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Science Lab

What causes irregular periods?

Menstruation/periods are called irregular when the length of the cycle is more than 35 days, or if the duration varies every time it happens. There are multiple causes for an irregular cycle. for the same. Let’s dig into the reasons in this week’s Science Lab.

Irregular Periods in Teenagers

Photo: Shutterstock/Sino Studio/Person in the photo is a model. 

The average length of a woman’s menstrual cycle is 28 -32 days, but this varies from person to person. However, many times, the length varies every cycle and is irregular. For example: If your last cycle was 28 days long but the next cycle is 30 days long, and the next one 29 days; this is not very irregular.

But if your last cycle was 30 days long and you missed the periods the next month and then your new cycle is 25 days or 35 days; and this continues for many cycles – you have irregular periods. Let’s find out the top reasons behind irregular periods: 

You have just started your periods

For most girls, periods usually start during puberty, between the ages of 10 and 16 years. In the initial few months, the periods are not very regular as your body is still getting used to it. So, don’t panic. Track your cycle every time it happens. It takes around two years for the periods to become regular after they start. 


Medicines, the one you took for your cold or some other ailment, or thyroid disorder or acne etc can also lead to irregular cycles. These could be the side effects. 

Weight fluctuations

Menstrual problems can also be caused by rapid weight gain or loss. So if you have been ‘dieting’ or just surviving on soups or salads for getting that figure, stop right there! Improper eating will ruin your metabolism and wreck your menstrual cycle.

On the contrary, if you have been a couch potato and just eating chips, chocolates and all the junk foods while not getting up from your bed; that too will result in sudden weight gain/obesity and wreak havoc with your health and menstrual cycle. So get up, help in household work, exercise and eat right! See a nutrition expert if you need help with your body weight.

Obesity in young women can also contribute to high levels of androgen-called male hormones. Androgen deficiency, which results in infertility, can cause irregular menstrual cycles and block ovulation.

Poor nutrition

Poor diet, which lacks essential vitamins and nutrients, causes hormonal disbalance which makes the period cycle irregular. Excessive intake of unhealthy foods, like refined foods (white bread, refined flour (maids products), biscuits/cookies/cakes, takeaways etc) and outside food can also lead to irregular periods. So try and eat home-cooked meals at least 6 days a week if you want regular cycles. 

Over exercising

Being a fitness freak is good but intense training and not listening to your body is not. This also leads to sudden weight loss and hormonal imbalances and can be one of the reasons for irregular periods. Also, if you recently started working out, it too will affect your menstrual cycle by increasing metabolism.

Medical conditions

Medical conditions like Polycystic ovarian disease (PCOD), Thyroid disorders, Endometriosis etc also lead to irregular or sometimes painful periods. These conditions get diagnosed by the doctor only on analysing your symptoms. Visit a doctor if your periods have been irregular and extremely painful. 


Everyday stress creates changes in menstruation. High stress, studying till late at night and not getting enough sleep, being awake all night and sleeping till late afternoon messes up with your body’s functions and causes irregular cycles. Also, if you are really excited about something like an upcoming movie/song of your favourite artist or feeling nervous about your stage performance; this too can make your cycle irregular. 

Eating disorders

Eating disorders, such as anorexia (not eating/avoiding food) or bulimia (eating a lot of food and then throwing up) are caused due to stress or other psychological issues. These disorders can also lead to irregular menstrual cycles. 

reasons for irregular periods

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This article was first published on May 28, 2023. 

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