You check the calendar. Then you check it again. Your period was due days ago, and it's nowhere to be seen. Cue the spiralling.
Before you panic, take a breath: a late or missed period is incredibly common and pregnancy is far from the only explanation.
Your cycle is run by a delicate hormonal conversation between your brain and your ovaries, and all sorts of everyday things can nudge it off schedule. Here's what's really going on and what to do about it.
First, the science in one line
Each cycle, your brain signals your ovaries to release an egg (ovulation) and your period usually arrives around two weeks later. If anything delays or skips ovulation, your period simply shifts with it. So a "late period" is often really a late ovulation. Almost everything below works by interfering with that signal.
The most common causes of a late period
1. Pregnancy
The obvious one to rule out first if you're sexually active. A missed period is the classic early sign, so a test is the simplest way to take this off the table before you investigate anything else.
2. Stress
This is one of the biggest everyday culprits. When you're under pressure, emotionally or physically, your body produces more cortisol, which can suppress the hormones that trigger ovulation. The result: a period that arrives late or skips a month entirely.
3. A disrupted routine
Travel, jet lag, shift work, broken sleep, a big life change - anything that scrambles your body clock can scramble your cycle too. (If your period always seems to go rogue on holiday, that's exactly why.)
4. Changes in weight, diet or energy
Rapid weight loss or gain, very low body weight, or simply not eating enough can all interrupt ovulation. Your body is remarkably good at pressing pause when it senses energy is in short supply.
5. Intense exercise
Heavy training combined with under-fuelling can delay or even stop periods altogether. It is common among athletes and very active people. It's not the exercise alone; it's the mismatch between energy in and energy out.
6. Hormonal contraception
Starting, stopping or switching the pill, coil, implant or injection can lead to late, irregular or absent periods, sometimes for a few months while your body adjusts.
7. Underlying health conditions
Two of the most common medical reasons for irregular or missing periods are PCOS (polycystic ovary syndrome) and thyroid issues (both over- and under-active). These are very manageable once identified, which is exactly why getting checked matters!
8. Perimenopause
From your 40s (sometimes late 30s), it's natural for cycles to lengthen and become less predictable as your hormones begin to shift.
9. Illness or medication
A heavy cold, the flu, another acute illness or certain medications can all throw a single cycle off temporarily.
And sometimes? There's no dramatic reason at all. The occasional late period is simply normal natural variation. Your cycle isn't a perfectly timed machine.
What to do about a late period
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Take a pregnancy test first if there's any chance you could be pregnant.
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Look at your last few weeks. More stress than usual? Less sleep? A trip, an illness, a training push, a diet change? The cause is often hiding in plain sight.
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Support the basics. Protect your sleep, eat enough to properly fuel your body, move in a way that feels good rather than punishing, and ease off the stress where you can.
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Track your cycle for a few months. Knowing your own "normal" is the single best way to tell the difference between a genuine change and your usual variation.
When to see a doctor
A one-off late period rarely needs medical attention. But it's worth booking an appointment if:
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You miss three or more periods in a row
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Your periods are consistently irregular
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Your periods stop before age 45
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You have other symptoms alongside (severe pain, unusual discharge, excess hair growth or sudden weight changes)
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You're trying to conceive and your cycle is unpredictable
A GP can run some simple checks for things like PCOS or thyroid conditions, so you're not left guessing.
The takeaway
A late period is your body communicating, not malfunctioning. Stress, sleep, travel, training, weight and your overall health all feed into one finely tuned system.
And most of the time, things settle once life does. Learn your normal, look after the basics and don't be afraid to get checked if something feels genuinely off.
This is general information, not medical advice. If a late period is worrying you, a your GP or doctor is the right person to talk it through with.
Whenever it does arrive, be ready for it.
Keep Riley's clean, organic cotton tampons, pads and liners on hand so a surprise period is never a scramble.
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