About this symptom
A typical cycle is about 28 days, counted from the first day of one period to the first day of the next, but it can be a little shorter or longer. Periods are usually called irregular if the gap is under 21 days or over 35 days.
Irregular periods are common and often harmless. They are expected around puberty and in the years before menopause. Stress, big changes in weight, hard exercise, breastfeeding and hormonal contraception can all upset the cycle, and so can hormone problems such as PCOS and thyroid disease. A missed period is also often an early sign of pregnancy.
Possible causes
This is not a diagnosis. These are the causes doctors think about, with the ones that are most urgent to rule out first.
- PregnancyA missed period is often an early sign, and pregnancy is the first thing to rule out. A pregnancy test will tell you.
- Ectopic pregnancyA pregnancy outside the womb. A missed period with pain low in the tummy on one side, vaginal bleeding or brown watery discharge, or pain at the tip of the shoulder. It can be an emergency.Read about it
- PCOSIrregular periods, often with weight gain, tiredness, facial hair, or dry or oily skin. The combined pill may help make periods regular.Read about it
- Underactive thyroidThyroid problems, with too little thyroid hormone or too much (overactive thyroid), can make periods irregular. A blood test checks it, and medicines can treat it.Read about it
- Stress, weight change or too much exerciseStress and anxiety, sudden weight loss or gain, and very hard exercise can all upset the cycle. Periods often settle when the cause is dealt with.
- Hormonal contraceptionThe progestogen-only pill, the contraceptive injection and a hormone coil can change or stop periods. Periods can take months to return after stopping some of them.
- MenopauseIn the years before periods stop (perimenopause), usually between 45 and 55, periods become irregular.Read about it
- BreastfeedingPeriods may be absent or irregular while breastfeeding, a natural cause of missed periods.
When to get help
Also get emergency care for:
- Bleeding that soaks through a pad or tampon every hour for 2 to 3 hours, or that makes you weak or light-headed
- Vaginal bleeding when you are, or could be, pregnant
See a doctor soon if you have:
- Periods that stay irregular, or are under 21 days or over 35 days apart
- Periods that last longer than 7 days, or bleeding between periods
- Missed periods when you are not pregnant
- Periods that have not started by the age of 15
- Irregular periods with weight gain, tiredness, facial hair or dry or oily skin
- Irregular periods and trouble getting pregnant
An occasional late or early period with an ordinary cause, such as stress, and none of these signs can wait.
What you can do at home
Home care cannot treat the cause, but it helps you and your doctor find it.
Do
- If you could be pregnant, take a pregnancy test
- Note the first day of each period and how long it lasts
- Aim for a healthy weight, and avoid crash dieting and very hard exercise
- Find ways to manage stress
Do not
- Do not take hormone tablets or tablets to bring on a period without a doctor's advice
- Do not assume a missed period is stress if you could be pregnant
- Do not ignore severe pain or heavy bleeding
What the doctor will do
The doctor will ask about your cycle, the date of your last period, pregnancy or breastfeeding, contraception, medicines, weight changes, exercise and stress. They will examine you, and do a pregnancy test if there is any chance of pregnancy.
Tests depend on the likely cause. They may include:
- Blood tests for hormones, including thyroid hormone
- A pelvic scan
- A sample from the lining of the womb, only when it is needed
Treatment depends on the cause and is not always needed. For example, the combined pill may help in PCOS, and medicines can treat thyroid problems. You may be referred to a gynaecologist or a hormone specialist.
Myths and facts
Things people often say about this. Open each one to see what is true.
Myth“Irregular periods are normal, so there is no need to see a doctor.”What is true?
Fact
They can be normal at times, for example around puberty and before menopause. But periods that stay irregular can be linked to PCOS or thyroid problems, which can be treated, so see a doctor if they do not settle.
Myth“Taking a tablet to bring on a period is harmless.”What is true?
Fact
A missed period can mean pregnancy, including an ectopic pregnancy, which can be dangerous. The cause should be found first, and hormone tablets should be taken only on a doctor's advice.
Myth“Irregular periods mean you will never get pregnant.”What is true?
Fact
Irregular periods can make pregnancy harder, because you may not release an egg regularly. But the cause can often be treated, and fertility help is available. See a doctor if you are struggling to get pregnant.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
When should I see a doctor about irregular periods?
See a doctor if your periods stay irregular, last longer than 7 days, or come with bleeding between periods, weight gain, tiredness or extra facial hair. Also see one if your periods have not started by 15, or you are struggling to get pregnant.
Can stress make my period late?
Yes. Stress and anxiety, big weight changes and very hard exercise can all make periods late or irregular. But if you could be pregnant, take a pregnancy test first rather than assuming it is stress.
Are irregular periods normal as I get closer to menopause?
Yes. In the years before periods stop, called perimenopause and usually between 45 and 55, periods often become irregular. If they are causing problems, treatment such as hormone replacement therapy may help, so ask a doctor.
Can irregular periods affect getting pregnant?
They can make it harder, because you may not release an egg regularly. If you are struggling to get pregnant, a doctor can look for the cause and arrange tests. Hormone medicines or fertility treatment may be advised.