PCOS, cycles
Irregular periods: normal variation, or worth a visit?
Cycles wander for all sorts of ordinary reasons. Here is the range usually considered normal, and the changes that deserve an appointment.
Reviewed against ACOG, 2 mins read, published

Almost nobody runs to the same number every month. The useful question is not whether your cycle varies, but by how much, and whether it changed.
What counts as normal
For adults, somewhere between 21 and 35 days is generally considered within the usual range, and a few days of drift across the year is unremarkable.
The normal length of the menstrual cycle is typically between 21 and 35 days. A normal menstrual period generally lasts up to 7 days.
What can push a period later
Illness, travel across time zones, weeks of poor sleep and sustained stress can all delay ovulation, which pushes that month's period later. The cycle stretches; nothing is broken.
Take a few months of dates with you. It turns a vague sense of things being off into something a clinician can actually work with.
Quick summary
- Usual range: 21 to 35 days for adults, with a few days of drift
- Can delay a period: illness, travel, poor sleep and sustained stress
- Worth an appointment: a change in your pattern, bleeding between periods, or none for three months
- Bring: a few months of dates


