Irregular periods

Why are your periods irregular?

An introduction to irregular periods

It is perfectly normal not to have the same length cycle as your best friend – we are all unique! Your average period comes every 28 days... but if that was a hard and fast rule very few of us would be normal! Most women have a period between every 21 and 36 days and in reality up to 30% of you have irregular periods.

But what exactly makes a period irregular? So the length is one factor, some women have much shorter cycles which mean they get a period more regularly (often these are associated with heavy, painful periods) then others that have a longer cycle. Having a longer cycle can mean that they get their period less often; this is often associated with lighter periods.

Month to month it is common for your cycle to vary slightly too, even if you generally have a longer cycle, your period might not always fall on the exact day its meant to or it might be missed all together! You might get spotting in between periods too!

Many of these symptoms are quite normal and we explain why.

Types of irregular periods

There are different types of irregular periods as we describe below:

  • Polymenorrhoea – is when you have a period cycle every 21 days or sooner. It is often the case that your periods are heavier and more painful in polymenorrhoea
  • Oligomenorrhoea – is when you have periods every 36 days or even further apart, but you still have 4 to 9 periods per year
  • Metrorrhagia – is when you have bleeding in between your periods, although this is often hard to distinguish from an actual period, but typically lasts for two days or less
  • Amenorrhoea – is the complete absence of a period. Again this might be hard to distinguish from oligomenorrhea but generally, if you miss more than three periods in a row or have less than four periods per year, this is classed as amenorrhea.


There are various symptoms to look out which can help you determine whether or not you have irregular periods.

  • Shorter or longer cycles – A period cycle is the length of time from the first day of your period from one month to the next. Generally if this is 21 days or less (polymenorrhoea) or 36 days or more (oligomenorrhoea) you are considered to have irregular periods. 
  • Irregular cycles – You might find the length of your cycles are irregular month to month, so one month you have a period after 37 days then the next one doesn’t come for 42 days
  • The length of you period – On average periods generally last for 3-5 days. Less than 2 days or more than 7 days is classes as an irregular period
  • How heavy they are – Irregular periods are often abnormally heavy or light. See our heavy periods page for more information
  • Missed altogether – It is often hard to distinguish between irregular periods if you have a very long cycle, and a missed period. Generally if you go through three cycles (approximately 84 days) without having a period or have less than 4 a year, you are missing periods.


There is a long list of possible causes of irregular periods. Some common examples are as follows:

  • Hormone imbalance – A hormone imbalance is perhaps the most common cause of irregular periods. See more on our ‘Understanding you period and hormone imbalance’ blog to learn more about what hormones are involved in your menstrual cycle and what parts they have to play. High levels of oestrogen can causes shorter cycles and heavier bleeds whereas high levels of progesterone are more commonly associated with longer cycles and lighter periods
  • Contraception methods – If you have recently switched your method of contraception and you have irregular periods this is most likely to be the cause. Different methods, including different types of the pill, the coil or the implant, can cause your period to come more often, less frequent or stop altogether, they can change how heavy or light they are too
  • StressBeing very stressed can result in your periods being less frequent and your cycle can become longer. When you are stressed your sympathetic nervous system is activated. When your sympathetic nervous system is in action, your parasympathetic nervous system (the so-called ‘rest and digest’ system) is diminished. This branch of the nervous system has control over functions such as digestion, your immune system and your reproductive functions, and so when it’s overridden, these different divisions can suffer and your periods can stop as a result of this
  • Your body weight – Being under or over weight can upset your hormones and cause irregular periods. Excessive exercise and being underweight can cause your periods to stop altogether. Being overweight can often result in heavier, more painful periods as fat cells store extra oestrogen
  • Age – You are often more susceptible to irregular periods at different stages of your life. In the first few years after starting your periods your period can take a while to settle down. This often means younger girls experience lighter period with longer cycles at the beginning, although this isn’t always the case. As a women reaches her mid 40’s she is getting to an age where she no longer wants any more babies and therefore periods are no longer necessary. In the lead up to the menopause a woman’s periods often become irregular (sometimes heavy to start with but then becoming lighter and less frequent). This is a perfectly normal and can last for several years
  • PCOSPolycystic ovary syndrome (PCOS) affects a woman’s ovaries. This means ovulation often doesn’t happen as it should and your periods can be affected as result. Your periods can become irregular and less frequent
  • Medication – A large number of medication can affect your periods so be sure to read the product information leaflet (PIL) or ask your doctor about any side effects of medication you are on. Some examples include: anti-depressant and anti-anxiety medication, anti-inflammatory medication, thyroid medications and different methods of hormonal contraception including the pill or the implant
  • Thyroid issues – Problems with your thyroid gland can also cause issues with your periods. Typically hyperthyroidism (an overactive thyroid) can cause your periods to become irregular or stop altogether.

Here we have outlined some of the possible reasons for irregular periods but it is advisable you visit your doctor if your periods change suddenly or you are in any doubt as to what is causing your issue.

What can I try at home for irregular periods?

If your periods are irregular there are some simple dietary and lifestyle factors to consider that could help:

  • Diet – Firstly being over or underweight can have dramatic effects on your periods so ensure you are eating a diet to meet your energy requirements. Next, what you eat is important to consider, fat in particular. Eating too little or too much fat can affect your periods. You need healthy fats in your diet to manufacture hormones, including the sex hormones, but consume too many bad fats and you can upset the balance of your hormones. Eat a healthy, balanced diet, rich in good fats and vitamins and minerals to help regulate your periods
  • Exercise – Similar to food, you need a healthy balance of exercise for a regular menstrual cycle. Too much exercise often goes hand in hand with minimal body fat which can upset your hormones. On the flipside so can sitting on the sofa not doing much as you are more likely to put on weight this way! Take part in regular, moderate exercise and your hormones are more likely to regulate
  • StressStress can cause your reproductive functions to diminish, your immune system and digestive health can also suffer as your body is in ‘emergency mode’. Address the stress and your periods are more likely to regulate
  • Be aware of medication – Discuss any medication with your doctor that might be upsetting your period. They should be able to pinpoint what might be causing your issues and if there are any alternatives available

Can any herbal remedies help?

If your irregular periods are getting you down there are some herbal remedies available which could help, particularly if you think a hormone imbalance or stress are to blame.

Agnus castus helps to gently support your progesterone levels, this is particularly useful if you suspect you have high levels of oestrogen and experience PMS-like symptoms, feeling very irritable, often have mood swings, feel angry, suffer from fluid retention, sore breasts and have painful, heavy periods.

Soy isoflavones are useful to address the other end of the spectrum – when women have very light, less frequent periods, and often feel weepy, have low self-confidence, feel very tired a lot of the time and may suffer from acne. Fermented soy isoflavones are very useful for women in the lead up to the menopause, but low levels of oestrogen can give rise to irregular periods at any age.

Please note if you are taking hormonal contraceptives such as the pill, hormone-balancing herbal remedies may not be suitable for you.

If stress is impacting on your periods try our Stress Relief Daytime drops. Take these and consider incorporating relaxation techniques to help you better manage your stress.

Can my doctor help?

If the root cause of your irregular periods isn’t clear your doctor can run any necessary tests to help determine where the issues lie. If your problem is sudden, ongoing or you have any additional symptoms, it would be advised you pay your GP a visit.

Agnus castus | Helps Relieve Pre-Menstrual Symptoms | Mood Swings, Menstrual Cramps, Bloating & Breast Tenderness


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A traditional herbal remedy used to relieve the symptoms of PMS
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Did you know?

Did you know the average age of starting your periods has changed? A 100 years ago, 16 was the average age for a girl to get her first period in the UK but now this has dropped to just 12! Incredible!

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