The menstrual cycle: Overview, what's normal, phases explained

What is menstruation?

First things first, what is menstruation? It’s another word for period or, in other words, your monthly bleed. To get a bit more technical, it’s the shedding of the lining of your uterus, which is expelled through the vagina – usually about once a month, although it varies from person to person.

What is a menstrual cycle?

Your period is just one aspect of the menstrual cycle. During your cycle, hormones in your body cause the lining of your uterus to thicken – which happens so that if you get pregnant, the fertilized egg cell can implant into your uterine lining. 

Around the mid-point of your cycle, an ovary releases an egg cell, this process is called ovulation. This egg moves down your fallopian tubes and waits for a sperm cell to fertilize it. If that happens, and the cell successfully implants into the uterine wall, then it results in pregnancy. And if an egg isn’t fertilized, your body breaks down the thickened lining of your uterus and sheds it, resulting in your period — and thus a new cycle begins.

Your menstrual cycle, then, describes this series of events as your body prepares for the release of an egg and its potential fertilization, followed by menstruation if there’s no successful fertilization. 

The menstrual cycle phases

If we break the menstrual cycle down further, it is actually composed of multiple phases: menstruation, the follicular phase, ovulation, and the luteal phase. These distinct menstrual cycle phases are unique in their roles. However, they all play pivotal parts in the cycle as a whole, and their cyclical nature means that each is essential to the other. It’s a fine balance of hormones and biological triggers that keeps the cycle going.

Menstruation

The cycle starts with menstruation. This is the cycle phase that everyone knows – as unlike other cycle phases, there are significant physical changes during this point, including getting your period. This phase begins on the first day of your period and ends on the last day of your period.

The follicular phase

The follicular phase begins on the first day of your period (overlapping with the menstruation phase) and ends with ovulation.

This is approximately 16 days long, but as all our cycles vary, so does the follicular phase. Hormones are released in this phase which triggers the growth of follicles in the ovaries. There is also a surge in the main female sex hormone, estrogen. A rise in this hormone stops the production of follicles, allowing them to mature. One follicle eventually becomes dominant and releases an egg cell.

Your basal body temperature is lower during the follicular phase. There is also an increase in luteinizing hormone right before ovulation. This can also be detected with an LH urine test, which can help confirm where you are in your cycle.

Ovulation

Ovulation is the release of a mature female egg cell from an ovary, which takes place at the end of the follicular phase. Typically, this happens around two weeks after your period – although it varies from woman to woman.

The luteal phase

The next stage of the menstrual cycle is called the luteal phase and takes place after ovulation and before your period. The dominant follicle, or corpus luteam, produces progesterone, which is a hormone that causes body temperature to rise. It’s this progesterone that also causes the uterus lining to soften and prepare to shed.

If the egg is not fertilized, the uterus lining sheds, leading to your period (and the start of a new cycle). It’s during this latter phase of the menstrual cycle, in the days leading up to your period, that PMS symptoms can occur.

How do I track my period?

Tracking your menstrual cycle and finding ovulation has many benefits. By knowing where you are in your unique cycle you’ll be able to predict your period and plan ahead for PMS and period cramps. 

There are several ways you can track your period:

• Marking the first day of each period on a calendar
• Using a menstrual cycle chart to track the first and last days of your period
• Period tracking apps which record the first and last days of your period, as well as information about symptoms
• Basal body temperature tracking, to help identify when you’re ovulating
• Cervical mucus tracking

Natural Cycles goes one step further. Our birth control app is used in combination with a basal body thermometer so you can track your cycle and know your daily fertility. Most other cycle-tracking apps are based on calendar days alone, which doesn’t give you the same accuracy. Furthermore, Natural Cycles is the only app of its kind to be FDA Cleared for use as birth control. 

How does the menstrual cycle work?

The menstrual cycle (or uterine cycle) is essential for reproduction, but it also plays a role in the wider landscape of our health. The menstrual cycle works with a fine balance of hormones that are released at key points in order to stimulate phases in the cycle. 

The uterine cycle is the reason we get periods and why we experience various symptoms, such as menstrual cramps. There’s much more to the menstrual cycle than menstruation. It’s just the (very important) tip of the iceberg.

At what age does menstruation typically begin?

Menstruation begins during puberty, which can vary from person to person. On average, menstruation starts between the ages of 12 and 13, but it can start as earlier or later – it all comes down to the individual. The age you start your period can depend on several factors, like nutrition, overall health, genetics, and environmental factors.

If menstruation hasn’t started by the age of 16, or if there are any other concerns about delayed puberty, it’s a good idea to consult with a doctor.

How long is the menstrual cycle?

The length of menstrual cycles varies. However, regular cycles are thought to be between 21 and 35 days in length. While 28 days has often been considered the average cycle length, our latest research into the menstrual cycle revealed that only one in eight women experience a 28-day cycle. 

It’s also worth keeping in mind that some menstrual cycles are very regular, and other cycles frequently change. There are also medical conditions such as PCOS and thyroid conditions which can cause fluctuation in cycle lengths, and you should speak to a healthcare professional if you think you may be affected, or have concerns about these.

How often should you get your period?

So, if the 28-day cycle is a myth, how often should you get your period? There’s no such thing as ‘typical’, as it’s so different from person to person. However, on average, most individuals will get their period every 28 to 35 days. Some might have shorter cycles and get a period every 21 days or so, while others might have much longer cycles, getting a period once every 45 days.

And, of course, some people have irregular cycles, meaning that their period doesn’t come at the same time every month. This can be down to various things, such as:

• Hormonal imbalance: Fluctuations in hormone levels, particularly estrogen and progesterone, can disrupt your menstrual cycle and result in an irregular period.
• Stress: High levels of stress can throw your cycle off and mean your period is all over the place.
• Weight change: Significant weight loss or weight can disrupt your hormone levels and cause irregular periods.
• Medications: Certain medications, like antidepressants, chemotherapy drugs, blood pressure medications, and antipsychotics, can cause irregular periods.
• Hormonal birth control: When you use hormonal birth control, you experience a withdrawal bleed rather than a true period – and the type of birth control can make your bleed more regular, less regular, heavier or lighter.
• Medical conditions: Underlying medical conditions such as PCOS, thyroid disorders (hypothyroidism or hyperthyroidism), endometriosis, uterine fibroids, pelvic inflammatory disease (PID), or reproductive system cancers can lead to irregular menstrual cycles.
• Perimenopause: As you approach menopause, typically in the late 40s to early 50s, hormone levels fluctuate, leading to irregular periods before menstruation stops altogether.
• Puberty: It can take a while for your periods to settle into a regular pattern when you’re going through puberty, so you may experience irregular periods for a couple of years.
• Breastfeeding: Hormonal changes are at play here too. When you start reducing the amount of breastfeeding you do (or if you’ve been breastfeeding for more than six months), your periods are more likely to settle down into a regular pattern again.

How long does a normal period last?

Everyone’s different, but a period usually lasts between 3 to 7 days. Some people might have shorter periods while others might have longer ones – and both can be considered ‘normal’. What’s really important is to understand what’s normal for you, and whether there are any significant changes to your period, whether in duration, intensity of bleeding, or the frequency. If you’re concerned, it’s always best to get it checked out with a healthcare professional.

What is considered an irregular period?

Irregular periods can be determined by their frequency, as well as the amount of bleeding, and the length of the period. Some things that might be considered irregular include:

• Periods that are less than 21 days or more than 35 days apart
• Not having a period for more than 90 days
• A very heavy or very light flow – compared to what’s normal for you
• A period that lasts longer than 7 days

It’s very common to have some irregularities in your cycle, but if you notice lots of changes or are concerned about any symptoms, you should always speak to a healthcare professional for advice and evaluation.

 How much should I bleed during my period?

When you’re on your period, it can look – and feel – like a lot of blood, but it’s probably not as much as you think. Most women lose between 20 to 90 ml of blood during their period, which equates to between one and five tablespoons. Of course, some of us will lose more blood than this, and some will bleed less. 

The bleeding will usually be at its heaviest in the first two days of your period. Some signs of heavy bleeding include having to change your pad or tampon after less than two hours or passing blood clots that are the size of a quarter or bigger. Remember that everyone is different, and you may even lose different amounts of blood from one cycle to the next but do speak to your doctor if you’re concerned.

When should I contact my healthcare professional about my period?

Periods are very personal – in that they’re different for everyone. But if you have any concerns about your menstrual cycle, you should always speak to your gynecologist or doctor. Some reasons to do so might be:

• If you haven’t started your period by age 16
• You have very heavy bleeding
• You don’t have a period for three months
• You’re bleeding more or less than usual
• You’re in severe pain when on your period
• You have bleeding between periods
• If you notice significant changes in the regularity of your cycle

More than a period tracker

At Natural Cycles, we’re dedicated to providing a birth control option that’s not only hormone-free but can also help you learn more about your unique menstrual cycle and wider reproductive health. As well as a certified form of contraception, you can also use Natural Cycles to plan pregnancy. Take our quiz and find out how Natural Cycles can support you on your fertility journey.