You’ve probably heard of menopause, commonly known as the point at which a person’s menstrual cycle stops for good. But it might surprise you that many symptoms that occur during menopause actually begin a lot earlier, during a phase called perimenopause.

Perimenopause refers to the time period when people start noticing inconsistency in their menstrual cycle, up until menopause actually begins. Menopause technically starts when someone has gone 12 months without a period. According to Nanette Santoro, chair of the Department of Obstetrics and Gynecology at the University of Colorado and a menopause researcher, “the transition is marked by either a seven day or more increase in variability in your cycle length, or a skipped menstrual period.”

This isn’t to be confused with the word premenopause, which you may have heard tossed around before. That refers to the time up until a person starts experiencing menopausal symptoms (so basically now, if you’re a person who gets a period), said Alyssa Dweck, author and New York-based gynecologist practicing for over 20 years.

Given that all the terminology, symptoms and timing can make an already confusing er, period, even more complicated, HuffPost chatted with experts on all things perimenopause to make it a little more clear. Here’s what you should know about when it can happen, what to expect and how to alleviate any annoying issues:

When does perimenopause start?

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While there’s no way to pin down the exact age someone experiences perimenopause, Santoro said the average individual begins their transition with a skipped period or a “noticeable difference in variability” of their menstrual cycle in their 40s. By the time someone is 49, they may have gone approximately 60 days without a menstrual period. By 51 or 52, they are typically menopausal.

Santoro noted that some people can start experiencing perimenopause as early as their 30s. However, this isn’t incredibly common. According to Dweck, people experiencing missed periods in their mid- or late-thirties should more likely test for pregnancy or another condition, like a thyroid abnormality, than jump straight to perimenopause as a culprit. (And even if your unpredictable periods are due to perimenopause, Dweck still advised using contraception if you’re not trying to to get pregnant.)

The length of perimenopause varies, with the average lasting a few years. For some people, it can last up to a decade.

What are the symptoms of perimenopause?

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Beyond period irregularity, a whole host of other symptoms accompany perimenopause, which are pretty similar to those most people typically associate with menopause. These can ramp up in severity the closer you get to the point where your menstrual cycle stops completely, Santoro said.

One of the most often discussed issues is hot flashes, AKA “the overwhelming and very rapid onset of heat that moves its way up to your face and head, during which you will start to perspire like crazy,” Dweck said. When they occur at night, they’re often referred to as night sweats.

There’s also mood fluctuation. During perimenopause, people will likely start to notice some irritability, anxiety and depression.

“Women are at risk to have their first lifetime episode of major depression when they’re perimenopausal,” Santoro said, which was a symptom she discovered during her research. “And about 15 to 25 percent of women will report an increase in what we call depressive symptoms.”

Finally, both experts said people can expect worsening sleep and increased vaginal dryness. Part of the sleep interruptions can be attributed to waking up during hot flashes, according to Santoro, but another culprit is hormone fluctuation (the hormone changes also cause the vaginal dryness). Until perimenopause, the hormones estrogen and progesterone cue your regular menstrual cycle. After, they become erratic and trigger the period irregularity and other symptoms, Dweck explained.

What factors affect perimenopause?

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If you’re hoping for a bit of insight into what your perimenopause experience might be like, both Dweck and Santoro suggested looking at your family history, since genetics play a role. Lifestyle is also a factor.

“If your mom had an early menopause, and your lifestyle is similar to hers, it’s very likely you will go through a very similar scenario,” Dweck said, adding that smoking is an important lifestyle factor to consider, because smokers “notoriously go through earlier menopause.”

Weight and ethnicity can also play a role. Santoro said that being overweight is associated with more severe hot flashes, and that according to her research, black individuals tend to have the longest lasting and most severe hot flashes. Asian Americans have shorter and less severe hot flashes, and white individuals fall somewhere in the middle, she said.

So, what can you do about all of this?

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If this all sounds inevitable and overwhelming, there’s hope. Perimenopause and menopause can have a big impact on your life, but there’s a lot to be gained from having open and honest conversations with your health care provider to discuss treatment options.

For starters, it may be a good time to start considering lifestyle decisions, like increasing your exercise and consulting a nutritionist, Dweck said. It goes without saying, but you’ll probably want to quit smoking for a number of reasons. You can also learn to avoid or limit triggers for hot flashes, which Dweck said include alcohol, particularly red wine, caffeine and stress.

Hormone therapy is another route, Santoro added, although there are some risks and side-effects associated with it. This is essentially putting the hormones you’ve lost — estrogen and progesterone — back into your body, which helps with just about every perimenopausal symptom.

If hormone therapy isn’t an option for you because, for instance, you’ve had certain cancers or are prone to blood clots, FDA-approved medications are available on the market to fight hot flashes. Santoro also said a lot of research on hot flash prevention is ongoing. One clinician, she said, is even working on an experimental drug that blocks the brain receptors responsible for hot flashes altogether.