As a young woman, you were probably surprised by the sudden onset of what seemed like a life-ending disease. It's likely that you've never forgotten the unpredictably of your first period. The good news is that those years are well behind you. The bad news is that those days will be just as unpredictable on their way out as they were on their way in.

Menopause, that stage in a woman's life when her period ceases, can be a confusing time. Like that first period, there's no definitive age when menopause will begin. It can happen in your 40s or 50s, but the average age is 51 in the United States, according to the Mayo Clinic.

And to make matters more confusing, the symptoms indicating its onset can be vague and gradual. One day you may be convinced that menopause has started, the next day you may be equally convinced that it's not, and on the third day you may feel like you're back at square one.

Fortunately, there are some guidelines that you can use to navigate these next few years to better understand where you are in the grand scheme of menopause.

Perimenopause: Let the hot flashes begin...

Sometime usually in your 40s, according to WebMD, you may start to notice some physical symptoms that signal menopause is usually a few years away. This is called perimenopause, but sometimes it's hard to tell if you're going through it. Some women have very few symptoms; others experience many changes. Some of those symptoms might include:

  • Irregular periods
  • Hot flashes
  • Trouble sleeping
  • Mood swings
  • Vaginal dryness
  • Drop in sex drive
  • Fatigue

These symptoms are triggered by drops in levels of estrogen and progesterone, two female hormones made in the ovaries. For most women, perimenopause lasts for an average of four years, but some women only experience it for about 10 months and others go through it for as long as a decade.

Your doctor can often diagnose perimenopause based on your symptoms. To help you feel better and for your overall health, it's important that you exercise, eat well, get sufficient sleep and ask your doctor if you should take additional calcium or other supplements. Your doctor may also suggest estrogen therapy to help with symptoms or lower your risk of osteoporosis.

Menopause: You've hit the big time!

Woman at a checkup with her doctor Now is a good time to check in with your doctor to confirm your diagnosis and discuss any other issues regarding your health. (Photo: Iakov Filimonov/Shutterstock)

Menopause happens because the ovaries stop producing estrogen and progesterone. Menopause is the time frame between your last period and the 12 months after that.

Menopause is a natural part of aging. But it can also be a result of certain illnesses, treatments or surgery, reports WebMD.

Although the average age of menopause is 51, it can start earlier or later. If you start before you turn 40, that's called premature menopause. When you go through menopause typically depends on your genes.

During menopause, you might have some of the same symptoms as perimenopause, except for the irregular periods, so treatment is the same as perimenopause. Eat right, exercise and take any supplements your doctor might suggest.

Signs and symptoms are usually enough to diagnose menopause, but your doctor can also perform blood tests to check the levels of follicle stimulating hormone (FSH) and estrogen in your body. Sometimes those levels can be misleading because they fluctuate during perimenopause and aren't accurate if women are taking birth control pills.

Postmenopause: Congratulations, you made it, (or did you?)

Smiling mature woman Now that it's over, you can finally put those pesky menopause symptoms behind you, right? Unfortunately not. (Photo: ESB Professional/Shutterstock)

According to the Cleveland Clinic, a woman is considered to be postmenopausal when she hasn't had her period for an entire year (for natural reasons).

It's tempting to think that once you have reached this stage, you can put all of those symptoms and hormone fluctuations behind you. Ah, if only it were so. As estrogen levels continue to decrease, you might still experience some symptoms for several years, even after your periods are a thing of the past.

Some studies have found postmenopausal symptoms can include hot flashes, mood swings, insomnia, vaginal dryness, headache and difficulty concentrating. It's important to keep eating right, exercising and checking in with your doctor for help with your symptoms.