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.

Ectopic

Ectopic refers to a pregnancy that occurs outside of the womb, most commonly in the fallopian tubes.

Ovaries

Ovaries are the pair of reproductive organs that produce eggs and sex hormones in females.

Thyroid

The thyroid is a jointed piece of cartilage that encloses the vocal cords and forms the ‘Adam’s apple’ in men.

Thyroid gland

The thyroid gland in the throat makes hormones to help control growth and metabolism (the process that turns the food we eat into energy).

Womb

The uterus (also known as the womb) is a hollow, pear-shaped organ in a woman where a baby grows during pregnancy.

Irregular periods are common during puberty or just before the menopause and in these cases treatment is usually not necessary.

But if you're worried because your periods are particularly heavy, last a long time or are more frequent than monthly, or if you get bleeding or spotting between periods or after sex, see your GP. Read the box on this page for more specific advice on when you should see your GP.

Your GP will ask questions about your periods, your lifestyle and your medical history to find out the underlying reason for your irregular cycle.

Any treatment that is necessary will depend on the reason for your irregular periods.

Changing your method of contraception

If you have recently been fitted with an intrauterine device (IUD) and you are experiencing irregular bleeding that does not settle within a few months, discuss changing to another method of contraception with your GP or practice nurse.

If you have started taking a new contraceptive pill that is causing irregular bleeding, you may be advised to change to another type of pill.

Treating polycystic ovary syndrome

For overweight women with polycystic ovary syndrome (PCOS), the symptoms can be improved by losing weight, which will also help with irregular periods. By losing weight, your body does not need to produce as much insulin, which reduces testosterone levels and improves your chance of ovulation (releasing an egg each month).

Other treatments for PCOS include hormone treatment and diabetes medication. For more information, see Treating polycystic ovary syndrome.

Treating an overactive thyroid

Treatment for an overactive thyroid aims to return the level of thyroid hormones in your blood to normal. You may need to take medication to stop your thyroid gland producing too many hormones. See Treating hyperthyroidism for more information on this and other treatments. 

Your menstrual cycle should return to normal after your overactive thyroid is treated. If it does not, go back to your GP.

Counselling and stress management

Stress or sudden weight loss may be diagnosed as a cause of irregular periods. Relaxation techniques, stress management or counselling (talking to a therapist) may be recommended.

Counselling

Counselling is guided discussion with an independent trained person, to help you find your own answers to a problem or issue.

Thyroid

The thyroid is a jointed piece or cartilage that encloses the vocal cords and forms the ‘Adam’s apple’ in men.

Thyroid gland

The thyroid gland in the throat makes hormones to help control growth and metabolism (the process that turns the food we eat into energy).