How do I tell if my cycle is irregular?

Bottom lineTell if your cycle is irregular by tracking day 1 of several periods and comparing lengths: regular cycles stay in the 21 to 35-day range and vary only by a few days, while irregular ones swing widely or often fall outside that range; a little variation is normal, but see a doctor if cycles are regularly abnormal, you miss three or more periods, or bleeding is very heavy.

A cycle is considered irregular when its length varies a lot from month to month, or falls outside the usual range. The only way to know is to track and compare.

How to check

1. Record day 1 of several consecutive periods
2. Count each cycle length (day 1 to the next day 1)
3. Compare the numbers across a few months

What's regular vs irregular

• Regular: cycles fall in the 21 to 35-day range and vary only by a few days
• Irregular: cycle length swings widely (for example, by more than 7 to 9 days), or is often shorter than 21 or longer than 35 days
• Missed periods: going 6 weeks or more without bleeding repeatedly

A little variation is completely normal - irregularity is about a consistent lack of pattern.

Common causes

Stress, weight changes, over-exercising, PCOS, thyroid problems, perimenopause, and some birth control can all cause irregular cycles.

When to see a doctor

Check in if cycles are regularly outside the normal range, you miss three or more periods, bleeding is very heavy, or you bleed between periods or after sex.

Femora tracks your cycle length over time and flags when your pattern shifts, so irregularity is easy to spot.

Track your cycle: menstrual cycle calculator