Irregular Periods: What They Mean and How to Manage Them

A menstrual cycle that is shorter than 21 days or longer than 35 days can be considered irregular. This means the time from when you start your period (day 1 of your cycle) to the day before your next period (the last day of your current menstrual cycle). Some people may get a heavier or lighter flow, or their cycle length may vary by more than 9 days.

Most people usually have a period that lasts between 4 and 7 days. Your period typically occurs every 28 days. However, this is just an average, and a normal cycle length can range from 21 to 35 days.

There are many causes of irregular periods, from stress and exercise to more serious underlying health conditions. Common causes of irregular periods include:

Hormone imbalances

Oestrogen and progesterone imbalances can cause irregular periods. For example, excess oestrogen levels can cause heavy periods, while low progesterone levels may result in irregular cycles.

Lots of things can cause hormonal imbalances, including certain health conditions or medications, and stress. These are also discussed in more detail on this page.

Stress

Stress can cause irregular periods because it can disrupt the hormones produced by the hypothalamus, an area of the brain responsible for regulating hormones, including those that control menstruation. Typically, chronic stress can lead to irregular menstrual cycle lengths and changes in menstrual flow.

Exercising too much

Although exercise is good for you, vigorous or excessive exercise can harm your health and affect menstruation. Strenuous exercise can disrupt the hormones that regulate the menstrual cycle, causing missed, irregular, or absent periods.

Up to 80% of people who have periods that exercise vigorously experience some form of menstrual dysfunction. However, moderate exercise is beneficial for your overall health, including reproductive health.

Here’s how to do it safely: Exercising during your period.

Sudden weight changes

Both sudden weight loss and weight gain can impact your periods because of the hormonal imbalances that can occur with weight fluctuations.

Pregnancy

A missed or late period is usually an early sign that you are pregnant. Pregnancy prevents periods because the process that triggers menstruation is temporarily stopped to support the developing foetus.

Medications and contraception

Some medications can affect the menstrual cycle, such as:

• blood thinners
• antidepressants
• thyroid medications
• epilepsy medications
• hormonal contraception

Hormonal contraception, like the contraceptive pill, can make periods lighter and less frequent, or stop them completely. If you’re worried that any medication you are taking is affecting your periods unintentionally, you should tell your doctor.

Polycystic ovary syndrome (PCOS)

Irregular periods are one of the most common signs of PCOS, with 75 to 85% of people experiencing menstrual dysfunction. High levels of circulating male hormones (androgens) can stop ovulation or make it infrequent, which can result in irregular periods.

Thyroid issues

Both an underactive (hypothyroidism) and an overactive thyroid (hyperthyroidism) can disrupt the menstrual cycle, causing symptoms like:

• period flow changes
• irregular periods
• absent periods

Thyroid issues can also impact ovulation, making it more difficult to get pregnant.

Perimenopause

Perimenopause is the stage of life leading up to menopause and usually starts during your 40s. During this time, your menstrual cycle may become shorter, and your periods may become longer or shorter due to declining hormone levels.

Some of the common signs of an irregular menstrual cycle include:

• periods that are fewer than 21 days or more than 35 days apart
• missing 3 or more periods in a row
• heavy or lighter periods than usual
• periods that last longer than 7 days
• the length of time between cycles varies by more than 9 days
• bleeding between periods
• severe pain or cramping

Although irregular periods are common and typically not a cause for concern, they can sometimes be a sign of an underlying health issue. There are many potential causes of an irregular menstrual cycle, from stress to menopause, but you should speak to a doctor if:

• your period is usually regular, but suddenly becomes irregular
• you have missed 2 or 3 periods, and you are not pregnant
• you’re bleeding between periods or after sex
• you have heavy periods, or they last more than 7 days
• your cycle dramatically varies in length
• you are getting vaginal bleeding after menopause
• you’re getting additional symptoms such as unusual vaginal discharge or a fever, as these could be signs of a sexually transmitted infection (STI)

If you have recently had unprotected sex and your period is late, you could be pregnant, so you should take a pregnancy test.

How are irregular periods diagnosed?

A doctor or nurse can diagnose irregular periods through a combination of discussing your medical history, physical examinations, and blood tests.

Before seeking a diagnosis, it can be helpful to keep track of your periods using an app or diary, noting the day your period starts, any symptoms you experience, and any bleeding between periods.

If a hormone imbalance is causing your irregular menstrual cycle, your doctor may arrange tests that can pick up things like PCOS or menopause.

If you’re getting other symptoms, such as a fever or abnormal discharge, you may need an STI test

Treatment options for irregular periods will depend on the cause but can include hormone replacement therapy, hormonal birth control, or addressing underlying health conditions. However, treatment is not always needed for irregular periods, and some people respond well to lifestyle changes, such as exercise and stress management.

If the cause of irregular periods is not obvious, your doctor may refer you to a gynaecologist for a diagnosis.

Lifestyle changes

Because factors such as stress and vigorous exercise can disrupt your menstrual cycle, making small lifestyle changes can have a significant impact. Some of the things you can try include:

Stress management

If you have been under a lot of stress recently and have noticed changes to your periods, practising stress management techniques can help. You can try activities like:

• yoga
• meditation
• breathing exercises
• therapy

Several studies have investigated the effect of yoga on menstrual cycle irregularities. One study found that yoga is an effective way to reduce menstrual pain in women with absent periods, and another study found yoga helped with various menstrual issues, including helping to regulate them too.

Diet changes

Diet can significantly impact your menstrual cycle. It’s essential to eat enough food and get the right combinations of nutrients to maintain balanced hormones.

To help regulate your period, here are some diet do’s and don’ts:

Tracking your periods can help diagnose underlying health conditions or, if you are trying to get pregnant, calculate your fertile window. However, keeping track of your periods when they are irregular can be challenging, but there are several things you can do, such as:

The calendar method

The calendar method may not be the most reliable method to use if you have irregular periods, but it can help start a conversation with your doctor about your cycle length and symptoms. Keep track of the day your period starts each month, and write down how you're feeling or any symptoms you’re experiencing, including the appearance of your vaginal discharge.

Period tracking apps

Period tracking apps work similarly to the pen-and-paper method. They can help you track your cycle and spot changes or patterns. You can also usually record any test results, such as ovulation tests, in them, as well as any symptoms you are experiencing.

How do you know when you're ovulating if you have irregular periods?

Tracking ovulation can be difficult if you have irregular menstrual cycles, but there are several things you can do to find out if you are ovulating and when.

Ovulation tests

Ovulation tests work by tracking your luteinising hormone (LH) level, which surges just before an egg is released from your ovaries. Usually, you should start testing 4 days before you are expecting to ovulate, but if you are not sure, you should do daily tests to avoid missing the LH surge if you are trying to get pregnant.

Cervical mucus

Checking your cervical mucus can also help you track ovulation. Just before you ovulate, vaginal discharge becomes clear and slippery, like an egg white consistency, to help sperm meet and fertilise an egg.

Basal body temperature

Measuring your basal body temperature (BBT) can also help you predict when ovulation may occur. Your BBT rises very slightly around ovulation, but it’s also a sign that it has already occurred. However, you can use this information to confirm that an ovulatory cycle has occurred.