It’s not uncommon for your menstrual cycle to become disturbed at any point, either during or after puberty and before the menopause. Each person is different, too, so what might be regular for you could be irregular for another – the monthly menstrual cycle typically occurs every 28 days and can last three to seven days. It’s always advisable to see your GP if you suspect anything’s wrong or if you have any reoccurring or problematic symptoms.

Irregular periods can be light, heavy, painful or absent altogether, and can be caused by several underlying factors, including:


Some birth control pills use a combination of oestrogen and progestin to prevent ovulation. When you start a new birth control pill it can take several months for your body to adjust to the dose of hormones you’re getting from the pill. Small bleeds, known as breakthrough bleeds, are common when the contraceptive pill is taken for the first time. They’re usually light and short and should stop within the first few months of taking the pill.

IUDs (intrauterine devices) don’t cause irregular periods, but they can cause heavy or painful bleeding.

Significant weight gain or weight loss

Significant changes in weight (gain or loss) can create a hormone imbalance, which impacts your body’s ability to ovulate. In order for a woman to maintain a regular cycle, her body fat percentage should be at least 17-22%.


Your body needs the energy to menstruate, so if you’re burning too much energy at the gym then your body has no energy left for that time of the month. Excessive exercising reduces the amount of body fat, causing an imbalance in hormones, which contributes to irregular periods.

Increased stress/anxiety

Stress has a direct impact on how much oestrogen and progesterone your body produces. Emotional or physical stress suppresses the functioning of the hypothalamus, which controls the pituitary gland, in turn controlling the thyroid and adrenal glands and the ovaries.  

PCOS (polycystic ovary syndrome)

Women with PCOS usually have a high level of male hormones (androgens) which can disrupt the monthly cycle of ovulation and menstruation. The usual symptoms of PCOS are irregular or light periods or no periods at all.

Thyroid problems

Irregular periods can be a sign of hyper- or hypothyroidism. If your period becomes more frequent and lighter, it can be a sign of hypothyroidism (underactive thyroid). Less frequent and heavier periods are a symptom of hyperthyroidism (overactive thyroid). Thyroid disease is common in women between the ages of 20-30, so if your cycle is irregular during this time, then it could be a sign of thyroid problems. If you suspect you have a thyroid problem, consider booking an appointment with your GP, who may take a few blood tests to check the levels of thyroid hormones in your blood.

Other common causes of irregular periods include smoking, travel, breastfeeding and some cancers and cancer treatment such as chemotherapy and radiation therapy.

If you’ve skipped a period, try not to worry too much. If you suspect you have an underlying problem that could be the cause of your irregular periods, or you have any reoccurring symptoms, then we advise you see your GP as soon as possible.


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Mr Andrew Drakeley Andrew Drakeley

Mr Andrew Drakeley is the Clinical Director at the Hewitt Fertility Centre, working principally at the Liverpool Women’s site but with managerial responsibility for Knutsford.

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