If you're in your late 30s to early 40s, you wake up in a sweat at night, your periods are irregular and are often accompanied by heavy bleeding (or hardly any bleeding at all) — then chances are, you're going through perimenopause.

While your symptoms may seem sporadic and beyond your control, it’s important not to panic or to feel overwhelmed by this often disorienting new phase. Instead, the best way to tackle your perimenopause is by understanding more about the change that is happening in your body, and why it happens. Once you understand the basics, you’ll be better equipped to embrace this transitional stage, head-on.

What is the perimenopause?

The perimenopause is the transitional phase before menopause — that is, the natural end of menstruation and your ability to reproduce. Peri is Greek for "around" or "near", and it is during this lead-up stage that women begin to experience symptoms of the oncoming menopause, from insomnia and night sweats to vaginal dryness. Although it may vary, the perimenopause lasts for about 8-10 years, with most women entering into it around the age of 39-49.

Can you predict the age you’ll reach the menopause? Find out in our article.

Is “perimenopause” the same as “premenopause”?

Although you might hear these words being used interchangeably, they actually mean two completely different things. The North American Menopause Society (NAMS) defines the perimenopause as “perimenopause is the transition phase into menopause that typically lasts for about six years”, whereas premenopause is “the time between a woman's first period and the onset of perimenopause” — essentially, her fertile years.2

What causes the perimenopause?

But, what’s happening inside the body to cause this change? Well, it’s all down to the level of estrogen in your body which begins to rise and fall inconsistently during the perimenopause. As such, many women will begin to notice that their menstrual cycles become irregular in length and flow — with heavy bleeding, or hardly any bleeding at all.1 Let’s take a look at the role of estrogen during the perimenopause in a little more detail below.

Perimenopause and estrogen 

Many of the changes you’ll experience during the perimenopause are down to estrogen — or a lack thereof.3

The amount of estrogen in our body rises and falls within a certain level throughout the menstrual cycle during our peak reproductive years. Since estrogen levels are largely controlled by two hormones, follicle-stimulating hormone (FSH) and luteinizing (LH). FSH stimulates the follicles — the fluid-filled sacs in the ovaries that contain the eggs — to produce estrogen.  Once the level of estrogen reaches a certain threshold, the pituitary gland is signaled by the brain to turn off the FSH and produce a surge of LH. It is this flood of LH that encourages the ovary to release the egg from its follicle (ovulation). After ovulation the leftover follicle releases progesterone and estrogen in preparation for pregnancy, which in turn causes the levels of FSH and LH to drop. In the case of a ovulation that does not result in pregnancy, progesterone falls, menstruation takes place and the cycle begins again.

As your ovaries age however, they release fewer and fewer hormones, meaning that there is less FSH and LH to regulate estrogen production. This leads a woman’s estrogen levels fluctuate during the perimenopause, eventually dropping off altogether once the menopause begins.

Symptoms of the perimenopause

Now that you know what is happening to your body hormonally, we discuss the symptoms that might occur as a result of fluctuating estrogen levels. Some of the keys identifiers are:4 

  • Irregular, heavier or longer periods
  • Hot flashes 
  • Insomnia 
  • Night sweats 
  • Palpitations
  • Headaches 
  • Vaginal dryness 
  • Breast tenderness 
  • Acne flare-ups

Perimenopause vs menopause: what’s the difference? 

While both stages impact a woman’s reproductive system, and have many of the same symptoms, there are some differences between the two stages. For example, many will experience their periods for the first part of the perimenopause, which means they may still be able to get pregnant. While at the menopause stage, your ovaries stop releasing eggs and producing most of their estrogen needed for reproduction. Ultimately, it's helpful to think of the perimenopause as the build-up to the main event of menopause.

How do I know I am perimenopausal? 

If you are experiencing any of the symptoms listed above, it might be worth making an appointment with your GP to make the diagnosis of the perimenopause. Before you do, it’s well worth reading our guide to perimenopause symptoms for a more in-depth review.  

To discover more great advice on how you can stay feeling your best during the menopausal and perimenopausal stages, simply visit our Menopause Guide.


  1. Mayo Clinic. (2020). Perimenopause - Symptoms and causes. [online] Available at: [Accessed 13 Jan. 2020].

  1. (2020). Menopause Glossary, Menopause Resources: The North American Menopause Society, NAMS. [online] Available at: [Accessed 13 Jan. 2020].

  1. Publishing, H. (2020). Perimenopause: Rocky road to menopause - Harvard Health. [online] Harvard Health. Available at: [Accessed 13 Jan. 2020].

  1. (2020). How Will I Know I'm in Menopause? Menopause Stages, Symptoms, & Signs: The North American Menopause Society, NAMS. [online] Available at: [Accessed 13 Jan. 2020].

  1. Cleveland Clinic. (2020). Menopause, Perimenopause and Postmenopause: Cleveland Clinic. [online] Available at: [Accessed 13 Jan. 2020].
For more support and advice, head back to our dedicated menopause guide