Could irregular periods be PCOS?

PCOS is a common cause of irregular cycles. It's diagnosed using recognised criteria rather than a single test. A specialist can assess this.

When should I check irregular periods?

If the change is new, persistent, or comes with other symptoms such as excess hair, weight change or difficulty conceiving, it's worth reviewing.

Irregular Periods: Causes & When to Check

Name: Irregular Periods: Causes & When to Check | Gynaec.com.au
Creator: Dr Priya Sivadas
Published: 2026-07-05

Irregular periods: causes and when to check

Cycle length naturally varies, and the occasional irregular period is common. But a persistent change in your pattern is worth checking.

This page explains the common causes of irregular periods and when to seek advice.

Key points

Occasional variation is normal; a persistent change is worth checking.
Common causes include PCOS (also known as PMOS), thyroid changes and perimenopause.
Stress, weight change and some medications can play a role.
A review can identify anything treatable.

Last reviewed 5 July 2026

Common causes

Irregular cycles can have several causes. Identifying the reason helps guide what, if anything, is needed.

Polycystic ovary syndrome (PCOS)
Thyroid problems and some other hormonal causes, such as raised prolactin
Perimenopause
Stress, significant weight change, or some medications

When it matters

A new or persistent change in your cycle, very infrequent periods, or irregular bleeding with other symptoms is worth reviewing.

Diagnosis: what to expect

A specialist may take a history, arrange blood tests (including hormones and thyroid), and suggest a pelvic ultrasound to look for causes such as PCOS.

When to see a specialist

If your cycle has changed persistently, or irregular periods come with other symptoms, a review can help identify the cause and options.

Frequently asked questions

Sources & further reading

This page is structured around information from reputable Australian health bodies:

More plain-language reading from Dr Sivadas.

PCOSPCOS diagnosis Menstrual & BleedingAbsent periods MenopauseRecognising perimenopause ContraceptionLong-acting reversible contraception

Written & medically reviewed by

Dr Priya Sivadas

FRANZCOG, CREI, MMed · Fertility and Gynaecology Specialist

Last reviewed: 5 July 2026

Read Dr Sivadas's profile

drpriyasivadas.com.au

Noticed a change in your cycle?

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Consulting locations

Parramatta

Monash IVF

Level 2, 1 Fennell Street
Parramatta NSW 2151

Bella Vista

Norwest Private Hospital

Suite 106, 11 Norbrik Drive
Bella Vista NSW 2153

Penrith

Somerset Specialist Centre

Level 3/38 Somerset St
Penrith NSW 2747