Reasons Your Period Is Shorter Than Normal

Menstrual cycles are a monthly experience that most women go through. Women who track their period may notice that they have a shorter cycle. This could be caused by birth control, pregnancy, and more. This article reviews possible reasons for a shorter cycle, when to notify your healthcare provider, and how they may reach a diagnosis when necessary.

Normal vs. Short Period Cycle

A woman’s menstrual cycle is the time between each period (vaginal or uterine bleeding). The days are counted from day one of bleeding from each period to the next. Depending on when a woman ovulates, most cycles last 21 to 35 days. Bleeding times average three to seven days and often shorten as you age. A short period cycle is less than 21 days.

Causes

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 serious health conditions such as an ectopic pregnancy. 

It’s important to monitor your cycle to alert your healthcare provider when necessary. This helps them identify and treat any underlying health concerns early.

Birth Control

Some 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. When changes occur, they are usually within a few months after starting birth control. Changing the brand or type of birth control can also affect the length of your menstrual cycle. 

Pregnancy

If a woman is unaware of her pregnancy, she may mistake implantation bleeding for her period. Implantation bleeding is when the embryo first burrows into the uterus, usually about 10-14 days after conceiving a baby. It typically occurs around the same time as your period but is lighter than menstrual bleeding.

Ectopic Pregnancy

An ectopic pregnancy is when a fertilized egg implants outside of the uterus. Unfortunately, a baby can not survive this type of pregnancy, and it can cause severe health problems for the mother. Ectopic pregnancies change a woman's hormones which can affect periods.

Miscarriage

A miscarriage is a spontaneous pregnancy loss that happens before 20 weeks. Most occur within the first 12 weeks of pregnancy and sometimes before a person knows they're pregnant. As with other pregnancies, hormones are disrupted and can cause a change in periods during and after miscarriages.

Breastfeeding

Breastfeeding 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). As breastfeeding time and amount decrease, women typically start having cycles again. However, cycles may remain shorter until the baby is weaned (no longer breastfeeding).

Perimenopause

For women in their last 30s or 40s, a shorter period may indicate perimenopause, or the time before menopause. Hormones fluctuate during this time, causing women to skip their period 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 such as estrogen, affecting your menstrual cycle.

Medications

Medications such as non-steroidal anti-inflammatory medications (NSAIDs), antidepressants, thyroid hormones, and steroids can shorten period bleeding time. The same is true for women who’ve stopped taking some medications such as blood thinners. While this is not an extensive list, other examples of medicines that may cause period changes include:

• Antidepressants 
• Seizure medications (anticonvulsants)
• Chemotherapy
• Antifibrinolytics (prevents bleeding)

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 and a pregnancy test is typically ordered for women of childbearing age. They may also suggest blood levels to check your ovaries, endocrine system, or hormones. 

When necessary, the healthcare team may also suggest imaging tests such as a transvaginal ultrasound, computed tomography (CT) scan, or magnetic resonance imaging (MRI) of the abdomen, pelvis, and head. 

When to Seek Medical Attention

Contact your healthcare provider if you experience the following:

• Irregular periods after established cycles
• Periods that occur every 21-24 days or less  
• A cycle longer than 35-38 days
• Spotting or bleeding when it’s not your period
• A skipped period for three months in a row and are not pregnant or breastfeeding
• You’ve not 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 include:

• Heavier or longer-lasting periods
• Bleeding after menopause
• Period bleeding lasting longer than eight days
• Bleeding through one or more tampons or pads every one to two hours
• Dizziness
• Lightheadedness
• Weakness
• Menstrual blood clots larger than a quarter

Summary

Menstrual cycles or periods are a monthly experience that most women go through. Sometimes women notice that they are getting periods more often or their bleeding time is shorter. This can be due to a number of causes, including pregnancy, birth control, health conditions, medications, stress, and more. 

A Word From Verywell 

Occasional changes in your period are normal and can happen due to stress, an unhealthy diet, changing hormones, or too much exercise. However, your healthcare provider needs to know you are experiencing a shortened menstrual cycle so they review your medications and rule out any underlying conditions.