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Irregular periods - management & treatment

Irregular periods can be a symptom of PCOS. Learn about what an irregular period is and the different ways to manage and treat irregular periods if you have PCOS, including hormonal contraception, such as the oral contraceptive pill, and metformin.

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What are irregular periods?

Although some women with PCOS have regular periods, high levels of androgens (also known as ‘male-type hormones') and too much insulin in their bodies can disrupt the monthly cycle of ovulation and menstruation of many women with PCOS.

If you have PCOS, your periods might be irregular, or stop altogether. The average menstrual cycle is 28 days – with one ovulation when an egg is released – but anywhere between 21 and 35 days is considered normal.

An 'irregular' period cycle is defined as either:

  • eight or fewer menstrual cycles per year
  • menstrual cycles shorter than 21 days
  • menstrual cycles longer than 35 days; or, for young women within three years of starting periods, longer than 45 days.

For adolescents, ‘irregular periods’ means:

  • periods have not started by the age of 15
  • more than a year after periods have started, menstrual cycles are longer than 90 days
  • between one and three years since periods started, cycles are shorter than 21 days or longer than 45 days.

As menstrual cycles lengthen, ovulation can stop entirely (called anovulation) or occur only occasionally. Some women with PCOS also experience heavier or lighter bleeding during their menstrual cycle.

Regular periods help to prevent excess thickening of the lining of the uterus (womb). Not having regular periods can lead to abnormal cells building up inside the womb. It is important you have at least four cycles a year to avoid a build-up that might include abnormal cells. If you have fewer than four periods a year, discuss this with your doctor.


Treatment options


A healthy lifestyle has been shown to be the most effective approach to managing PCOS successfully and reducing the severity of symptoms. A healthy lifestyle includes eating a balanced and nutritious diet, maintaining a healthy weight, being as active as possible, and minimising harmful habits such as smoking and excessive drinking.

Evidence shows that women with PCOS who are overweight can experience significant improvement in their PCOS symptoms when they lose a small amount of excess weight. A weight loss of 5-10% of body weight can improve menstrual regularity.

A dietitian can help you find a diet that works best for you and support you to achieve your long-term goals. For more information on healthy diets, see Food, eating & PCOS.

Changing your lifestyle can be challenging. It is important to know that there is help available to support you in making changes you can maintain. See the pages on Healthy living for more information.

Natural therapies

Over 70% of women with PCOS in Australia use natural and complementary therapies to improve one or more aspects of their health. Get more information on how natural therapies can help manage insulin resistance and menstrual cycles here.

Group girls table smiling pcos booklet

PCOS booklet

Read more on PCOS in our booklet 'Understanding polycystic ovary syndrome: All you need to know'

Hormonal contraception

Some women will need medication and lifestyle changes to make the periods regular. Your doctor can prescribe hormonal contraception for this. These medications include:

  • a combined oral contraceptive pill (‘the pill’)
  • progesterone, which stimulates the uterus and induces bleeding
  • hormonal implants
  • vaginal contraceptive rings
  • intra-uterine devices containing progesterone.

It is important to discuss the options with your doctor and work together to choose the method of hormonal contraception that is right for you.

How they work

The oestrogen and progesterone in hormonal contraception act to override the body’s control of the menstrual cycle and ovulation. The oral contraceptive pill works by ‘switching off the ovaries’. This means that when a woman takes the contraceptive pill, her production of hormones such as testosterone is greatly reduced.

The oral contraceptive pill (‘the pill’) reduces ovarian production of testosterone and other androgens. It also increases the body’s production of sex hormone binding globulin (SHBG). This reduces the activity of testosterone and reduces the symptoms of male-hormone or androgen excess.

Oral contraceptives can worsen insulin resistance and slightly increase the risk of type 2 diabetes in very obese women with PCOS. In general, most oral contraceptives have similar effects on androgen excess.

Possible side effects

Some of the more common side effects associated with hormonal contraceptive medication include:

  • mood changes
  • weight gain or loss
  • bloating
  • breast tenderness
  • irregular bleeding.

These side effects can differ, depending on the oestrogen and progesterone content of the pill or device.

Potential risks

The oral contraceptive pill should be used with care if you have high blood pressure, are extremely overweight or are a smoker. Usually the oral contraceptive pill would not be recommended if you have had a deep vein thrombosis (DVT) or other thrombosis in the past. Low-dose preparations appear to work equally as well as larger doses.

There is some recent evidence to suggest hormonal contraception might increase insulin resistance, abnormal glucose tolerance (a sign of early diabetes) and cholesterol levels (triglycerides). Low-dose preparations appear to be better (such as 20µg oestrogen pills).

However, other evidence shows no negative effects of the oral contraceptive pill on risk factors for type 2 diabetes and cardiovascular disease.

Any woman considering use of the oral contraceptive pill should discuss the benefits and risks, given their individual circumstances and health, with their doctor.

The contraceptive pill


Metformin is used to treat insulin resistance and diabetes by improving the sensitivity of insulin and by reducing glucose production by the liver. Metformin has a number of effects within the body, but of primary relevance to women with PCOS is that it reduces insulin resistance and the production of androgens, or testosterone, in the ovaries. This can improve the function of the ovary and re-establish regular periods (menstruation).

Metformin does not appear to be quite as effective as the oral contraceptive pill in improving menstrual regularity and reducing androgen excess. It has a more positive effect on cholesterol levels and insulin than the oral contraceptive pill. It also assists in weight loss and prevention of weight gain, and reduces the risk of diabetes in those at high risk.

Possible side effects

Metformin has been in use for around 60 years and is a drug with few serious side effects, except for in the elderly or those with liver or kidney failure. Some women who take metformin have some temporary gastrointestinal side effects (nausea, abdominal bloating, vomiting and loss of appetite).

Metformin treatment can be started at lower doses to reduce the severity of these side effects. The slow-release form of metformin, taken at night, has less severe side effects than standard metformin treatment.

Taking actions

To decide on the best therapy for you to help with irregular periods, discuss your options with your doctor. Prioritise what is most important to you and communicate this with your doctor.

A healthy lifestyle is one of the most important aspects of managing PCOS successfully. Loss of excess weight can reduce the severity of some symptoms. A 5-10% weight loss can have significant health benefits, including more regular menstrual cycles, improved mood and fertility, and a reduced risk of diabetes.

0919 jh factsheet pcos THUMB

PCOS fact sheet

Includes information on how to improve PCOS symptoms and manage your long-term health.

This web page is designed to be informative and educational. It is not intended to provide specific medical advice or replace advice from your health practitioner. The information above is based on current medical knowledge, evidence and practice as at September 2019.


Last updated: 27 April 2021 | Last reviewed: 01 September 2019

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