Topic guide · Periods

Irregular, heavy or painful periods, explained

Written by the Femwise editorial team · Updated 7 October 2026

What's normal, what isn't, and when a change is worth a doctor's visit.

Quick answer

In adults, a period usually comes every 21 to 35 days and lasts up to seven days. Periods that are often irregular, very heavy or very painful, or that stop for three months, are worth checking with a doctor, because they can point to PCOS (now called PMOS), a thyroid problem, fibroids, endometriosis or other conditions that can be treated.

What's normal?

Usually normal

Worth checking with a doctor

Time between periods

21 to 35 days

Often under 21 or over 35 days, or none for 3 months

Length of bleeding

Up to 7 days

More than 7 days

Flow

Heavier for the first day or two

Soaking a pad every hour or two, or passing large clots

Pain

Cramps that ease with rest or a hot-water bag

Pain that stops you doing everyday things

First guides

Coming soon

Irregular periods: causes and when to worry

Coming soon

Heavy periods: what's too much?

Coming soon

Period pain: what helps, and when it's more than cramps

Coming soon

PMS: the week before your period

Coming soon

How to track your cycle

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Period tracker

See your average cycle and how much it varies.

Open the tool →

✓

PCOS symptoms checklist

10 questions, 2 minutes, no diagnosis.

Open the tool →

Sources

· Heavy menstrual bleeding, NICE guideline NG88
· Abnormal uterine bleeding, FIGO classification (PALM-COEIN)

Our reviewers check the medical facts on this page. They don't review or endorse our products.

This guide is for general information and doesn't replace advice from your own doctor.

Irregular periods? Check your other signs.

Take the free PCOS checklist