Causes of irregular periods in 20s

Gytree Team
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Premature Menarche: The EarlyKnock of Periods in Women

Verified by Dr. Vaishali Sakpal Rane (MBBS, DGO Obstetrics and Gynaecology, DNB Obstetrics and Gynaecology)

Your menstrual cycle can vary slightly in length from month to month, during certain phases of your life like puberty, breastfeeding, or approaching menopause. Irregular periods may not always indicate a problem, but there can be various causes of irregular periods in your 20s which you should not ignore. It's always a good idea to see a doctor to be assured.

What are irregular periods?

If the length of your cycle keeps changing drastically, you may have irregular periods. Menstrual cycles shorter than 21 days, and longer than 38 days long, or cycle length varying significantly, can indicate irregular periods. The average menstrual cycle length is 28 days, but it's okay if your menstrual cycle varies a little.


Usually, many women develop a regular menstrual cycle after 1 or 2 years of starting their periods, but it's common for it to vary by a few days each month.

Causes of irregular periods in 20s

Here are some causes of irregular periods in 20s:

  • Early pregnancy – pregnancy is one of the most common cause of missed periods, if you are sexually active take a pregnancy test to rule out this cause
  • Some types of hormonal contraception – if you are using hormonal contraceptives like the pill, patch, implant, hormonal IUD, you may experience irregular bleeding during the first few months. Some people can have no period at all, while others may experience withdrawal bleeds. Similarly, if you stop using hormonal birth control, you can have irregular periods. This happens because your body takes time to begin working normal again.
  • Polycystic ovary syndrome (PCOS): PCOS is also a very common cause of irregular periods in 20s. In polycystic ovary syndrome, there are small fluid-filled sacs that may form in the ovaries which can often be seen on an ultrasound. The hormonal imbalances can prevent eggs inside the ovaries from maturing, and thus causing anovulation and irregular periods. Sometimes a woman with polycystic ovary syndrome can stop menstrual cycle completely for many months.
  • Eating disorders like anorexia nervosa, bulimia nervosa, and binge eating disorder, can often mess up with the menstrual cycle causing absent or irregular periods. 

Irregular periods aren’t always a sign of something serious but you must visit a gynaecologist to find the root cause and be assured.

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