It’s no secret that women experiencing perimenopause, the transitional phase before menopause, often report higher levels of fatigue and exhaustion.

Multiple factors, including increased stress and hot flashes, can make perimenopausal women feel zapped. But how much you bleed during your periods could also cause or exacerbate fatigue, according to new research. 

The new study, published in the medical journal Menopause, specifically found that women who have heavier or longer periods leading up to menopause are even more likely to feel exhausted.

The researchers hope the findings shed light on the impact menstrual bleeding can have on a person’s energy levels during the transition to menopause.

“This study is a wake-up call to pay attention to all of the multiple medical problems that can lead to fatigue in the perimenopause,” Hugh Taylor, MD, the chair of obstetrics, gynecology, and reproductive sciences at Yale School of Medicine, told Health.

Although scientific research on menopause is increasing, few studies have looked at the role menstrual bleeding plays on menopausal symptoms, Siobán D. Harlow, PhD, a study author and professor of obstetrics and gynecology at the University of Michigan, told Health. 

At the same time, Harlow said, the causes of fatigue experienced by women during the menopause transition have not been fully investigated.

So, to understand if and how menstrual bleeding affects the odds of experiencing fatigue in perimenopause, Harlow and her colleagues evaluated the health data of 2,329 people between the ages of 42 and 52. The team looked at various health outcomes—including fatigue levels and how much each person bled during their menstrual period—that were recorded during seven annual medical appointments.

Reporting at least three episodes of heavy menstrual bleeding within the past six months was linked to a 44% to 62% increased chance of “feeling tired” or “worn out.” Furthermore, having three or more episodes of prolonged menstrual bleeding in a six-month window was connected to a 32% lower probability of feeling “full of pep.”

The findings persisted after the team adjusted for many factors—race, ethnicity, age, body mass index, hormone use therapy, mood disorders, perceived stress, sleep problems, cigarette use, and discrimination—that could potentially contribute to bleeding or fatigue.

According to the researchers, the study demonstrates that abnormal uterine bleeding during the menopause transition and fatigue go hand in hand. “This study provides empirical evidence that excessive bleeding, both heavy and prolonged, during the menopause transition is associated with women’s reports of feeling fatigue,” Harlow said.

Shifting hormone levels during perimenopause can cause menstrual cycles to become erratic, sometimes causing heavier and longer periods.

Estimates suggest up to 30% of perimenopausal women experience significant blood loss. Heavy bleeding is particularly prevalent among women who have a history of abnormal uterine bleeding, according to Harlow. Furthermore, many women develop fibroids at this age, which can contribute to more menstrual blood. 

According to Taylor, significant blood loss can lead to anemia, a condition that occurs when the body has low levels of red blood cells, which transport oxygen.

This condition, along with other common symptoms during perimenopause, like stress, night sweats, and sleep disruptions, can make someone feel sluggish. 

“The combination of less sleep and lower blood counts can lead to more fatigue,” Mary Jane Minkin, MD, a Yale School of Medicine gynecologist specializing in menopause, told Health.

Still, there’s a lot that scientists don’t yet understand about bleeding during perimenopause and how it affects women’s health and well-being. According to Harlow, more research is needed to know how menstrual changes during the menopause transition affect people with various gynecological conditions like fibroids, endometriosis, and polycystic ovarian syndrome (PCOS).

She’d like to see future studies investigate these questions. “Hopefully, these findings will encourage further evaluation of potential associations between menstrual bleeding and other symptoms of menopause such as disrupted sleep and cognitive fog,” Harlow said.

Harlow wants more physicians to recognize that abnormal uterine bleeding increases during perimenopause and ask about their patients’ menstrual history when evaluating fatigue.

But Taylor said it’s also up to individuals not to dismiss any menopausal symptoms as just a normal part of aging. “There is often a way to fix the problem,” he said.

Added Minkin: “We can usually help get the bleeding under control and help you get some more rest.”

If you’re experiencing heavy or prolonged bleeding, treatments like iron replacement, hormones, or removing fibroids may restore your energy levels and quality of life.

It can be difficult to find a healthcare provider who specializes in menopause and will listen to your concerns, Harlow said. As such, it’s crucial to try to find a care team that’s both knowledgeable and understanding.

“Both abnormal uterine bleeding and fatigue can impact quality of life and have serious health consequences, yet both conditions are treatable and need not simply be suffered,” she said.