There are many reasons why a woman may miss her period, or why periods might stop altogether.
Most women have a period every 28 days or so, but it's common to have a slightly shorter or longer cycle than this (from 21 to 40 days).
Some women do not always have a regular menstrual cycle. Their period may be early or late, and how long it lasts and how heavy it is may vary each time.
There are a number of reasons why your periods can stop. The most common reasons are:
It might be that your period is simply late, so you could wait a few days to see if it arrives. If it does not arrive, you can do a pregnancy test to confirm whether or not you're pregnant.
It's important to be aware that you can get pregnant in the days after your period is normally due. This can happen if the release of an egg (ovulation) is delayed – for example, as a result of illness or stress.
If you're stressed, your menstrual cycle can become longer or shorter, your periods may stop altogether, or they might become more painful.
If you're finding it hard to cope with stress, cognitive behavioural therapy (CBT) may be recommended. CBT is a talking therapy that can help you manage your problems by changing the way you think and act.
Excessive or sudden weight loss can cause your periods to stop. Severely restricting the amount of calories you eat stops the production of hormones needed for ovulation.
Your GP may refer you to a dietitian if you're underweight, which is when you have a body mass index (BMI) of less than 18.5. A dietitian will be able to advise you about how to regain weight safely.
Being overweight can also affect your menstrual cycle. If you're overweight, your body may produce an excess amount of oestrogen, one of the hormones that regulate the reproductive system in women.
Excess oestrogen can affect how often you have periods, and can also cause your periods to stop.
Your GP may refer you to a dietitian if you're overweight, with a BMI of 30 or more, and it's affecting your periods. The dietitian will be able to advise you about losing weight safely.
The stress that intense physical activity places on your body can affect the hormones responsible for your periods. Losing too much body fat through intense exercise can also stop you ovulating.
You'll be advised to reduce your level of activity if excessive exercise has caused your periods to stop.
If you're a professional athlete, you may benefit from seeing a doctor who specialises in sports medicine. They'll be able to give you advice about how to maintain your performance without disrupting your periods.
You might miss a period every so often if you're taking the contraceptive pill. This is not usually a cause for concern.
However, your periods should return when you stop using these types of contraception.
You may start missing periods as you approach the menopause. This is because oestrogen levels start to decrease, and ovulation becomes less regular. After the menopause, your periods stop completely.
The menopause is a natural part of ageing in women, which usually happens between the ages of 45 and 55. The average age for a woman to reach the menopause is 51 in the UK.
However, around 1 in 100 women go through the menopause before the age of 40. This is known as premature menopause or premature ovarian failure.
Polycystic ovaries contain a large number of harmless follicles, which are underdeveloped sacs in which eggs develop. If you have PCOS, these sacs are often unable to release an egg, which means ovulation does not take place.
PCOS is thought to be very common, affecting about 1 in every 10 women in the UK. The condition is responsible for as many as 1 in 3 cases of stopped periods.
See your GP if you're not pregnant – you've had a negative pregnancy test – and you've missed more than 3 periods in a row.
If you're sexually active and you have not taken a pregnancy test, your GP may advise you to take one.
They may also ask you about:
Your GP may recommend waiting to see whether your periods return on their own. In some cases you may need treatment for your periods to return.
You should also see your GP if your periods stop before you're 45 or if you're still bleeding when you're over 55.
If your GP thinks a medical condition might have caused your periods to stop, they may refer you to a consultant who specialises in the condition.
Depending on what your GP suspects is causing the problem, you may be referred to:
You may have a full gynaecological examination and various tests, including:
If test results show a medical condition has caused your periods to stop, you may be offered treatment for your condition.
For example, if the cause is PCOS, you may be advised to take the contraceptive pill or tablets containing a hormone called progesterone.
Read more about the treatment of PCOS.
If the cause is early menopause (premature ovarian failure), this means the ovaries no longer function normally. Hormone medicine is usually recommended. Treatments may include the contraceptive pill or hormone replacement therapy (HRT).
If you have an overactive thyroid gland, you may be given medication to stop your thyroid producing too many hormones.
Read more about treating an overactive thyroid gland.