Short answer
Log the first day of every period, how long you bleed, and symptoms such as acne, extra facial or body hair, and mood, and keep logging when months pass without a period. With PCOS, cycles are often long or unpredictable, so a good tracker shows a range of likely dates for your next period, not one fixed day.
Key facts
- PCOS affects an estimated 10–13% of reproductive-age women, and up to 70% of women with PCOS worldwide don't know they have it.[1]
- For PCOS assessment, cycles count as irregular 3 or more years after your first period if they are shorter than 21 days, longer than 35 days, or fewer than 8 a year.[2]
- Adults are diagnosed when 2 of 3 features are present and other causes have been ruled out: irregular cycles or ovulation, high androgens (signs or blood tests), and polycystic ovaries on ultrasound or a high AMH blood level.[2]
What counts as an irregular cycle with PCOS?
The 2023 international PCOS guideline defines irregular cycles by how long it has been since your first period:[2]
| Time since your first period | Irregular if |
|---|---|
| Under 1 year | Irregular cycles are normal while puberty settles |
| 1 to 3 years | Cycles shorter than 21 days or longer than 45 days |
| 3 years up to perimenopause | Cycles shorter than 21 days or longer than 35 days, or fewer than 8 cycles a year |
| Over 1 year | Any single cycle longer than 90 days |
WHO notes that PCOS is the most common cause of anovulation among women globally
, meaning cycles in which no egg is released.[1]
What should you log with PCOS?
- Period start and end dates, and flow. These give your cycle lengths, the first thing a doctor will ask about.
- Signs of high androgens. Acne and extra facial or body hair are common PCOS signs.[1]
- Mood and energy. PCOS can affect emotional as well as physical well-being.[1]
- Ovulation signs if you're trying to conceive. LH tests and basal body temperature can show whether and when you ovulate; with long cycles you may need to test for more days.
- Medicines and big changes. Note when you start or stop a medicine so you and your doctor can see whether your cycle changed.
Why should PCOS predictions be a range, not a date?
Calendar predictions assume your next cycle will look like your average one. That works poorly when cycles are long or irregular, and even in a study of women with cycles of 23 to 35 days, ovulation day varied a lot for any given cycle length.[3] A range shows how uncertain the estimate is, so a "late" period is less alarming when your cycle is simply long.
When should you see a doctor?
- You go more than 90 days without a period, or have fewer than 8 periods a year.[2]
- You have irregular cycles together with acne or extra facial or body hair.[2]
- You're trying to conceive. ACOG recommends an infertility evaluation after 1 year of trying, or after 6 months if you're older than 35.[4] With irregular cycles, it is reasonable to ask sooner.
- Your periods are very heavy or last more than 7 days.[5]
Women with PCOS have a higher risk of longer-term problems such as insulin resistance and type 2 diabetes, so getting assessed matters even if you're not planning a pregnancy.[1]
How Preeo can help
Preeo has a PCOS mode for irregular cycles. Predictions are shown as a date range, not a single guess, and they adjust as you log. You can log flow, 35+ symptoms, moods and notes, see charts of your cycle length, and with Preeo Premium create a doctor-ready PDF report.
Free to download. Preeo Premium is an optional subscription. See all features.
Frequently asked questions
Can a period tracker diagnose PCOS?
No. PCOS is diagnosed by a clinician using your cycle history, signs or blood tests for high androgens, and sometimes an ultrasound or AMH test. A tracker helps you bring an accurate cycle history.
Why does my app keep saying my period is late?
Most apps predict from your average cycle length. If your cycles are long or vary a lot, a single predicted date will often be wrong. A date range is more realistic.
Should I use ovulation tests with PCOS?
They can help if you're trying to conceive, but long or irregular cycles mean more days of testing. If you're trying to conceive with irregular cycles, talk with a doctor early.
How many periods a year counts as irregular with PCOS?
For PCOS assessment, fewer than 8 cycles a year counts as irregular once it has been at least 3 years since your first period.
Related questions
Sources
- World Health Organization. Polycystic ovary syndrome (fact sheet). www.who.int
- Teede HJ, Tay CT, Laven JJE, et al. Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Journal of Clinical Endocrinology & Metabolism, 2023. pubmed.ncbi.nlm.nih.gov
- Johnson S, Marriott L, Zinaman M. Can apps and calendar methods predict ovulation with accuracy? Current Medical Research and Opinion, 2018 (two of the three authors worked for SPD Development Company, which develops Clearblue home fertility tests). pubmed.ncbi.nlm.nih.gov
- ACOG. Evaluating Infertility (patient FAQ). www.acog.org
- Centers for Disease Control and Prevention (CDC). About Heavy Menstrual Bleeding. www.cdc.gov
This guide was drafted with AI assistance. Each statistic links to the source listed above. Spotted an error? Email support@preeo.app.