Irregular periods

A period, medically called menstruation, occurs when the lining of your womb is shed as part of your natural menstrual cycle. Shedding is seen as bleeding from your womb that passes out of your vagina. On average, periods happen once a month and start during puberty between ages 10–16. 

After puberty, most women develop a regular menstrual cycle with roughly the same gap of time between one period and the next. However, it is normal for this gap to vary by a few days between each period. Periods continue until menopause which usually starts between age 45–55. 

Irregular periods, medically called oligomenorrhea, happen when the gap of time between your periods keeps changing. Your periods may therefore come early or late. In some cases, it could be a sign that you have a health issue or medical condition that can be treated.

Irregular periods can occur if you:

• Are experiencing hormonal changes in the run-up to menopause
• Are performing endurance exercises
• Change the type of contraception you use
• Have a hormone imbalance

If you are experiencing puberty or menopause, you will not usually need treatment for your irregular periods. However, if you have irregular periods during your reproductive years (the years between puberty and menopause), you may need to see your GP.

On average, periods happen every 28 days and last for about five days. However, it's common for the time between periods to be longer or shorter than this or to last longer than seven days. Most women have 11–13 periods each year. You shouldn’t worry if:

• You're still going through puberty — it can take up to two years for your periods to settle into a regular cycle
• You've always had slightly irregular periods of a few days

You probably have irregular periods if:

• The blood you pass during your period contains clots that are more than 2.5cm in diameter
• The length of time between your periods keeps changing
• The variation in time between your periods is seven days or more
• There are changes in the amount of blood flow from one period to the next
• Your menstrual cycle is longer than 35 days 

Irregular periods can be caused by a variety of reasons, many of which involve hormonal changes. The two main hormones that regulate your menstrual cycle are oestrogen and progesterone. These hormones are affected by natural changes in your body during your lifetime which can cause irregular periods. These changes include puberty, menopause, pregnancy, childbirth and breastfeeding.

Periods start during puberty but it can take up to two years for oestrogen and progesterone levels to settle and ensure regular periods. Irregular periods are also common before menopause, with the amount of blood loss varying from one period to the next. 

During pregnancy, menstruation stops although you may still experience some bleeding early in pregnancy. Most women do not have periods during the months they are breastfeeding.

Other reasons for irregular periods include:

• Being overweight
• Being stressed
• Eating disorders that cause extreme weight gain or weight loss eg anorexia
• Performing endurance exercises eg marathon running
• The contraceptive pill or intrauterine system (IUS) — the contraceptive pill can cause spotting (small amounts of blood loss) in between periods and an IUS can cause heavy bleeding during your period

Irregular periods could also be a sign of an underlying medical condition such as:

• Endometriosis — cells lining the womb grow outside the womb, which can cause no symptoms but can also cause infertility, irregular periods and pain; the abnormal growth of cells is not cancerous but often causes symptoms as these cells are normally shed during a period
• Pelvic inflammatory disease (PID) — the most common complication of a sexually transmitted infection (STI) in women, which causes the fallopian tubes, ovaries and/or womb to become infected and if left untreated can damage the fallopian tubes and womb, causing long-term pain; symptoms include bleeding in between periods and after sex; if diagnosed early PID can be treated with antibiotics
• Polycystic ovary syndrome (PCOS) — the development of multiple small, fluid-filled sacs (cysts) in the ovaries that prevent an egg being released each month (ovulation); women with PCOS often have higher than normal male sex hormones and symptoms including: 
• Acne
• Being overweight
• Excess hair growth
• Irregular or no periods
• Thyroid problems — your thyroid gland makes hormones that affect your metabolism and problems with your thyroid gland can cause heavy, irregular or absent periods

In rare cases, irregular periods may be a sign of cancer of the womb or the neck of the womb (cervix). These cancers can cause bleeding in between periods or during sex.

Keep a note of when your periods start, then count the days between them, to see if this varies. 

Irregular periods aren't always a sign of a medical problem but it's a good idea to visit your GP to rule out or identify possible health issues, especially if:

• The difference between your shortest and longest menstrual cycle is 20 days or more
• You have irregular periods and are finding it hard to get pregnant
• You have periods more often than every 21 days or less often than every 35 days
• Your periods last longer than seven days
• You're under 45 and your periods suddenly become irregular

Also, tell your GP if you have heavy irregular periods, are bleeding between periods or have symptoms such as pain or discomfort.

In order to make a diagnosis, your GP may:

• Arrange a blood test to check your hormone levels
• Ask if you might be pregnant
• Assess your stress levels
• Measure your blood pressure and weight
• Perform an internal examination
• Send you for an ultrasound scan of your womb 

You may be referred to a gynaecologist if your doctor feels you need further tests or specialist treatment.

If you have irregular periods, it can be harder to become pregnant as you may not regularly release an egg. Your chances of conceiving may be better if you have sex every two or three days throughout your menstrual cycle — you do not need to time sex around ovulation.

If you are experiencing puberty or menopause, you will not usually need treatment for your irregular periods. Treatments for irregular periods depend on the underlying cause of the problem. 

If the cause is the contraceptive method you're using and your irregular periods continue for several months, your GP can suggest alternative contraceptive methods. 

If you’re overweight or obese, including if you’re overweight and have PCOS, losing excess weight can help. This reduces the amount of insulin your body produces, which reduces your testosterone levels — this increases your chances of ovulating regularly.

If you have thyroid problems, you will receive specific treatment for the underlying problem, which will also help your periods become more regular. Treatments for thyroid problems include medication, radioactive iodine therapy and surgery.

If stress or eating disorders are causing your irregular periods, psychological therapy may help, including relaxation techniques, stress management and talking to a therapist.

For hormonal causes of irregular periods, your doctor may recommend hormone therapy, such as: 

• A low-dose contraceptive pill containing oestrogen and progesterone
• Taking progesterone for 10—14 days every month 

Metformin is also a treatment for irregular periods. This medication is used to treat type 2 diabetes and causes insulin levels to decrease, which reduces testosterone levels and therefore increases your chances of ovulating regularly. 

Getting pregnant can be difficult for some women with irregular periods, but hormone or fertility treatments can help.

Lifestyle changes can also help your periods become more regular, such as exercising regularly to maintain a healthy weight and reduce your stress levels, and eating a balanced, healthy diet.