What Causes a Late Period?

By Jennifer Nadel, MD
Medically reviewed checkmarkMedically reviewed
June 21, 2022

Whether you’re just starting your period as a young adolescent or well into your menstrual cycle days, many people experience certain period symptoms. The symptoms vary from person to person. 

On average, a menstrual period lasts between four and seven days, occurring every 28 days.

The range of what’s considered to be a normal cycle is anywhere between 21 and 35 days. 

Some people experience regular, predictable periods, while others experience irregular or missed periods that make it difficult to predict. 

Irregular menstrual cycles occur in roughly 14-25% of people of childbearing age and can occur for a number of reasons. This article will cover the causes of late periods and what to do when your period is late.

What’s Considered a Late Period?

Missing a period can be a cause for concern but often can be nothing to worry about. 

Amenorrhea refers to when you don’t have a period. It is also described as an absence of menstruation, often for one, two, or even three or more cycles. 

Primary amenorrhea is when menstruation fails to begin at puberty. Secondary amenorrhea is when you’ve already experienced periods that were normal and regular but are now irregular. 

A late period refers to when your period comes five or more days late compared to your normal menstrual cycle.

A missed period refers to no menstrual cycle for more than six weeks.

Concerned about a late period? Chat with a medical provider through K Health.

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Causes Of Late Period

Stress

High stress levels can cause a variety of physical health issues, including late periods. 

Minor stress from everyday life likely won’t affect your period.

But if you’re experiencing high levels of stress, this can affect the regularity of your menstrual periods.

High stress activities or events can include:

  • Death of a loved one
  • School exams
  • Job loss or a partner losing a job
  • Other major life events, such as a wedding, moving, etc. 

Stress affects everyone’s body and brain differently, so you won’t necessarily experience the same symptoms as someone else with high stress levels. 

Low Body Weight

Being 10% or more under normal body weight (excessively low body weight) can interrupt many hormonal functions in the body, potentially stopping ovulation.

People with an eating disorder, such as anorexia or bulimia, often stop having menstrual periods due to abnormal hormone changes. 

Polycystic Ovary Syndrome (PCOS)

PCOS is a hormonal disorder that causes infrequent or prolonged menstrual periods or excess male hormone (androgen) levels.

Another sign is polycystic ovaries, where the ovaries develop small collections of follicles around the eggs and fail to release eggs regularly. 

Many people with PCOS have irregular, late, or missed periods. 

Signs and symptoms of PCOS may include:

Extreme Exercise

Exercising too much can cause you to miss menstrual periods or stop periods entirely. 

Irregular or missed periods are more common in athletes and people who engage in intense exercise regularly. 

If you don’t typically work out regularly and then begin an intense fitness routine, your period could become irregular or stop.

Birth Control

Changes in your form of birth control can cause missed periods.

If you’ve recently switched to a different type of birth control, the different hormone levels can lead to a missed period as your body adjusts to the hormonal change. 

Hormone imbalances can cause you to miss your period while taking birth control pills

If you’ve been taking your birth control pills regularly but still miss a period, take a pregnancy test if you are sexually active. 

If you continue to have missed or irregular periods, see a doctor for further investigation of the cause.

Birth control pills are 99% effective, so there’s still a small chance you can get pregnant while on birth control.

In the event that birth control doesn’t work, it’s usually because it wasn’t used correctly.

Examples might include:

  • When you forget to take your birth control at the same time every day
  • When you’re sick, and your birth control comes out in your vomit
  • When you have severe diarrhea
  • The timing is wrong for your pill cycle
  • You have interactions with other medication

Early Peri-Menopause

Peri-menopause refers to the time around menopause when the body is making the natural progression to menopause and the end of reproductive years. 

Irregular periods can be a symptom of peri-menopause because as ovulation becomes more unpredictable, the length of time between menstrual periods can change. 

The level of flow may change as well, and you may skip some periods while in peri-menopause. 

Once you’ve gone 12 consecutive months without a menstrual period, you’ve reached menopause, and the perimenopause period is over.

Medications

Certain medications can cause late or missed periods, including some types of:

  • Antipsychotics
  • Cancer chemotherapy
  • Antidepressants
  • Blood pressure drugs
  • Allergy medications

Change In Your Schedule

Changes in your daily routine can also affect how regularly you experience menstrual periods. 

Changes in your sleep or travel schedules may affect period regularity as well.

For example, switching to a night shift at work or traveling to another time zone may prevent your cycle from starting.

Disruptions to your circadian rhythm can play a role in irregular menstrual periods. 

Breastfeeding

If you’re breastfeeding your child, missed periods are completely normal. Lactational amenorrhea refers to the phase that disrupts the regularity of your menstrual cycle.

After a few months, your period should be back to a regular cycle. 

Recent Weight Changes

If you’re not consuming an appropriate number of calories or you’re lacking certain nutrients, this can affect the hormones responsible for causing a menstrual period. 

Missed or irregular periods can often occur in elite athletes. 

It can also occur in people with eating disorders such as anorexia nervosa or bulimia.

Obesity

Being overweight can affect your menstrual cycle and its regularity. 

When overweight, your body can produce too much estrogen, one of the sex hormones that regulate the female reproductive system.

Excess estrogen can affect the regularity of your periods and can also cause missed periods.

Your doctor may refer you to a dietitian if you’re overweight and it’s affecting your periods. 

Chronic Diseases

Type 1 and type 2 diabetes can cause irregular periods if uncontrolled.

If you have your diabetes under control, it’s more likely that you’ll begin to experience more regular periods. 

Pelvic inflammatory disease (PID), an infection of the reproductive organs, can result in irregular periods. PID is most frequently caused by a sexually transmitted infection (STI). 

Recently Started Periods

It’s rare for a young person to begin their period and immediately have a regular menstrual cycle. It usually takes a few years to become more regular.

Your period will likely become more regular in your late teens or early 20s.

Thyroid Issues

The thyroid is regulated by the hypothalamus and is responsible for hormones that control menstruation. 

Both an overactive thyroid (hyperthyroidism) and an underactive thyroid (hypothyroidism) can cause irregular periods. 

Hyperthyroidism can cause your thyroid to make more thyroid hormone than the body needs and can cause fewer and lighter menstrual periods than normal. 

Pregnancy

A missed period is one of the most common signs of pregnancy.

You may experience slight bleeding or spotting when you’re pregnant, among other symptoms. You will likely experience a missed period. 

A period occurs when the lining of the uterus sheds off because a fertilized egg didn’t implant there.

If the uterus is implanted with a fertilized egg, the uterine lining won’t shed, which is why periods stop when you’re pregnant.

Concerned about a late period? Chat with a medical provider through K Health.

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What to Do If Your Period Is Late (But Not Pregnant)

Treatment of late periods depends on the cause, but may include:

  • Hormonal changes/ treatment (progesterone supplements)
  • Birth control pills (to prevent ovulation)
  • Dietary changes (to increase or decrease body weight)

Talk to your doctor about how to treat your irregular periods. Treatment will depend on the cause of your irregular or missed periods. 

When to See a Medical Provider

See a medical provider after three missed periods or three dramatically different periods if you’ve already ruled out pregnancy as a cause.

Other scenarios include:

  • You’re 15 years old and haven’t experienced your first menstrual period
  • You get irregular periods after having normal menstrual cycles
  • Your period occurs more frequently than every 24 days or less often than every 38 days

How K Health Can Help

Did you know you can get affordable primary care with the K Health app?

Download K to check your symptoms, explore conditions and treatments, and if needed text with a doctor in minutes. K Health’s AI-powered app is HIPAA compliant and based on 20 years of clinical data.

Frequently Asked Questions

How Much Delay is Normal in Periods?
If your period is a day or two late, don’t worry. Your menstrual cycle is the length of time between day one of your period and day one of your next period. On average, cycles are 24 to 38 days long, so having menstrual cycles that differ by a few days is most likely nothing to worry about.
When Should I Worry About a Late Period?
See your doctor to determine the cause of your missed periods if you’re experiencing any of the following: You’ve missed more than one period in a row It’s been more than 38 days since your last period You’re normally regular, and your period is more than three days late You’re experiencing other symptoms such as pain, excessive bleeding, or fever
What Causes a Delayed Period?
Delayed or missed periods can be due to: Birth control Breastfeeding Changes in your schedule Chronic diseases Early peri-menopause Extreme exercise Low body weight Medications Obesity Polycystic Ovary Syndrome (PCOS) Pregnancy Recent weight changes Recently started periods Stress Thyroid issues
Should I Worry if My Period is 5 Days Late?
Having a menstrual cycle that differs by a few days is most likely nothing to worry about. Delayed periods can be the result of non-serious issues like extreme exercise, stress, or a recent weight change. However, see your doctor if it’s been more than 38 days since your last period or you’re experiencing symptoms such as pain, excessive bleeding, or fever.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Jennifer Nadel, MD

Dr. Jennifer Nadel is a board certified emergency medicine physician and received her medical degree from the George Washington University School of Medicine. She has worked in varied practice environments, including academic urban level-one trauma centers, community hospital emergency departments, skilled nursing facilities, telemedicine, EMS medical control, and flight medicine.