Irregular periods — when to worry

Almost every woman has an unpredictable cycle at some point. Stress, travel, illness and weight changes all shift things temporarily. The useful question isn't "was this month odd?" but "has this become a pattern?"

What counts as normal

A typical cycle runs 21 to 35 days from the first day of one period to the first day of the next, with bleeding lasting two to seven days. Cycles vary by a few days month to month, and that's fine.

It's considered irregular when cycles are consistently shorter than 21 days or longer than 35, when the gap varies widely from month to month, or when periods stop for three months or more without pregnancy.

The first couple of years after periods begin, and the years approaching menopause, are naturally irregular — that's expected, not a problem.

Common causes

• PCOS — the single most common cause of persistently long cycles in younger women
• Thyroid disorders — both underactive and overactive thyroid disrupt cycles, and both are easily tested for
• Raised prolactin — can stop periods altogether
• Significant weight change, in either direction
• Intense exercise or very low body fat
• Stress and disrupted sleep
• Fibroids or polyps — more often cause heavy bleeding than irregular timing
• Perimenopause — usually from the mid-forties
• Contraception — hormonal methods commonly change bleeding patterns, often harmlessly

Patterns that need review

Book an appointment rather than waiting if you notice:

• Bleeding between periods, or after intercourse
• Periods so heavy you soak through protection hourly, or pass large clots
• No period for three months or more, with a negative pregnancy test
• Cycles that have become consistently shorter than 21 days
• Any bleeding after menopause — this always needs prompt assessment
• Severe pain that stops you working or sleeping
• Irregular cycles alongside acne, excess hair growth or difficulty conceiving

What an assessment involves

Usually a conversation about your cycle history, an examination, a pelvic ultrasound, and blood tests — thyroid function, prolactin, and hormone levels depending on the picture. A pregnancy test comes first regardless, because it changes everything that follows.

Keeping a simple record of your last few cycles — start date and how many days of bleeding — makes that first consultation far more productive than trying to recall it on the spot.

How it's treated

Treatment addresses the cause rather than the symptom. Thyroid problems are corrected with medication and cycles usually follow. PCOS is managed with lifestyle change and, where appropriate, hormonal treatment. Fibroids and polyps may need a procedure if they're causing heavy bleeding.

Where no specific cause is found and the pattern is troublesome, hormonal treatment can regulate cycles effectively. The point of investigating first is to make sure you're treating the right thing.