If your period or menstrual cycle suddenly becomes shorter than usual, here are eight possible reasons why—and what they might mean for your health.
One person may have a 28-day menstrual cycle, while another consistently experiences a 35-day cycle. There is no single “normal” cycle—everybody is unique. However, if your period suddenly becomes shorter than usual, it may be worth paying attention to. So, what could be causing this?
Reasons Your Period Might Be Shorter
The menstrual phase, which is the period during which you bleed, can last anywhere from two to seven days. As long as your period falls within this range, doctors generally consider it “normal,” so there’s no need to worry. However, if your usual period lasts five days and suddenly shortens to just two, it’s worth exploring possible reasons.
1. You Exercise a Lot
In most cases, exercise doesn’t have a significant impact on the menstrual cycle, says gynecologist Jennifer Lew in an interview with mindbodygreen. However, intense or high-level physical activity can disrupt your cycle, sometimes leading to shorter or even missed periods.
Exercise affects the hypothalamic-pituitary axis, which is a hormonal feedback system involving the brain and ovaries. “The hypothalamus regulates your cycle, and if you’re training at a very intense level, your body might perceive it as an unsuitable time for reproduction, leading to disruptions in ovulation,” explains gynecologist Christine Greves.
As a result, “your body may still build up uterine lining, but due to a lack of hormonal signals, it may not shed as expected,” adds gynecologist Wendie Trubow. Additionally, excessive exercise can suppress estrogen levels, which can lead to shorter periods because less uterine lining is built up, resulting in lighter and shorter bleeding.
2. You’re Experiencing High Stress
Several studies have shown that stress can impact the menstrual cycle. “Extreme stress can affect your cycle by delaying or disrupting ovulation,” Lew explains.
This is largely due to cortisol, the stress hormone. “When you’re stressed, your body produces cortisol. Depending on how your body responds, this can lead to a lighter or shorter period—or even cause you to skip it entirely,” says gynaecologist Swapna Kollikonda to the Cleveland Clinic.
3. You’re Breastfeeding
It can take weeks or even months for your period to return after childbirth, says Greves. Breastfeeding can further delay its return. “Breastfeeding affects your hormones and ovulation—your hormone levels are not entirely normal during this time,” she explains.
The hormone prolactin, which stimulates milk production, can also suppress or shorten your menstrual cycle.
4. You’ve Started a New Medication
Medications often have side effects, and some can impact the menstrual cycle. Greves notes that hormonal birth control, IUDs, thyroid medications, antidepressants, and epilepsy treatments may shorten periods. However, not everyone experiences this side effect. “It largely depends on how your body responds to the medication,” she says.
5. You’re in Perimenopause
Perimenopause refers to the years leading up to menopause. If you’re in your 40s, your ovaries start producing less estrogen, Greves explains. This can lead to shorter and lighter periods. Lew adds that menstrual cycles may also become more irregular, with longer gaps between them.
Reasons Your Menstrual Cycle Might Be Shorter
Your menstrual cycle consists of four phases:
- Menstrual phase – The time when you bleed.
- Follicular phase – Begins during menstruation and lasts about two weeks until the ovaries release a new egg. During this phase, the brain produces follicle-stimulating hormone (FSH) to help the egg mature.
- Ovulation phase – When ovulation occurs.
- Luteal phase – Estrogen and testosterone levels drop, while progesterone increases.
While many people assume a menstrual cycle lasts 28 days, this isn’t true for everyone. A cycle can range between 21 and 45 days. If your cycle has always been 21 days, there’s no cause for concern. However, if your usual cycle is 40 days and suddenly drops to 25, that could indicate an underlying issue.
Poor Ovulation
According to obstetrics and gynaecology professor Mary Jane Minkin, the most common reason for a shorter cycle is poor ovulation.
“When ovulation occurs—typically mid-cycle—the ovary transforms the follicle (the area where the egg was released) into a progesterone-producing structure. Progesterone then prepares the uterine lining for a fertilized egg to implant,” she explains.
If fertilization doesn’t happen, the progesterone-producing follicle breaks down, progesterone levels drop, and menstruation begins. “Anything that disrupts ovulation can lead to lower progesterone levels and, consequently, a shorter cycle,” Minkin adds.
Just like shorter periods, this can occur due to ageing, postpartum hormonal shifts, or breastfeeding.
“If you experience one short cycle, I wouldn’t worry,” says Minkin. “But if it keeps happening, it may be worth checking in with your doctor or gynaecologist.”
This article was originally published by Vivian Seljee on the Marie Claire Netherlands website.
Translated and syndicated for Marie Claire Nigeria by Tobi Afolabi.
