Temel Bilgiler
Are my periods irregular? When should I see a doctor?
Which cycles count as irregular, why a long gap without a period matters, what else besides PCOS can cause it and when to see a doctor. A plain guide based on the guideline.
Published · 6 min read
Does your period sometimes come after 28 days and sometimes after 50? You are not the only one. Irregular cycles are very common, and there is often an understandable reason behind them. In this article we explain in plain words which cycles count as "irregular", why long gaps matter and when it is time to see a doctor.
In short: Three years after your first period, cycles shorter than 21 or longer than 35 days count as irregular, and any single cycle longer than 90 days is reason enough to see a doctor. Irregular periods are one of the most common signs of PCOS, but not the only cause. Logging your periods regularly gives you the strongest data for that conversation.
How the cycle works
A cycle runs from the first day of one period to the first day of the next. Around the middle of the cycle, one of the ovaries releases an egg. This is called ovulation.
After ovulation, the body makes a hormone called progesterone. Progesterone prepares the lining of the womb for a possible pregnancy. If there is no pregnancy, progesterone falls and the lining is shed. That is your period.
In PCOS, the hormone balance can often disrupt ovulation. Without ovulation, progesterone does not rise either, so the period comes late or not at all. That is why irregular cycles are one of the three criteria used to diagnose PCOS [1]. PCOS affects an estimated 8–13% of women of reproductive age, and up to 70% of those affected worldwide have not been diagnosed [2]. Getting to know your cycle is an important part of getting to know your own health.
Which cycles count as irregular?
The 2023 International PCOS Guideline uses these limits, based on how long it has been since your first period [1]:
| Since your first period | Counts as irregular |
|---|---|
| Less than 1 year | Normal; irregularity is expected in puberty |
| 1–3 years | Cycles shorter than 21 or longer than 45 days |
| More than 3 years | Cycles shorter than 21 or longer than 35 days, or fewer than 8 periods a year |
| More than 1 year | Any single cycle longer than 90 days |
Diagnosis in adults
Irregular cycles alone do not mean PCOS. In adults, a diagnosis needs two of these three criteria [1]:
- Irregular cycles or problems with ovulation
- Excess androgens: signs such as noticeable hair growth or stubborn acne, or high levels on a blood test (androgens are the "male hormones" that women also have in small amounts)
- Polycystic ovaries on ultrasound, or a raised AMH (a blood test that reflects the egg reserve)
Other conditions that cause similar symptoms need to be ruled out first. If you have both irregular cycles and excess androgens, no ultrasound or AMH test is needed [1].
Diagnosis in teenagers
Because irregular cycles are normal in the first years after periods start, the rules are different for teenagers. Both irregular cycles and excess androgens are needed, and ultrasound and AMH are not used [1].
Why a long gap matters
Without ovulation, the lining of the womb is exposed to the hormone oestrogen without the balancing effect of progesterone. Over time this raises the risk of the lining thickening.
A meta-analysis (a study combining the results of many studies) found a roughly 2–3 times higher risk of endometrial cancer, the cancer of the womb lining, in women with PCOS [3]. That can sound scary, but the absolute risk is still low. The guideline does not recommend routine screening for everyone [1]. Still, going a long time without a period, or unexpected bleeding, is something to raise with your doctor.
The good news is that there are options. The guideline names the combined contraceptive pill as the first-line treatment for irregular cycles and excess androgens [1]. You and your doctor can decide together what suits you.
Not only PCOS
Irregular periods have other causes too. Your doctor will usually order blood tests to tell them apart. Common causes include:
- Pregnancy: the first thing to consider when a period is late.
- Thyroid problems: an under- or overactive thyroid gland can affect your cycle.
- High prolactin: a raised level of this milk-related hormone can suppress ovulation.
- Low energy, stress and intense exercise: when the body gets too little energy for a long time, or is under heavy stress or training, the brain can slow down ovulation and periods can stop [4].
- Medicines and hormonal methods: some medicines, or stopping a contraceptive method, can change your cycle for a while.
The second-to-last cause is known medically as "functional hypothalamic amenorrhoea". The hypothalamus is the part of the brain that directs hormones. It can sometimes look like PCOS, but the approach is different, which is why getting the right diagnosis matters.
When to see a doctor
- No period for more than 90 days
- Cycles consistently shorter than 21 or longer than 35 days
- Fewer than 8 periods a year
- Periods lasting more than 7 days or very heavy
- Bleeding between periods or after sex
- A sudden, unexplained change in your cycle
- Irregular cycles together with noticeable hair growth, stubborn acne or hair thinning
If you have very heavy bleeding, dizziness, feel faint or have severe abdominal pain, get urgent help without waiting.
What you can do
- Log your periods: note the start date, how many days it lasts and how heavy it is. After a few months, patterns start to show.
- Track your symptoms: add changes in acne, hair growth, mood, sleep and pain.
- Prepare for your appointment: write down your last 3–6 cycles, any medicines and supplements you take and the questions you want to ask.
- Eat enough: very restrictive diets can push the body into saving energy and disrupt your cycle further [4].
- Keep movement balanced: regular activity helps, but very intense training without rest can also affect your cycle [4].
- Be kind to yourself: an irregular cycle is not your fault. Asking questions and seeking a second opinion is your right.
Frequently asked questions
Do irregular periods always mean PCOS?
No. Many things can disrupt your cycle, including thyroid problems, high prolactin, stress and low energy. A PCOS diagnosis needs other criteria too, and other causes must be ruled out [1].
How do I judge my cycle while on the pill?
Bleeding on the pill is controlled by the pill and does not reflect your natural cycle. So regular bleeding does not mean there is no underlying condition. Talk to your doctor about when and how to stop the pill if you need a diagnosis or follow-up.
Do irregular periods mean I can't get pregnant?
No. Ovulation may be less frequent, but that does not mean it never happens, which is also why irregular cycles are not reliable contraception. If you are planning a pregnancy, talk to your doctor early; the guideline names letrozole as the first-line medicine to help you ovulate [1].
Does logging really help?
Yes. Being able to say "my cycles ranged from 38 to 70 days over the last six months" instead of "my periods are irregular" helps your doctor assess things much faster. Your logs also make it easier to see changes over time.
This article is for information only; talk to your doctor about diagnosis and treatment.
Sources
- Teede HJ et al. 2023 International Evidence-based Guideline for PCOS. Fertil Steril. 2023; 120(4): 767-793. PubMed
- World Health Organization. Polycystic ovary syndrome – Fact sheet. 2023. WHO
- Barry JA, Azizia MM, Hardiman PJ. Risk of endometrial, ovarian and breast cancer in women with PCOS: a systematic review and meta-analysis. Hum Reprod Update. 2014; 20(5): 748-758. PubMed
- Gordon CM et al. Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2017; 102(5): 1413-1439. PubMed
