pregnancy, breastfeeding, stress, illness, changes in weight, exercise, medicines and other health factors.
What is the difference between a period and a menstrual cycle?
Your period is the bleeding that occurs when the uterine lining sheds.
Your menstrual cycle includes the whole process from the first day of one period until the day before the next period starts.
For example, if your period begins on 1 June and your next period begins on 29 June, your cycle is 28 days long. The days you actually bleed are only one part of those 28 days.
How long does a menstrual cycle last?
A typical adult menstrual cycle lasts around 21 to 35 days.
You often hear 28 days used as the example, but plenty of healthy cycles are shorter or longer than that.
Your cycle may also vary slightly from month to month. What matters is your usual pattern and whether something changes significantly.
Cycles are often more irregular during the first few years after periods begin. They can also change after pregnancy, while breastfeeding, when starting or changing hormonal contraception and during perimenopause.
A period itself typically lasts around 3 to 7 days.
Cycle length and period length are different things. Cycle length tells you how many days there are from the start of one period to the start of the next. Period length tells you how many days you bleed.
How do you count your menstrual cycle?
- Mark the first day of menstrual bleeding as day 1.
- Count each day until your next period begins.
- The first day of the next period becomes day 1 of the new cycle.
- Repeat this over several cycles to get a better idea of your usual pattern.
If your periods are irregular, tracking can still be useful. It gives you something concrete to show a healthcare professional rather than trying to remember dates and symptoms later.
What are the four phases of the menstrual cycle?
The menstrual cycle is commonly described in four phases: menstruation, the follicular phase, ovulation and the luteal phase.
These phases are useful for explaining what's happening biologically, but they're not four perfectly separate blocks of time. In particular, menstruation occurs during the early part of the follicular phase.
The timing also isn't fixed. A 28-day diagram with ovulation on day 14 is a teaching example, not a timetable your body has to follow.
| Phase | What's happening | What you might notice |
|---|---|---|
| Menstruation | The uterine lining sheds and menstrual bleeding occurs. | Bleeding, cramps, fatigue, bowel changes or very few symptoms. |
| Follicular phase | Follicles develop in the ovaries. Oestrogen generally rises and the uterine lining begins rebuilding. | Changes in cervical mucus or vaginal discharge, although symptoms vary. |
| Ovulation | A rise in luteinising hormone usually triggers release of an egg from an ovary. | Clearer or more slippery discharge, temporary one-sided discomfort or no noticeable signs. |
| Luteal phase | Progesterone rises after ovulation and supports the uterine lining in case pregnancy occurs. | Some people notice bloating, breast tenderness, appetite changes, headaches or mood symptoms. |
Menstrual cycle diagrams often use a 28-day cycle to show the sequence of events. Your own cycle may be shorter or longer and ovulation does not always occur on day 14.
1. Menstruation: your period
Menstruation marks the start of a new menstrual cycle.
If pregnancy hasn't occurred, oestrogen and progesterone levels fall and the uterine lining begins to shed.
Bleeding may start more heavily and become lighter over several days, although everyone's pattern is different. Menstrual fluid contains blood, tissue from the uterine lining and other fluids.
You might experience cramps, lower back discomfort, tiredness or changes in bowel habits. You might also feel relatively normal.
Period pain that repeatedly interferes with work, study, sleep, exercise or everyday activities shouldn't simply be accepted as something you have to put up with.
Practical tip: Track your bleeding, flow and any symptoms that matter to you. If you use reusable period care, choose a product based on your flow, anatomy, comfort and routine rather than assuming one option works for everybody. Our guide to choosing between a menstrual cup, disc or sponge can help.
Read more about the menstrual phase.
2. The follicular phase: preparing for ovulation
The follicular phase actually begins on the first day of your period and continues until ovulation. This means the menstrual phase and follicular phase overlap.
The brain releases follicle-stimulating hormone, or FSH, which supports the development of follicles in the ovaries. Each follicle contains an immature egg.
As follicles develop, oestrogen generally rises and the uterine lining begins to thicken again.
The length of the follicular phase is one reason menstrual cycle lengths vary. If ovulation happens later, the whole cycle will usually be longer.
You may notice your vaginal discharge changing as ovulation approaches. It can become wetter, clearer, more slippery or stretchier, although patterns vary.
Discharge can provide clues about where you are in your cycle, but discharge alone can't tell you exactly when ovulation has occurred. Read our guide to vaginal discharge and how it changes.
Practical tip: If you're curious about your own pattern, track discharge alongside your period dates and symptoms for a few cycles. Don't feel that you should have a particular mood, energy level or productivity level just because an app says you're in the follicular phase.
Read more about the follicular phase.
3. Ovulation: release of an egg
Ovulation happens when an ovary releases an egg, usually following a surge in luteinising hormone, or LH.
The egg enters a fallopian tube, where fertilisation may occur if sperm are present.
Ovulation is often described as happening in the middle of the cycle, but it doesn't reliably happen on day 14. It can occur earlier or later depending on the person and the individual cycle.
Some people notice clearer or more slippery cervical mucus, a temporary one-sided ache or other subtle changes around ovulation. Others don't notice anything at all.
Cycle-tracking apps may estimate when ovulation is likely based on previous cycle dates, but an app prediction can't confirm that ovulation actually occurred.
If you're trying to conceive, the days before ovulation matter too. Sperm can survive inside the reproductive tract for up to around 5 days, while an egg can usually be fertilised for about 12 to 24 hours after ovulation.
Important: An app or calendar prediction shouldn't be relied on as contraception. Fertility awareness methods involve more than counting days and require careful, consistent use. See our guide to contraception options in Australia if pregnancy prevention is important to you.
Read more about the ovulatory phase.
4. The luteal phase: after ovulation
After ovulation, the follicle that released the egg becomes a temporary structure called the corpus luteum.
The corpus luteum produces progesterone, which helps maintain the uterine lining in preparation for a possible pregnancy.
If pregnancy doesn't occur, the corpus luteum breaks down, progesterone and oestrogen fall and the next period begins.
The luteal phase tends to vary less in length than the follicular phase, but it isn't identical for everyone.
Some people notice symptoms in the days before their period, including bloating, breast tenderness, headaches, appetite changes or changes in mood. Others notice very little.
Premenstrual symptoms are real, but they aren't inevitable and they shouldn't automatically be dismissed as “just hormones”. If symptoms regularly affect your relationships, work, study, sleep or quality of life, it's worth talking about them with a healthcare professional.
Practical tip: If symptoms seem to appear before your period each month, record when they begin, when they improve and how much they affect your daily life.
Read more about the luteal phase.
How do hormones influence the menstrual cycle?
Hormones act as chemical messengers and help coordinate what's happening in the brain, ovaries and uterus.
Some of the main hormones involved are:
- Follicle-stimulating hormone (FSH): supports the development of follicles in the ovaries.
- Luteinising hormone (LH): a surge in LH usually helps trigger ovulation.
- Oestrogen: generally rises as a follicle develops and helps rebuild the uterine lining.
- Progesterone: rises after ovulation and helps maintain the uterine lining in preparation for a possible pregnancy.
These hormones work together rather than acting independently, and their levels don't follow an identical pattern in every person or every cycle.
Do hormones control your mood and energy?
Hormonal changes may be associated with physical and emotional symptoms, but they don't dictate exactly how you will feel during each phase.
A review of 47 prospective studies looking at mood across menstrual cycles didn't find one consistent negative mood pattern that applied to the general population.
That doesn't mean PMS or PMDD aren't real. Some people experience significant recurring symptoms in the luteal or premenstrual phase and deserve proper assessment and support.
Read about premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD).
You may also see the menstrual cycle described as four “seasons”. This can be a useful metaphor for thinking about your own cycle, but spring, summer, autumn and winter aren't medical phases and they don't prescribe how you should eat, exercise, work or feel.
Our individual phase guides explore that idea as a reflective framework rather than a set of rules.
What symptoms can change throughout the menstrual cycle?
You might notice changes such as:
- vaginal discharge or cervical mucus
- menstrual bleeding
- cramps or pelvic discomfort
- breast tenderness
- bloating
- headaches
- bowel changes
- skin or acne changes
- tiredness or sleep changes
- changes in mood or appetite
Not everyone experiences these changes, and not every symptom that happens during a particular phase is necessarily caused by the menstrual cycle.
Timing can provide useful information, but it doesn't establish a diagnosis on its own.
Does everyone experience the same cycle?
No.
Cycle length, period length, flow, pain, discharge and other symptoms vary between people. Your own cycle can also change over time.
Hormonal contraception can change the pattern considerably. Some methods suppress ovulation, change bleeding or stop bleeding altogether, so the pattern you experience while using hormonal contraception may not reflect a natural ovulatory cycle.
Pregnancy, breastfeeding, medicines, illness and perimenopause can also affect your cycle.
A late or missed period doesn't automatically mean pregnancy, but pregnancy is one possible explanation if it's relevant to you. Consider taking a pregnancy test and seek advice if you're unsure about a change.
How can you track your menstrual cycle?
Tracking can help you understand what's usual for you.
You can use a paper diary, calendar or digital period-tracking app. You don't need to record everything for tracking to be useful.
You might record:
- Period dates: the first day of each period and the number of days between periods.
- Bleeding: how many days you bleed, how heavy it feels and whether you notice spotting.
- Symptoms: cramps, headaches, bowel changes, fatigue, sleep changes or mood symptoms.
- Discharge: recurring changes you want to understand.
- Context: things such as starting contraception, illness or a change in medication.
Look for patterns over several cycles rather than drawing conclusions from one month.
Tracking can help you prepare for your period and gives you clearer information to share with a healthcare professional if something changes.
Digital apps often use previous cycle dates to predict future periods and ovulation. Those predictions are estimates rather than guarantees.
If you use an app, it's also worth looking at its privacy settings and how it stores or shares reproductive health information. Read our guide to period tracker apps.
If you prefer paper, you can download Period Shop's free printable period tracker.
When should you seek medical advice?
Cycle variation is common, but symptoms that interfere with everyday life deserve attention.
Speak with a GP or another qualified healthcare professional if:
- you need to change a pad or tampon every 1 to 2 hours because of heavy bleeding
- you need to change period products during the night or regularly bleed through clothes or bedding
- you repeatedly pass clots larger than a 50 cent coin
- your period regularly lasts longer than about 8 days
- you have bleeding between periods
- you have bleeding during or after sex
- you have any vaginal bleeding after menopause
- your periods stop for 3 months or more and pregnancy isn't the explanation
- your cycles are repeatedly shorter than 21 days or longer than 35 days
- period pain is severe, worsening or regularly stops you doing your usual activities
- you feel unusually tired, pale, dizzy or short of breath, particularly with heavy bleeding
Heavy menstrual bleeding is defined largely by how much it affects your physical, emotional, social and everyday life rather than requiring you to measure a particular volume of blood.
If bleeding suddenly becomes extremely heavy and you feel faint, weak or seriously unwell, seek urgent medical care. Call triple zero (000) if you faint or feel you may lose consciousness.
If you're a teenager, irregular cycles are common during the first few years after your first period. It's still worth speaking with a doctor if your first period hasn't arrived by around age 16, your periods stop for 3 months or more, your bleeding is very heavy or period pain significantly affects your life.
You don't have to wait until a symptom becomes severe before asking for help.
Frequently asked questions
Is a 28-day cycle the only normal menstrual cycle?
No. A 28-day cycle is a useful example, not a rule. A typical adult menstrual cycle can range from around 21 to 35 days. Your own usual pattern and significant changes from it are often more useful than comparing yourself with a 28-day textbook cycle.
Does ovulation always happen on day 14?
No. Day 14 is based on a simplified 28-day cycle example. Ovulation can happen earlier or later and its timing can change between cycles.
Can you have period symptoms before bleeding starts?
Yes. Symptoms such as cramps, breast tenderness, bloating, headaches or mood changes may occur before menstrual bleeding begins. Persistent or unusual symptoms can have other causes, so discuss them with a healthcare professional if you're concerned.
Can you get pregnant during your period?
Yes, pregnancy is possible from sex during menstruation. Sperm can survive for up to around 5 days, so pregnancy can occur if ovulation happens soon after sex, particularly with shorter or irregular cycles. Period timing alone shouldn't be relied on as contraception.
Does everyone notice mood or energy changes during the menstrual cycle?
No. Some people notice recurring changes while others notice little or no difference. There isn't one mood, energy or productivity pattern that applies to everyone.
What's the difference between cycle length and period length?
Cycle length is the number of days from the first day of one period to the first day of the next. Period length is the number of days you actually bleed.
Is it useful to track my cycle if my periods are irregular?
Yes. Tracking irregular periods can help you see changes and give your healthcare professional useful information. Tracking by itself can't tell you what's causing the irregularity.
Understanding your cycle, one step at a time
Your menstrual cycle is a changing biological process, not a fixed monthly schedule that you need to follow perfectly.
Learning the basics can help you understand what's usual for your body, prepare for your period, choose period care that suits your needs and recognise when something may deserve a closer look.
If you'd like to understand your flow better, read our guide to how much you bleed during your period.
Explore each phase
If you'd like to go deeper, explore each stage of the menstrual cycle:
The menstrual phase
Learn more about what happens during your period and how this stage fits into the wider menstrual cycle.
The follicular phase
Explore follicle development, rising oestrogen and the lead-up to ovulation.
The ovulatory phase
Learn what happens around ovulation and why the timing isn't always day 14.
The luteal phase
Explore what happens after ovulation and why some people notice premenstrual symptoms during this stage.
Sources and further reading
- healthdirect: Menstruation
- healthdirect: Irregular periods
- healthdirect: Heavy periods
- healthdirect: Fertility awareness
- Better Health Channel: The menstrual cycle
- Australian Commission on Safety and Quality in Health Care: Heavy Menstrual Bleeding Clinical Care Standard
- Romans et al. Mood and the menstrual cycle: a review of prospective data studies
This article provides general health information and isn't a substitute for individual advice from a qualified healthcare professional.