How do periods change over time?

Samantha Wild
Clinical Lead for Women's Health and Bupa GP
26 May 2023
Next review due May 2026

Periods don’t stay the same throughout your life. You may experience a range of changes depending on your age, your health and other lifestyle factors. Sometimes it can be hard to know if what you’re going through is normal or not. Here I’ll explore what you can expect from puberty to perimenopause and beyond.

What age do most people start their periods?

Most people start their periods between the ages of 10 and 15. The average age is 12. Throughout your lifetime you will have around 450 periods in total. But this depends on:

  • how early you start menstruation
  • how many (if any) pregnancies you have
  • when you enter the menopause 
  • how long your cycle usually is

Why do some people start their period later than others?

Your body will start having periods when it’s ready to. This is usually a couple of years after you have started puberty, but this is influenced by both genetic and environmental factors. If you’re underweight, have chronic illnesses, or are very stressed you might experience a delay in starting your periods.

When you start your periods can depend on your ethnicity too. Some studies show that black girls are likely to start their periods earlier than white girls. If you have not started your periods by the age of 16 then it’s a good idea to see a doctor for a check-up.

What can disrupt your periods?

Many different things can cause changes to your periods. These can include lifestyle factors such as gaining or losing lots of weight, and extreme exercise regimes such as long distance running or gymnastics.

Your periods can also change because of certain health conditions. These can include thyroid conditions and bleeding disorders. You might also experience period disruptions if you take medications such as steroids too. Birth control pills can also lead to period disruptions, even after you’ve finished taking them.

There are also several gynaecological conditions which can affect your periods. These include endometriosis, polycystic ovary syndrome  and pelvic inflammatory disease, as well as certain cancers.

When do periods go back to normal after pregnancy?

You might start having periods as soon as four weeks after giving birth. This is why birth control is recommended at three weeks post birth due to the chance of ovulation (which could lead to pregnancy if you have unprotected sex at this time).

Whether or not you breastfeed fully can also affect how soon your menstrual cycle begins again, and some people will be offered birth control beginning straight after birth.

How do periods change during the perimenopause?

The perimenopause is a time of hormonal changes. Your hormone levels will rise and fall before the ultimate decline of oestrogen at the end of the menopause. It’s the hormonal changes that causes a range of physical and mental symptoms during the perimenopause.

Such changes can lead you to have longer or shorter menstrual cycles. They may also affect how heavy your periods are too. If you notice bleeding between your periods, very heavy, painful periods, or bleeding after sex, see a doctor to check everything is normal.

When do most people enter the menopause?

In the UK, the average age of reaching the menopause is 51. But this can vary and is usually somewhere between the ages of 45 to 55. If you enter menopause before the age of 40 it’s considered a premature or early menopause.

You are said to have reached the menopause when you’ve not had a period for at least 12 months. But the symptoms of perimenopause can last for up to 10 years. For many people though they tend to last between 12 months and four years.

If you have heavy, painful, or irregular periods, you’ll know just how disruptive they can be, both physically and mentally. With our Period Plan, you don’t have to face these problems alone.

Samantha Wild
Dr Samantha Wild
Clinical Lead for Women's Health and Bupa GP



Julia Ebbens, Health Content Editor at Bupa UK

    • Reagan P, Salsberry P, Fang M et al. African-American/White Differences in the Age of Menarche: Accounting for the Difference. Soc Sci Med. 2012; 75(7): 1263–1270. doi: 10.1016/j.socscimed.2012.05.018

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