Irregular periods with PCOS: how to track your cycle
With PCOS, ovulation can be late or skipped, so a period may be delayed by weeks. That is why regular period apps often get your "next period" wrong. Knowing your actual cycle lengths matters more than a prediction.
How to calculate cycle length
Cycle length is the number of days from the first day of one period to the day before the next one starts.
| Period started | Next started | Cycle length |
|---|---|---|
| Jun 27 | Jul 28 | 31 days |
| Jul 28 | Sep 4 | 38 days |
In this example the second cycle is longer than 35 days, so it counts as irregular.
What counts as irregular
The international PCOS guideline treats cycles shorter than 21 days or longer than 35 days, or fewer than 8 periods a year, as irregular in adults. If you often go three months or more without a period, let your doctor know.
Using your records at an appointment
Bring your last 3–6 start dates, cycle lengths, and your shortest and longest cycle. In Hormly you tap period days on the calendar; it shows cycle lengths, flags cycles outside 21–35 days, and gives a likely range for your next period instead of one exact date.
This guide is for information only and is not medical advice. Talk to your doctor about diagnosis and treatment.
Make irregular cycles visible
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