What Can I Expect With My First Period?

Dr. Jolene BrightenPublished: Last Reviewed: Period Leave a Comment

Puberty can be a confusing time for young women. Bodies are changing rapidly — breasts are starting to develop, body hair is beginning to grow, the shape of your body is changing, and the anticipation of the first period is looming. 

The onset of your first period can be scary if you are not prepared for it

In this article, I'll share my tips on what you should know about your first period. 

When Will I Get My First Period?

In developed countries, the average age young women have their first period (menarche) is 12 to 13 years old. Note that this is just the average age, and many young women start their periods younger or older than this. This is usually not cause for concern. 

However, if you have not started cycling by 15 years old (or if you aren’t cycling three years after your breasts began to develop), there may be something going on, and it might be a good idea to ask your parents to talk to your doctor about it.  

On the flip side, if you start menstruating before age eight, consult your doctor as well. 

It’s also important to note that when you first start cycling, your brain and ovaries are just starting to “talk,” and miscommunication can happen. This might look like irregular periods or mood swings. It can take a couple of years for the communication between the ovaries and the brain to mature. 

What Causes Your First Period (Menarche)?

“Menarche” refers to the first period a young woman experiences. The changes in hormones that prepare the body for reproduction also result in menstruation. 

Prior to you ever getting your period, the hormone estrogen will rise to thicken the uterine lining. Following this, ovulation will occur, which is when an egg is released. If the egg is not fertilized then the result will be your period. You can learn more about the details of how the menstrual cycle works here.

When Will I Get My First Period?

While there is no hard and fast rule for determining when you will have your first period, there are often physical signs that periods are coming in the near future. 

These signs include:

  • Changes to the nipples and breasts
  • Growth of pubic hair (and other body hair)
  • Changes to body shape (e.g., the hips might begin to get rounder)
  • Vaginal discharge

For some, symptoms of PMS like bloating, breast tenderness, acne, food cravings, and mood swings will show up several days before your first period. For others, that first period seemingly comes out of nowhere with no warning. 

How Long Should My First Period Last?

A typical period will last 3-7 days. There may be several cycles where it is very light, lasting only a couple of days. If this persists, speak with your doctor.

If your period is longer than 7 days or is very heavy then this is also a reason to see a doctor.


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Can A First Period Last Two Weeks?

While periods can be unpredictable for the initial menstrual cycles, a two-week-long period is not normal and warrants a trip to the doctor. Usually, periods range in length from three days to seven days. The very first period may not be more than spotting daily. 

How Long Is A Normal Menstrual Cycle?

It can take some time for the body to settle into a pattern in terms of menstrual cycles. A cycle may be anywhere between 21 and 45 days long for the first few years. Cycle length may change month to month for a while.

Your menstrual cycle is counted from day one of your period until the next. 

For young women who are about two years past menarche, a cycle less than 21 days or more than 45 days should be discussed with your provider. The average length of the menstrual cycle is 28 days, but many women experience slightly longer or shorter cycles, which is perfectly normal and healthy.  

What's An Abnormal Menstrual Cycle Length For A Teenager?

If you’re experiencing cycles shorter than 21 days, longer than 45 days, or cycles that follow no pattern whatsoever, this may be a sign that something is going on with your hormones that needs attention.

But keep in mind that when we are first starting our periods, a lot is going on hormonally that never happened before in the body. So there is no “normal” cycle length that is set in stone for young women still going through adolescence. 

And our bodies are all different, which is why saying every woman’s cycle is 28 days long is inaccurate and misleading. 

Understanding Teenage Hormones

All parents were teenagers once, but not all parents remember what being a teen was like. For some youth, adolescence is a time of turmoil and confusion, which can feel isolating. If parents better understand their children's hormones as they enter their teen years, they can help support them. 

How Can I Balance My Teenage Hormones Naturally?

Erratic periods and PMS symptoms may indicate hormone imbalance in adults, but that may not be the case for adolescents. Unpredictable cycles are completely normal for the first several months of menstruation, while your brain and ovaries establish a line of communication. Your body usually needs to go through several months of cycles before things settle into a regular rhythm and even then, it may take some a bit longer. 

Parents: if your teen has been having periods for a year or two and her cycles haven’t stabilized, it may be time to look into an underlying condition like PCOS or hypothyroidism

She can safely try some of the same methods for optimizing hormones as adults do, like seed cycling, a nutrient-dense diet, and sleep hygiene. Poor sleep is incredibly problematic for anyone’s hormones and during our early menstrual years it is no exception.. 

Can A Teenager Have A Hormone Imbalance?

Unfortunately, yes, teenagers can have a hormonal imbalance. And because hormones are already in flux during the teenage years, deciding what’s normal and what’s a hormonal imbalance can be much more difficult. 

However, there are a few signs of a potential hormonal imbalance, such as:

  • Periods that last longer than a week
  • Cycles longer than 45 days or shorter than 21 days (however, irregular periods are expected during the first few years once a young woman starts her cycle)
  • Bleeding that is so heavy, it requires a pad or tampon change every couple of hours
  • Severe cramping 
  • Unexplained weight gain
  • Hair growth on the chin or abdomen
  • Hair loss (on the head)
  • Extreme fatigue
  • Acne
  • Extreme mood swings

These symptoms can be signs of estrogen excess, endometriosis, thyroid dysfunction, cortisol imbalance, and PCOS (Polycystic Ovarian Syndrome). 

How Do Hormones Affect Teenage Behavior?

Puberty brings about a surge of hormones, and these hormones can affect a person’s behavior as they transition from childhood to adolescence. In girls, this hormone surge begins between the ages of nine and ten years old. 

During adolescence, increased testosterone levels have been associated with increased reactivity to reward. Interestingly, research has shown that testosterone levels are lower in girls who are bullied than in their peers who are not bullying victims. This indicates that one’s social environment also plays a role in hormones and by extension, behavior. 

Researchers have also found a link between increased estrogen levels and higher risk-taking behavior in teenage girls. 

Hormones can impact everyone’s behavior — no, it’s not just teenagers. But knowing their hormones can affect you can help you have a little more understanding and also tune into getting support when needed.

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  1. ACOG. Your Changing Body: Puberty in Girls. The American College of Obstetricians and Gynecologists.
  2. Coyle Institute. Understanding Teenage Hormone Imbalance. Coyle Institute.
  3. Peper JS, Dahl RE. Surging Hormones: Brain-Behavior Interactions During Puberty. Curr Dir Psychol Sc. 2013. 22. 134-139.
About The Author

Dr. Jolene Brighten

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Dr. Jolene Brighten, NMD, is a women’s hormone expert and prominent leader in women’s medicine. As a licensed naturopathic physician who is board certified in naturopathic endocrinology, she takes an integrative approach in her clinical practice. A fierce patient advocate and completely dedicated to uncovering the root cause of hormonal imbalances, Dr. Brighten empowers women worldwide to take control of their health and their hormones. She is the best selling author of Beyond the Pill and Healing Your Body Naturally After Childbirth. Dr. Brighten is an international speaker, clinical educator, medical advisor within the tech community, and considered a leading authority on women’s health. She is a member of the MindBodyGreen Collective and a faculty member for the American Academy of Anti Aging Medicine. Her work has been featured in the New York Post, Forbes, Cosmopolitan, Huffington Post, Bustle, The Guardian, Sports Illustrated, Elle, and ABC News. Read more about me here.