A cycle is considered irregular if it is consistently shorter than 21 days, longer than 35 days, or varies widely month to month. Common causes include PCOS, thyroid disorders, stress, weight change and perimenopause.
Most women experience an irregular cycle at some point, and an occasional variation is completely normal. Persistent irregularity, however, is worth investigating, because it is often a signal about what is happening elsewhere in the body.
In this guide, Op. Dr. Ayşet Jane Özcan explains what counts as an irregular period, the most common causes, how they are investigated and which symptoms mean you should see a doctor.
What Counts as an Irregular Period?
A typical menstrual cycle lasts between 21 and 35 days, counted from the first day of one period to the first day of the next. Bleeding usually lasts 2 to 7 days.
A cycle is considered irregular if it is consistently shorter than 21 days or longer than 35 days, if the length varies widely from month to month, or if periods stop for several months without pregnancy. Occasional variation of a few days is normal.
Common Causes of Irregular Periods
Irregular cycles usually reflect a disruption in ovulation. The most frequent causes include:
- Polycystic ovary syndrome (PCOS), the most common hormonal cause
- Thyroid problems, both underactive and overactive
- Significant weight gain or weight loss, and very low body fat
- Intense physical training
- High or prolonged stress
- Perimenopause, the transition towards menopause
- Hormonal contraception, especially when starting or stopping
- Structural causes such as fibroids or polyps, which more often cause heavy or between-period bleeding
In the first year or two after periods begin, and in the years approaching menopause, some irregularity is expected and usually needs no treatment.
Irregular Periods and Fertility
Irregular cycles often mean ovulation is happening unpredictably or not at all, which makes conceiving harder simply because the fertile window is difficult to identify or absent.
The encouraging part is that most causes of irregular ovulation respond well to treatment. Once the underlying reason is addressed, many women resume regular cycles and are able to conceive.
How Irregular Periods Are Investigated
Assessment begins with your cycle history and a gynaecological examination. Bringing a record of your recent cycle dates makes this considerably more useful.
An ultrasound examines the ovaries and the lining of the uterus, and blood tests check thyroid function and reproductive hormones. Together these usually identify the cause.
Treatment and Management
Treatment targets the underlying cause rather than the symptom. Where weight, exercise levels or stress are contributing, addressing these alone often restores regular cycles. Thyroid disorders are treated directly and cycles typically settle afterwards.
For PCOS, a combination of lifestyle measures and, where appropriate, medication is used to regulate the cycle. If you are trying to conceive, treatment can be directed at supporting ovulation instead.
When to See a Doctor
Book an appointment if your periods stop for three months or more and you are not pregnant, if cycles are consistently shorter than 21 or longer than 35 days, if bleeding is unusually heavy or lasts longer than 7 days, if you bleed between periods or after intercourse, or if you have been trying to conceive without success.
Op. Dr. Ayşet Jane Özcan investigates and treats menstrual irregularity in Bahçelievler, Istanbul, with an individual approach based on the underlying cause. You are welcome to book an appointment.
References
This article was prepared with reference to the following independent health sources.
