How do periods change over time?

What age do most people start their periods?

Most women start their periods between the ages of 10 and 15. The average age is 12 to 13. Throughout your lifetime you will have around 350 to 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 them 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.

You might experience a delay in starting your periods if you’re:

• underweight
• have chronic illnesses
• are very stressed

When you start your periods can depend on your ethnicity too. Studies show that on average, black girls are likely to start their periods earlier than white girls. If you have not started your periods by the age of 15, or within three years of your breasts starting to develop, then it’s a good idea to see a doctor.

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 hormonal treatments or medicines affecting hormone levels.

Gynaecological conditions can affect your periods. These include:

• endometriosis
• polyendocrine metabolic ovarian syndrome (previously polycystic ovary syndrome)
• pelvic inflammatory disease
• cancers of the reproductive system

When do periods go back to normal after pregnancy?

You might start having periods as soon as four to six weeks after giving birth if you don’t breastfeed. Because ovulation can occur before your first period, contraception is recommended from around three weeks 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 cause 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.

When do most people enter the menopause?

In the UK the average age of 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 to 45 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.

It’s normal for your periods to vary greatly over a lifetime. If you have any concerns, reach out for support from a GP.