Drew Barrymore, 48, opens up about going through perimenopause. Here's what an expert wants you to know.

Menopause is defined as the time 12 months after a menstruating person has gotten their last period. However, what many people may not realize is that there's a phase between a woman's regular menstruating years and menopause, known as perimenopause.

In an interview on CBS Mornings, Drew Barrymore and Gayle King sat down with CBS News correspondent Nikki Battiste in which they detailed their own experiences with this phase of life.

“I realized that I was in perimenopause when I started having my period every two weeks,” Barrymore explained, saying that her heavy flow was like that of “a teenager.”

Her doctor told her that having a heavy period could last 10 years.

King echoed that experience, explaining, "I'd never even heard the phrase perimenopause until I went to the doctor because you know, not to get too graphic, but when it first happens for a lot of people it looked like a crime scene.”

She acknowledged that not everyone had her symptoms, which included hot flashes. “I know some women who have been through it and they've just sort of sailed through to have had very minimal things,” King said. “It wasn't disruptive to their life. That was not my experience.”

Women's health expert Dr. Jennifer Wider tells Yahoo Life that perimenopause typically starts in a woman's 40s.

“The symptoms can vary from person to person but often include: changes in menstrual cycle, hot flashes, night sweats, vaginal dryness, mood swings, weight gain, disrupted sleep, foggy brain and changes in libido,” she says.

Typically, perimenopause lasts for around four years, before transitioning into menopause, which is considered the official end of a woman's menstrual cycle.

“It can start earlier and last longer or for less time,” Wider explains. “There's no official badge! But if you experience one or more of these symptoms on the regular, it's likely perimenopause.”

While it's still possible to get pregnant when in perimenopause, your odds go down significantly. However, “once menopause occurs, you can no longer get pregnant,” says Wider.

Both Barrymore and King chose not to have hormonal treatments during perimenopause. For Barrymore, she felt she was not far along enough in perimenopause to require treatment. While hormones are still prescribed by health care providers to help with symptoms, Wider says that these treatments are not quite as common as they once were.

“The treatment was typically systemic hormones to counteract the fluctuating hormones causing the symptoms,” Wider explains. “Doctors don't prescribe this as readily anymore because there is some risk involved, depending on a woman's personal and family history of disease. Other treatments include topical estrogen cream, antidepressants and gabapentin, specifically for hot flashes and/or headaches.”

One thing that Barrymore also wanted to share about her perimenopause journey? It’s not the end of the road.

“Women in their 40s, 50s and 60s are looking so attractive and feeling so vibrant, living their best lives,” she said. “The way menopause has been branded is, ‘You’re old, you're done.’ That's not it.”

Wellness, parenting, body image and more: Get to know the who behind the hoo with Yahoo Life's newsletter. Sign up here.