Irregular periods: what is normal and when to see a gynaecologist

What counts as irregular?

Every woman's cycle is a little different. Doctors usually describe a cycle as irregular when the gap between periods is shorter than 21 days or longer than 35 days, when the length changes a lot from month to month, or when periods stop altogether.

Cycles are often irregular in the first few years after periods start and again in the years before menopause. That is usually normal, but it is still worth checking if bleeding is heavy or you feel unwell.

Common causes

Many causes are simple and short-lived. Others need treatment, so a check-up is worthwhile if the change lasts.

• Polycystic ovary syndrome (PCOS), often with acne, weight gain or extra hair growth
• Thyroid problems, either an underactive or overactive thyroid
• Stress, poor sleep, sudden weight loss or gain, or heavy exercise
• High prolactin, a hormone that can also cause milky nipple discharge
• Fibroids, adenomyosis or polyps in the womb, which tend to cause heavy or prolonged bleeding
• Endometriosis, which often makes periods painful
• Pregnancy and breastfeeding, and some contraceptives
• Less often, cancer of the cervix, ovary or the lining of the womb (endometrium). This is why changes that persist should be checked

When to see a gynaecologist

Book a consultation if any of these apply. Most causes are easy to identify and treat.

• Periods have been irregular for three months or more
• No period for 90 days and a pregnancy test is negative
• Very heavy bleeding, soaking a pad every hour or passing large clots
• Bleeding between periods, after sex or after menopause
• Periods that come with pain
• You are trying to get pregnant

Tests your doctor may suggest

The gynaecologist will ask about your cycle, weight changes, medicines and any plans for pregnancy, then examine you. Common tests are a pregnancy test, blood tests for thyroid, prolactin and other hormones, a blood count to check for anaemia, and a pelvic ultrasound to look at the womb and ovaries.

Treatment depends on the cause. It may be lifestyle changes, medicines to regulate the cycle, treatment of a thyroid problem, or a minor procedure for fibroids or polyps.