Quick answer. Irregular periods are commonly caused by polycystic ovary syndrome (PCOS), thyroid problems, perimenopause or stress. See a doctor if you have very heavy bleeding, bleeding between periods, or any bleeding after menopause.
An occasional change in your cycle is usually normal, but periods that are consistently irregular can point to a hormonal cause such as PCOS, a thyroid problem, perimenopause or significant stress.
This guide explains the common causes, the bleeding patterns that need assessment, and which specialist to see in Singapore.
At a glance
| Possible cause | What it suggests | Urgency |
|---|---|---|
| Polycystic ovary syndrome (PCOS) | Irregular cycles with acne, excess hair or weight gain | See a gynaecologist for assessment |
| Thyroid disorder | Cycle changes with fatigue, weight or temperature changes | See a doctor for thyroid testing |
| Perimenopause | Changing cycles in your 40s, hot flushes | Non-urgent; review if bleeding is heavy |
| Stress, weight change or excess exercise | Cycles affected by lifestyle factors | Non-urgent; see a doctor if persistent |
| Heavy or between-period bleeding | May indicate fibroids, polyps or other conditions | See a doctor; post-menopausal bleeding needs prompt review |
Red flags: when to see a doctor
While many irregular periods are harmless, see a doctor for assessment if you have any of these:
- Very heavy bleeding — soaking through pads or tampons, passing large clots, or bleeding that interferes with daily life.
- Bleeding between periods or after sex.
- Any bleeding after menopause (after your periods have stopped for 12 months) — this always needs to be checked.
- No periods for more than three months when you are not pregnant.
Seek urgent care if heavy bleeding is making you feel faint, dizzy or breathless. In a medical emergency in Singapore, call 995 or go to A&E.
What counts as an irregular period
The average menstrual cycle is around 28 days, though anywhere from about 21 to 35 days can be normal. Periods are considered irregular when the gap between them keeps changing, when they become much heavier or lighter, or when they stop and start unpredictably. Occasional variation is common; a persistent change is what’s worth reviewing.
Common causes of irregular periods
PCOS is a common hormonal condition that causes irregular or absent periods, and may come with acne or excess hair growth. Thyroid disorders can also disrupt cycles. Perimenopause naturally makes periods irregular in the years before menopause. Stress, significant weight change and heavy exercise can all temporarily affect your cycle, as can some forms of hormonal contraception.
How irregular periods are investigated
A doctor will ask about your cycle, symptoms and medical history, and may arrange blood tests to check hormone levels and thyroid function, a pregnancy test, and an ultrasound of the pelvis. Tracking your cycles beforehand can help your doctor identify the pattern and likely cause.
Which specialist should you see?
A GP or polyclinic can do initial tests and refer you if needed. For ongoing irregular periods, heavy bleeding or suspected PCOS, see a gynaecologist for assessment and management.
Browse our directory of gynaecologists in Singapore.
When to seek help sooner rather than later
Don’t ignore very heavy bleeding, bleeding between periods, or any bleeding after menopause — these always deserve a medical review. Early assessment helps identify treatable causes and protects your long-term reproductive health.
How to prepare for your appointment
Tracking your cycle before your visit makes the assessment much easier. Note the dates of your recent periods, how long they last, how heavy they are, and any bleeding between periods or after sex. Record other symptoms such as acne, excess hair growth, weight changes, hot flushes, fatigue or mood changes, as these can point to causes like PCOS, thyroid problems or perimenopause. List your medications and any hormonal contraception, and mention whether you could be pregnant. A simple period-tracking app or diary covering a few cycles is ideal to bring along.
What to expect at the appointment
Your doctor will ask about your cycle, general health and family history, and examine you where appropriate. Common tests include a pregnancy test, blood tests to check hormone and thyroid levels, and a pelvic ultrasound to look at the ovaries and womb lining. The aim is to identify the underlying cause so that treatment can be tailored, whether that is lifestyle support, hormonal treatment to regulate cycles, or further investigation of heavy or unusual bleeding.
Self-management and lifestyle
Some causes of irregular periods respond to lifestyle measures. Maintaining a healthy, stable weight can help regulate cycles, particularly in PCOS, where even modest weight loss may improve symptoms. Regular, moderate exercise and managing stress support hormonal balance, while very intense exercise or significant weight loss can themselves disrupt periods. A balanced diet and good sleep habits are sensible foundations. These steps complement, rather than replace, medical assessment when periods are persistently irregular.
Special situations
Any bleeding after menopause, defined as 12 months with no periods, always needs to be checked, even if it is light. Teenagers often have irregular cycles in the first year or two after periods begin, which is usually normal, but very heavy or absent periods should still be reviewed. In your 40s, changing cycles are commonly due to perimenopause, though heavy or unusual bleeding still deserves assessment.
Common questions
How irregular is too irregular?
Occasional variation is normal. See a doctor if your cycles are persistently unpredictable, you have no period for more than three months without being pregnant, or you have heavy bleeding or bleeding between periods.
Will I need treatment?
Not always. Some causes settle with lifestyle changes or simply need monitoring. Others, such as PCOS or thyroid disorders, benefit from specific treatment, which your doctor can discuss once the cause is clear.
Related guides
- Best Gynaecology Clinics in Singapore — our editorial shortlist
- gynaecology clinics directory
- Frequent urination
- Painful urination
- Pelvic pain
Sources
- KK Women's and Children's Hospital – Menstrual Problems
- SingHealth – Irregular periods may indicate PCOS
- NHS – Irregular periods
- NHS – Endometriosis
Part of our Women’s health & gynaecology guides · Browse all health topics