What Is a Normal Menstrual Cycle?
The average length of a menstrual cycle, defined as the number of days between periods, is 28 days on average across adults in all age groups. However, what’s considered normal varies between people and can vary between cycles as well.
What Causes Your Menstrual Cycle to Get Shorter?
There are multiple factors that can contribute to a shorter time between periods or shorter bleeding times, including birth control, pregnancy, medications, lifestyle factors, and more. While many reasons are not a cause for concern, there is a possibility of a serious health condition such as an ectopic pregnancy.
Age
Menstrual cycles naturally shorten with age, averaging 30 days for people under 19 and decreasing to around 28 days in the late 40s. This is largely due to changes in hormone levels, particularly a shorter follicular phase.
Extreme Exercise
Extreme exercise can shorten or disrupt the menstrual cycle by interfering with the balance of reproductive hormones. Athletes and people who regularly engage in intense training may experience irregular or missed periods, and starting a vigorous fitness routine suddenly can also cause these changes.
Weight Change
Significant weight changes, whether weight gain or sudden weight loss, can affect menstrual cycle length and regularity by disrupting hormonal balance.
Birth Control
Some types of birth control can affect the length of your period or cause amenorrhea (absence of a period). This includes pills, rings, intrauterine devices (IUDs), or injections.
Breastfeeding
Nursing (lactation) may cause skipped periods or shorter cycles. Nursing a baby suppresses reproductive hormones that usually stimulate ovulation. Lack of ovulation causes amenorrhea (not having a menstrual cycle).
Ectopic Pregnancy
An ectopic pregnancy is when a fertilized egg implants outside of the uterus. Unfortunately, a fetus cannot survive this type of pregnancy and it can cause severe health problems for the pregnant person. Ectopic pregnancies change how hormones behave, which in turn can affect periods.
Perimenopause
For people in their late 30s or 40s, a shorter period may indicate perimenopause—the time shortly before menopause. Hormones fluctuate during this time, causing people to skip their periods or experience irregular, heavier, or lighter cycles. The transition can last four to six years.
Stress
Stress causes the adrenal glands to release a hormone called cortisol, which can disrupt the endocrine system. This affects how your body communicates with reproductive hormones, affecting your menstrual cycle.
Medications
Medications such as non-steroidal anti-inflammatory medications (NSAIDs), thyroid hormones, and steroids can shorten period bleeding time. The same is true if you’ve stopped taking some medications such as blood thinners.
Other Medical Conditions
Certain medical conditions can cause irregular bleeding, shorter cycles, or breakthrough bleeding, including:
- Polycystic ovary syndrome (PCOS)
- Endometriosis
- Fibroids
- Adenomyosis
- Endometrial hyperplasia
- Ovarian cancer
When to See a Healthcare Provider
Contact your healthcare provider if you experience the following:
- Irregular periods after established cycles
- Periods that occur every 21 to 24 days or less
- A cycle longer than 35 to 38 days
- Spotting or bleeding when it’s not your period
- A skipped period for three months in a row and are not pregnant or nursing
- You haven’t started your period by age 15 or within three years of breast growth beginning
- Other changes in periods that indicate you should call your healthcare provider
Getting a Diagnosis
Your healthcare provider will begin by taking your medical history and asking about your cycle and any symptoms. If needed, they will perform a pelvic exam. A pregnancy test may be ordered if you’re of childbearing age. They may also suggest blood tests to check your ovaries, endocrine system, or hormones.
Conclusion
A shorter menstrual cycle or bleeding period can be due to a number of causes, including pregnancy, birth control, health conditions, medications, stress, and more. You should contact a healthcare provider if your periods become irregular after being consistent or if they occur every 21 to 24 days or less. Additionally, seek medical advice if you experience other concerning symptoms like heavy bleeding, dizziness, or clots larger than a quarter.
