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What could cause my periods to
become irregular or heavy?
Changes in your periods can be common during the reproductive years but significant changes in your usual pattern are worth understanding.
Periods may become irregular, more frequent, longer or heavier for many different reasons.
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Sometimes these changes are related to hormonal or ovulation changes while other causes can involve the uterus, thyroid, medications or underlying conditions.
Understanding what is normal for you can help identify when further assessment may be appropriate.
What is a normal menstrual cycle?
A menstrual cycle can vary between individuals and may change over time. For most women, periods occur regularly enough to form a recognisable pattern, although the timing and amount of bleeding can vary.
A change from your usual pattern is often more important than a particular cycle length on its own.
Why can periods become irregular?
Irregular periods can occur when ovulation does not happen regularly. Hormonal changes, significant changes in weight, stress, some medications and conditions affecting the thyroid or ovaries can all influence the menstrual cycle.
PMOS is another possible cause, particularly when irregular periods occur alongside symptoms such as acne, increased facial or body hair or scalp hair thinning.
What makes a period unusually heavy?
Heavy menstrual bleeding means losing more blood than is usual for you or bleeding enough to interfere with everyday activities.
You may notice that you need to change pads or tampons very frequently, bleed through clothing or bedding, pass large clots or bleed for longer than a week.
Heavy bleeding can also lead to iron deficiency and tiredness.
Could there be an underlying condition?
Heavy or irregular bleeding can sometimes be associated with conditions affecting the uterus such as fibroids or adenomyosis. Endometriosis, thyroid problems, bleeding disorders and some medications can also contribute.
Sometimes no specific cause is found. The important consideration is whether the change is new, persistent or affecting your health and daily life.
When to see a doctor
If your periods have become noticeably heavier, more irregular or different from your usual pattern it is worth discussing this with your doctor.
Assessment may include questions about your cycle, symptoms and medical history and, when appropriate, blood tests or an ultrasound to investigate possible causes.
Key points
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Periods can vary naturally but significant changes from your usual pattern deserve attention.
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Irregular periods may be related to changes in ovulation or underlying hormonal conditions.
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Heavy bleeding can have several causes including fibroids, adenomyosis and bleeding disorders.
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Heavy periods can lead to iron deficiency and anaemia.
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Persistent or troublesome changes should be assessed by a healthcare professional.
Medically reviewed by Dr Susana Rodriguez, menopause clinician at ClaraSana Women’s Health, Perth.
Our content is based on up-to-date Australian guidelines & may differ from information on other sites.