The monthly cycle

The monthly cycle
Soon having periods will seem as natural to you as breathing. Learn here about the monthly cycle that causes them and what is happening in between.

What is the menstrual cycle?

The time from the start of one period until the next is around a month, which is why it is called your “menstrual cycle”. (The word comes from the Latin for “month”, which is mensis.) To make it easy to measure, and to discuss with a doctor or gynaecologist, we call the first day of your period “day one”. Menstruation is often the only thing you’ll notice about the changes that go on inside your body each month, but a lot is going on behind the scenes!

The animation shows you exactly what is happening during the menstrual cycle. You can just play it through or click directly on the subject that interests you.


How many days should there be between periods? 

One egg matures in one of the ovaries approximately every four weeks.
This is only an approximate figure – the menstrual cycle is very unique to every girl! It’s sometimes longer or sometimes shorter. Look at the two examples below to see how different menstrual cycles can run: The first cycle lasts 28 days, which corresponds to the average. With 33 days, the other cycle is clearly longer – but still totally normal. Please be aware that the information on fertile days and ovulation times in both menstrual cycle illustrations are only approximate guide values. If you would like to know what happens on the individual days, just start the animation.


What if my periods are irregular?

When you first begin having your periods, they are often irregular. So don’t panic if your period sometimes doesn’t start on the calculated day. It sometimes takes several years for your hormones to come into balance and your periods to become regular. Diet, stress, travelling and other factors can also cause variations in your cycle. 

If you have any concerns, or want more information speak with your doctor.

Quick menstruation facts: What, how long, how much and how heavy?

What? The fluid that comes out of your vagina during menstruation consists of far more than people think and not just blood. It also contains vaginal discharge and shed uterus lining. The colour of the menstrual fluid can vary greatly in appearance from red to brown to dark brown.

How long? Periods generally last between three and seven days. Again, this can vary in all girls and women – there is no “normal” in the world of periods!

How much? As with other features of the menstrual period, the amount of blood and tissue that are discharged varies quite a lot between women.  Around 65 ml of menstrual fluid is about average – that’s about half a cup full in total. Doesn't seem so much when you view it like that, does it? 

Which are the heaviest days in the menstrual cycle?

You will see that there can be heavier and lighter menstruation days. At the beginning of your period, the flow is usually heavier, with around two thirds of the menstrual fluid discharged in the first 2 or 3 days. At the end of your period there will be the “lighter days”, when the remaining third is discharged. This too can also vary from girl to girl, though. You will get used to your own cycle and will pretty quickly learn when to use different sizes of tampon.


Will my periods be the same throughout my life?

Your period will not always remain the same and may change when you are older. Most women experience changes in the duration, heaviness and progression of their periods over the course of their lives. Periods are less regular when they are first starting, and also as women approach the menopause.  Taking the contraceptive pill may cause them to be lighter than they were before and will usually cause them to be more regular. Many young mothers find that their periods are heavier after the baby is born. For this reason there are tampons in different sizes and levels of absorbency and even with extra protection wings – so you’ll always be able to find one that’s right for you. You can learn about which tampons are suitable for girls who are just starting their periods here.