Cycle phases: what happens during the four phases of your cycle

Some days everything feels easy, and on others even the laundry basket feels like too much. That's not always down to sleep or the time of the week. Often it comes down to where you are in your cycle. Four hormones rise and fall over the course of a month in a fixed order, and they don't just act on your uterus, they affect your sleep, skin, appetite, energy and mood.

This post walks through the four phases one by one. Not so you plan your calendar around them, but so you recognise your own pattern when you see it.

First things first: what is a cycle?

A cycle begins on the first day of your period and ends the day before the next one starts. So day 1 is the first day of proper bleeding, not the last day before it with just a few spots.

The 28 days from your biology textbook is an average, not a standard. For adult women, anything between roughly 24 and 38 days counts as normal, and even for the same woman, the length can vary by a few days from month to month. A 26 day cycle followed by a 31 day one isn't a sign that something's wrong. It's the norm.

Something important for everything that follows: it's almost always the first half that varies. The time after ovulation stays fairly constant in length for most women. If a cycle runs longer than usual, it's usually because ovulation was delayed, not the period.

Phase 1: the period

Roughly day 1 to 5. The uterine lining built up during the last cycle is shed. A period usually lasts 3 to 7 days, and it's heaviest on the first and second day.

Estrogen and progesterone are at their lowest point now. That's why many women feel tired and more withdrawn in the first few days. The cramps come from chemical messengers that make the uterus contract so the lining can detach. Heat, movement and, if needed, a painkiller help most people.

Something that surprises many: for some, mood actually lifts once bleeding starts. The tension of the previous days eases as soon as the hormones have dropped.

Phase 2: the follicular phase

From the end of your period to ovulation. Strictly speaking, it actually starts on day 1, because from that point several egg follicles begin maturing in the ovary. One of them wins out. It produces estrogen, and that estrogen makes the lining grow back.

Rising estrogen makes this the most pleasant stretch of the cycle for most women. Many report more energy, better sleep, clearer skin and more desire to be around people. Exercise often feels easier too. During these days, cervical mucus changes from thick and scarce to clear and stretchy.

This is also the phase that shifts around. Stress, illness, travel across time zones, eating too little or training very hard can push ovulation back, sometimes by days, sometimes by weeks. The cycle then simply gets longer without you noticing, until your period arrives later than expected.

Phase 3: ovulation

A single day, somewhere in the middle. A sharp surge of the hormone LH triggers it: the mature follicle bursts and the egg travels into the fallopian tube. There, it can be fertilised for about 12 to 24 hours. Because sperm can survive in the body for several days, the days beforehand are the fertile ones, not just the day itself.

Some women feel ovulation as a brief pull on one side of the lower abdomen, known as mid-cycle pain. Many feel nothing at all. Estrogen is at its peak now, and many feel most at ease in their skin during these days.

In a 28 day cycle, ovulation falls mathematically around day 14. In a 34 day cycle, it's more like day 20. So the rule of thumb isn't the middle of the cycle, it's about two weeks before your next period. And since nobody knows in advance exactly when that will be, any prediction of ovulation ahead of time is really just an estimate.

Phase 4: the luteal phase

From ovulation to your next period, usually 12 to 14 days. The empty follicle turns into the corpus luteum. It produces progesterone, which prepares the lining for a possible implantation. Body temperature during this time runs a few tenths of a degree higher than before.

Progesterone has a calming, sleep-inducing effect. Many sleep well in the first half of this phase and feel hungrier, and both are normal: your basal metabolic rate really is a bit higher now.

If nothing implants, the corpus luteum breaks down. Progesterone and estrogen fall, and in the days before your period, what's known as PMS shows up: sore breasts, bloating, cravings, poor sleep, irritability, sadness for no clear reason. About three out of four women know at least one of these. Then bleeding starts, and the cycle resets to day 1.

What about the pill, the ring or a hormonal IUD?

In that case, most of this doesn't apply. The combined pill, the ring and the patch all suppress ovulation. The bleeding during the break isn't a real period, it's a withdrawal bleed caused by the brief absence of hormones. There's no four phase cycle happening during this time.

With the hormonal IUD and the mini pill, it's a mixed picture: many women still ovulate and go through the phases, just with lighter bleeding or none at all. With a copper IUD, the cycle runs just as it would without any contraception.

Why it's worth knowing your own pattern

Not so you can plan out your month. The effect of hormones differs from woman to woman, and if you read that you're supposed to be bursting with energy on day 10, you'll just feel bad when you're not.

It's worth it for three other reasons:

• You recognise what recurs. If you keep notes on how you're feeling for three months, you'll see whether the bad days always fall in the same spot. That takes some of the sting out of them: it's day 25, not your life.
• You notice when something changes. A cycle that gets shorter over several months, bleeding that gets heavier, pain that's new: you'll only spot these if you have something to compare against.
• You'll have something concrete when you see your doctor. Every gynaecological appointment includes questions about your last period and cycle length. An answer backed by actual data is worth more than one from memory.

When you should get it checked out

A cycle is allowed to vary. Even so, these things belong in a doctor's office:

• Cycles that are consistently shorter than 24 or longer than 38 days
• No period for three months, when you're not pregnant or using hormonal contraception
• Bleeding that lasts longer than seven days, or is heavy enough that you need to change a pad or tampon every hour
• Bleeding between periods or after sex
• Pain that regularly disrupts your everyday life or doesn't respond to standard painkillers
• A mood before your period that dips so low it affects your work, relationships or your will to keep going. This has a name, PMDD, and it can be treated

None of this automatically means something serious is going on. It means someone qualified should take a look.

How Lunabia can help

In Childfree mode, it's all about your cycle and nothing else. No baby topics, no questions about wanting children.

You log when your period starts and ends. From the second cycle onward, the app calculates using your own average instead of 28 days. The cycle ring shows which day you're on and which phase you're in: period, before ovulation, fertile window, ovulation, after ovulation. You can also record how you're feeling each day and choose from eight symptoms, from headaches to cravings. None of this is required. An empty day is a valid day.

After a few months, your history will show what this post can only describe in general terms: your own pattern.

The app works without an account, in which case everything stays on your phone. It contains no ads and no third party tracking components, and before it stores anything, it asks for your consent in a dedicated step.

And to be clear: Lunabia is not a form of contraception and doesn't provide medical diagnoses. All information about periods, fertile days and ovulation is an estimate based on what you enter.