My Period Did Something Weird ...

Okay, real talk: I used to think that a "late period" just meant stress or that my body was being dramatic. I'd Google it, spiral into twelve tabs, close them all, and just... wait it out.

Here's what nobody really explained to me: not all cycle weirdness is the same, and not all of it is a crisis. Some of it is just your body doing its thing. Some of it is worth a conversation with your doctor. The trick is knowing the difference, and that's exactly what we're going to get into.

Quick baseline: A "normal" menstrual cycle falls somewhere between 21–35 days. Coming in a few days early or late every once in a while? Completely fine. But if your cycle is consistently doing something that feels off for you, that's when it's worth paying attention.

Also worth knowing: between 14–25% of women in their reproductive years experience some form of abnormal uterine bleeding¹. So if you've had a cycle that felt "wrong," you are very much not alone.

So What Even Counts as an Irregular Cycle?

An irregular cycle isn't just "late." It's anything that falls outside your personal normal, whether that's always arriving early, always arriving late, or just being completely unpredictable.

Here are the ones that actually have names (yes, these are real medical terms, and no, you don't need to memorize them):¹

• Oligomenorrhea: Your periods show up less than once every 35 days, your cycle is taking its time.
• Polymenorrhea: Your periods arrive with less than 21 days between them, your cycle is in a rush.
• Amenorrhea: Your periods have gone fully MIA for several months and you're not pregnant.
• Menorrhagia: Your period is very heavy and drags on for more than 8 days.
• Hypomenorrhea: Your period shows up but barely, light bleeding that lasts less than 2 days.

And here's the thing, it can be a combination of the above. Your cycle might be irregular AND heavy. Or infrequent AND light. Tracking what's happening is how you start to see the pattern, and patterns are what give you and your doctor something to actually work with.

What's Actually Causing It? (The Honest Breakdown)

Normal Life Transitions

During puberty and perimenopause², your hormones are either figuring themselves out or winding down. So irregular cycles during those phases aren't a red flag, they're just reality. If you remember your first few years of getting your period, you'll know: it was chaos. That's normal.

Perimenopause works similarly, you might have stretches of regular cycles interrupted by months of irregularity, until your period eventually stops altogether.

Hormonal Imbalances

PMOS - Polyendocrine Metabolic Ovarian Syndrome (previously known as PCOS) - is one of the most common culprits. It affects 1 in 10 women³ and usually shows up as infrequent or absent periods, driven by insulin resistance and higher-than-usual testosterone levels. If your cycles are very long or have just stopped, PMOS is worth asking your doctor about.

Your thyroid also has more influence over your cycle than most people realise. An underactive thyroid tends to produce delayed, scanty periods. An overactive one? More frequent and heavier periods. When your thyroid is off, your whole hormonal system feels it.

Uterine Factors

Conditions like fibroids, endometriosis, adenomyosis, or endometrial hyperplasia⁴ can all cause irregular or heavier bleeding. These aren't just "bad periods", they're structural things happening in your uterus that deserve proper attention. If your period pain has also gotten significantly worse alongside any irregularity, that's a signal worth flagging.

Stress & Lifestyle (Yes, It's Real)

A rough deadline, getting sick, sudden weight changes (in either direction), or going really hard at the gym can all push your period off by a week or so. Usually it self-corrects by the next cycle.

But long-term stress - the kind that comes with disordered eating, certain medications, or chronic illness - can cause long-term disruption. Your body, very rationally, decides that now is not the time to prioritise reproduction. It's not being difficult. It's being pragmatic.

Side note: if you're on medication and your cycle has changed since starting it, even something like antibiotics or antidepressants, that’s worth mentioning to your doctor. It's more common than you'd think.

Chronic Conditions

Conditions like diabetes, lupus, or kidney disease can create systemic inflammation⁵ that disrupts hormone regulation. You might have regular cycles most of the time, but flares or periods of higher stress on your body can throw things off. If you're managing a chronic condition and notice cycle changes, loop in your doctor, these things are connected.

Okay, But When Should I Actually See a Doctor?

Here's the part I wish someone had told me clearly: one weird cycle is usually fine. Two or three in a row? Time to take it more seriously.

Book an appointment if:

• You've missed two or more periods and aren't pregnant
• You've had irregularities across three or more cycles
• Your periods are consistently less than 21 days apart
• Your bleeding is heavier than usual
• You're bleeding between periods or after sex
• Your period pain has significantly worsened

Getting checked out early doesn't mean catastrophising, it means giving yourself the best chance of figuring out what's going on before it becomes a bigger deal. Sometimes the fix is genuinely simple. Sometimes it needs more investigation. Either way, you want to know.

The Bottom Line

Tracking regularly is how you build that awareness. Because the difference between "this is just a weird month" and "this has been going on for three cycles" is information you can only have if you're logging.

You don't need to become a hormone expert. You just need to know enough to recognise your pattern, and know when it's time to ask for help.

REFERENCES & CITATIONS

• References
• Whitaker, L., & Critchley, H. O. (2015). Abnormal uterine bleeding. Best Practice & Research Clinical Obstetrics & Gynaecology, 34, 54–65.
• Hoyt, L. T., & Falconi, A. M. (2015). Puberty and perimenopause: Reproductive transitions and their implications for women's health. Social Science & Medicine, 132, 103–112.
• Pundir, C., et al. (2020). The Prevalence of Polycystic Ovary Syndrome. Journal of Human Reproductive Sciences, 13(4), 261.
• Leal, C. R., et al. (2024). Abnormal uterine bleeding: the well-known and the hidden face. Journal of Endometriosis and Uterine Disorders, 6, 100071.
• Harris, B. S., et al. (2022). Systemic inflammation and menstrual cycle length in a prospective cohort study. American Journal of Obstetrics and Gynecology, 228(2), 215.e1–215.e17.