Menarche: First menstruation – what happens in the body?
The very first menstruation has a name: menarch. Just like the very last one, menopause is called.
And whether it comes quietly and almost unnoticed or as a surprise in the middle of an ordinary school day, it is a major milestone. Both for you and for the adults around you.
Your first period is your body's way of saying:
👉 Hey! You are in the process of becoming an adult.
In some cultures, it is celebrated big with a party, a dinner, with very special rituals, also with other women. In other cultures, it goes almost unnoticed. And unfortunately, there are also some cultures where having a period is still met with stigma and shame.
Before I go any further, I want to quickly say this to you: Menstruation is a completely natural biological process and function in the body, just like we sneeze, cough, pee, blink our eyes, that we move - completely without thinking about it. The body just does. Because it has to - it can for a reason. And so it is with menstruation. It's just as natural as any other process in the body, and you have no control over it. Therefore, you should not be ashamed, hide it away or be embarrassed.
The menarch, your very first period, marks the start of a new phase in your body – both physically, hormonally and emotionally.
👉 See our selection of menstrual panties and menstrual swimwear for teens here.
And if you ask us: It deserves to be met with curiosity, knowledge and security.
Article written by Cathrine Widunok Wichmand
When do you get your first period?
If you want to know the date, I understand you. But the body is not yet that predictable. But in fact, there will be a number of signs that your period is on its way - before it actually starts.
When we talk about age, there are small fluctuations in terms of. how old you are at the time of the first bleeding. In Denmark, and in general the Western world, many people get their first period around the age of 12 , but anything between 9 and 16 years is completely normal.
It's quite a wide range, as you can sense - I was ten years old myself. And it can be difficult to be the first in the class - just as it is not nice to be the last. It's completely normal that we want someone to lean on, and we want to be a bit like the others.
But.
There is no one right time.
Your body follows its own pace.
What happens in the body before the first period?
The Menarch does not come out of the blue. The body has been working for a long time.
Your period is generally about maturing eggs - which are released, and as long as you are not pregnant, they come out together with the uterine lining and blood during menstruation.
You were born with your eggs - they were formed while you were inside the womb.
Now we dive into what actually happens before the first period:
1. The brain sets it all in motion
It all starts in the brain.
The pituitary gland (a small gland in the brain) starts sending signals in the form of hormones to your ovaries, where your eggs live.
The hormones are called, among other things:
- FSH (follicle-stimulating hormone)
- LH (luteinizing hormone)
They tell the ovaries that it's time to start maturing eggs.
2. Estrogen changes the body
When the ovaries are activated, they begin to produce estrogen.
Estrogen is one of the most important hormones during puberty, and it affects the body in many ways:
- The breasts start to develop (they may feel sore, as if there is a small hard ball inside them suddenly)
- The hips change shape (they slowly become a little wider)
- Hair appears under the arms and around the genital area
- The uterus begins to grow (therefore you can also get a nice smaller elevation on the stomach below the navel - just like you may have seen on ancient statues with women's bodies)
It can feel unfamiliar – maybe even a little overwhelming. A lot will be different - but fortunately it will not happen all at once. And all changes also happen because they have a function. Your body has new features.
The body is in the process of building something up.
Something that can create life in adult life.
One day you may have to be pregnant so that the uterus grows. In that case, you should also be able to carry the baby so that the pelvis expands and the hips become wider. Maybe you need to breastfeed - so that the breasts get bigger and ready to be able to produce milk one day.
It's actually pretty crazy. Your body is amazing.
3. The uterus begins to work
At the same time as the hormonal changes, the uterus begins to prepare. In principle, it prepares to be able to have a child every month - it's definitely not exactly on your radar now. But it is the focal point of your period.
Every month, the body builds up a completely new mucous membrane inside the uterus, where a fertilized egg can attach.
It is soft and filled with blood vessels – ready for a possible pregnancy.
If fertilization does not occur, the body lets go of both the egg and the mucous membrane.
👉 The mucous membrane and egg are secreted – and it comes out of the vagina as what you call menstruation.
4. The first cycles are often irregular
Once menstruation starts, the cycle is rarely regular. This is because the body is still finding its rhythm.
- There can be a long time between bleeding
- It may come unexpectedly
- It can be very light or a little stronger
It's completely normal. For many, it takes 1–2 yearsfor the cycle to become more stable.
Tip: Mark your calendar on the day your period starts - over time it will help you to find out approximately when your next period starts.
You will also experience the irregularity later in life - when you get into perimenopause, the period leading up to the very last period, the menopause, which I mentioned very first.
The irregularities in your cycle, both near the menarch and menopause, are about your hormones, which fluctuate up and down. At the menarch when they are settling in. At menopause, the amount of estrogen begins to divide.
5. Ovulation – but not always in the beginning
In a more 'mature' or regular cycle, ovulation occurs about two weeks before menstruation. The actual time of your ovulation is unique to you - the way you can find out the time it is by tracking your temperature (it rises slightly around ovulation), your discharge and your cervix. 👉
Read more about how you can use your discharge to track your cycle here.
But in the beginning, you will often have many periods without ovulating. It's part of the body's run-in – and not something you need to worry about.
6. Physical and emotional changes
The Menarch is not just something that happens in the body – it can also be felt inside. In your thoughts, feelings, and in your mood. Maybe you've had several disagreements with your parents or friends lately?
This is completely normal, and many people experience:
- Mood swings
- Increased sensitivity
- Fatigue
- A feeling of not being able to fully recognize yourself
It is the hormones that work. Your hormones affect everything in the body, especially your sleep, your energy and your mood.
And you don't want to be the first to look in the mirror one morning and think, "WHO AM I?!" because everything is followed differently. You will probably experience this continuously, cycle by cycle.
You remember the hormone estrogen, right? This is also called the Beyoncé hormone. It can make you feel on top of your game and like someone who wants a thousand appointments. But as soon as you have ovulated, estrogen levels drop and progesterone rises. It's like changing gears in the car - it can be felt for many in mood and energy and surplus. This is what is called PMS. Premenstrual symptoms, and up to 80% suffer from them.
👉 Read more about what PMS is in the article here.
When PMS is severe, and it is for about 8% of us, then it is called PMDD. Premenstrual dysphoria, and here it is not just a matter of having a slightly boring day, but pervasive, depressive thoughts and pronounced exhaustion.
You should not have to deal with this alone, in which case you should talk to a caregiver and your doctor.
The risk of PMDD is significantly increased if you are neurodivergent with ADHD. Your risk of PMDD increases to about 24%, and if you are taking medication, its effect can fluctuate by 600% during your cycle. It's worth keeping in mind and talking to your psychiatrist about it.
👉 In this article, you can learn more about PMDD and understand the symptoms.
You're not behind – and you're not too early
One of the biggest concerns is often:
- "I'm the first"
or
- "I'm the last"
You don't really want to be one or the other. But the truth is:
There is no right time.
Bodies develop differently.
And it says nothing about you – or your body.
You are not wrong, and your body does exactly what it is supposed to do, when it has to. If you are unsure, talk to a caregiver, a friend, a teacher or the health visitor at your school.
How to make it safer
The great thing about menstruation is that it's not something you have to learn. Your body does what it does. But it is important that you feel safe.
It may help you to:
- Talk to an adult you trust
- Ask when something feels unclear
- Write down thoughts or questions
- Get to know your body at your own pace
And perhaps most importantly: Give yourself permission to be curious rather than not perfect. If you talk about your thoughts out loud with girlfriends, you will be confident that you are guaranteed to have thought several of the same thoughts.
When your period comes for the first time
Den første menstruation er ofte:
- Years
- Short
- Unpredictable
It's completely normal. Maybe it's not at all what you thought it would be.
Then there's the blood itself. The bleeding may be:
- brownish
- Pink
- red
But what can you do to be prepared for the sudden? Keep track of the internship. And that is what happens now.
What do you do in practice?
This is the key to a good experience. To be a little practically prepared. It can mean several things, e.g. having read a book or two about the body. I highly recommend you The Girl Book or It's Just Blood, both of which explain to you what happens in the body.
Then there are the products themselves. What do you need for your period? You need something to absorb the blood, at least that's what most of us think is nice. Here you will probably have to try your hand at it. What feels good to you?
Many start with:
- Menstrual panties
- Bind
- Extra underwear in the bag
For many, menstrual panties are the easiest solution in the beginning because:
- they do not require you to learn something new
- They feel like regular underwear
- They look like regular underwear - no one can see that you have your period
- Period panties are also smart when you have irregular bleeding at first - it's one of the few products you can use without bleeding - but still feels nice.
👉 See period panties for teens from Flow here.
A new phase – nothing dangerous
Your body is a bit being 'upgraded'. A lot of buttons are being pushed. At the same time. Maybe it all feels a bit big? Maybe a little confusing?
But what you're in the middle of is something millions have experienced before you. Billions actually. Also those around you.
Your mother. Your aunt. Aunt. Your friend. Your teacher. And slowly as you land in the new, everything will also feel a little more recognizable and a little more like you. Now your body can do a lot of new things - it's actually pretty cool.
As a little tip, I would recommend you to find good books or movies that are about menstruation or the hormone change that happens in the body. It could be the Disney movies Red or Inside 2. It could also be, for example, the Mira books or the Me - a girl book. 👉
See our small curated selection of good books here.
The final word
Remember that all the new things, your period and cycle, are not something you have to 'master' or manage in a 'right' way. You will slowly get to know your body and get to know it.
As an adult who has been menstruating for almost 27 years, I am still learning new things about my body and my cycle. It changes periodically throughout your life, and the best thing you can do is to be curious - and if something in your body doesn't feel right, then you should say it out loud.
Loveliest hugs, Cathrine - founder of Flow and mother of 2.
Do you have questions about the first period? Here we have gathered the most common questions and answers so that you can feel safe and well prepared.
FAQ: The first menstruation (menarch)
When do you get your first period?
Most people get their first period between the ages of 10 and 15, with an average around 12 years. It is completely normal to be both earlier and later – the body follows its own pace.
What are the signs that your period is coming?
The most common signs are:
- Discharge (white or transparent)
- Breast development
- Hair under the arms and around the genital area
- Mood swings
- Slight murmuring in the abdomen
Menstruation often starts 6–12 months after you start to have discharge.
What does the first period feel like?
The first menstruation is typically:
- Years
- Short-lived
- Irregular
The bleeding can be brownish, pink or red, and it can come on a little unexpectedly.
Is it normal for menstruation to be irregular at first?
Yes. It is quite normal for menstruation to be irregular for the first 1–2 years.
The body is still finding its rhythm, and there can be both short and long periods of time between bleeding.
Do you ovulate from the start?
Not necessarily. In the beginning, many people have periods without ovulation. It is a natural part of the body's development and becomes more regular over time.
Which products are best for the first period?
Most people start with:
- Bind
- Menstrual panties
For many, menstrual panties are the easiest solution because they:
- does not require introduction to the body
- Feels like regular underwear
- Provides security throughout the day
👉 See period panties for teens from Flow here
Can you go to school and play sports with menstruation?
Yes, definitely. You can do everything the same as usual – go to school, play sports and hang out with friends. If you want - you can feel your energy and surplus yourself. With the right products, menstruation feels like a normal part of everyday life for many.
Does menstruation hurt?
Some experience slight pain or murmuring in the stomach, while others hardly feel anything. Both are normal. If the pain is very severe, you should tell an adult so that you can talk to the doctor about it.
👉 In this article, we have collected 5 good ways to reduce menstrual pain.
What do you do if your period starts at school?
It happens to many people – and that's okay. You can:
- Using toilet paper temporarily
- Ask a teacher or friend for help
- Have extra underwear or period panties in your bag in the future
The most important thing is: you're not the only one it's happening to.
Should you talk to someone about it?
Yes – it can make a big difference. It can be:
- a parent
- In Venom.
- a teacher
- Another adult you trust
You don't have to figure it all out yourself.
