Your menstrual cycle can be disturbed if you change your method of contraception or if you have an imbalance of the hormones oestrogen and progesterone.
It is not unusual to have a hormone imbalance for a few years after puberty and before the menopause. This can cause your menstrual cycle to become longer or shorter. Your periods may also become lighter or heavier.
If your irregular periods are caused by these age-related factors, you will usually not need to see your GP.
Lifestyle factors
The following lifestyle factors can also upset your balance of hormones and cause irregular bleeding:
- extreme weight loss or weight gain
- excessive exercise
- stress
Contraceptives
An intrauterine device (IUD) or contraceptive pill may cause spotting between periods. An IUD can also cause heavy bleeding.
Small bleeds, known as breakthrough bleeds, are common when the contraceptive pill is first used. They are normally lighter and shorter than normal periods, and usually stop within the first few months.
Polycystic ovary syndrome
Polycystic ovary syndrome (PCOS) occurs when very small cysts (small, fluid-filled sacs) develop in the ovaries.
The usual symptoms of PCOS are irregular or light periods, or no periods at all. This is because, in women with PCOS, ovulation (the release of an egg) may not take place as often as normal. Also, the production of hormones may be unbalanced, and you could have higher levels of testosterone than normal (this is a male hormone that women normally have a small amount of).
For more information, go to the A-Z topic on polycystic ovary syndrome.
Gynaecological problems
Irregular bleeding can also be due to unsuspected pregnancy (see box), early miscarriage or problems with the womb or ovaries. Your GP may refer you to a gynaecologist (specialist in diseases of the female reproductive system) if further investigation and treatment is needed.
Thyroid disorders
A thyroid disorder is another possible but rare cause of irregular periods (the thyroid gland, found in the neck, produces hormones that maintain the body's metabolism). Your GP may test for a thyroid problem by taking a blood test to check the levels of thyroid hormones in your blood. For more information, go to the A-Z topic on overactive thyroid.
