A cycle that lasts longer than normal may be a side effect of nonhormonal medications or hormonal birth control, among other causes. A doctor can provide advice and help answer questions.

Humans, by nature, are creatures of habit. So it can feel alarming when a regular menstrual cycle suddenly becomes irregular.

If you’re experiencing a period that’s longer than usual, there’s probably a good explanation.

Before getting too worried, consider one of the causes below.

No two menstrual cycles are exactly the same. Some periods can last one day while others last a week, and the time in between periods can vary too.

The average cycle lasts 28 days — however, this doesn’t mean that something is wrong if yours doesn’t last that long.

Cycles can range in length from around 21 days to as long as 35 days.

Cycles shorter than 21 days typically signal that ovulation may have occurred earlier than normal or not at all.

Cycles longer than 35 days indicate that ovulation isn’t occurring or it’s occurring irregularly.

A period that’s longer than 7 days can also signal that ovulation hasn’t occurred.

Now that you know the basics, you’re probably wondering what’s causing your period to be longer than usual. There are many different plausible causes, and they’re typically manageable.

Certain nonhormonal medications

Some over-the-counter medications can interfere with period length.

Anticoagulants, such as aspirin, help prevent blood clots by prohibiting platelets from clumping together. Taken regularly, the medication can inadvertently prolong periods or cause heavier flows.

On the other hand, some nonsteroidal anti-inflammatory medications, such as ibuprofen and naproxen, can have the opposite effect and can make period flows lighter.

Antidepressants and epilepsy medication can also interfere with periods, causing them to be irregular, longer, or shorter. Some antidepressants can also cause heavier flows and painful cramps. With these medications, changes to your menstrual cycle should stop after a few months.

If any of these medications interfere for longer than 3 months, or if you’re concerned by the extent to which they’re affecting your cycle, ask a medical professional.

Hormonal birth control

Hormonal birth control, such as combination (estrogen and progestin), mini (progestin-only) pills, implants, rings, patches, shots, and IUDs, can affect period flows and cycle duration.

Some doctors actually prescribe the pill to those with a heavier flow, as the hormones can affect the growth of the uterine lining prior to menstruation.

Some people with IUDs report shorter periods or no periods whatsoever. This is mostly true for IUDs that contain hormones, while the copper IUD may cause longer or heavier periods.

While many forms of hormonal birth control reportedly cause lighter flows or shorter cycles, the birth control shot may cause prolonged menstrual flow (though in some people, it’s the opposite).

If you recently switched to a new form of hormonal birth control and you’re worried about the effect it’s having on your cycle, talk to the doctor who prescribed it. They should be able to explain if your side effects are cause for alarm.


Delayed or late ovulation can directly impact your period.

Ovulation usually occurs around the halfway point of a cycle, when the ovary releases a mature egg for fertilization.

Late ovulation is caused by a variety of things, such as stress, thyroid disease, PCOS, breastfeeding, and some medications.

This delay can cause the lining of the uterus to build up heavier than usual for a heavier, delayed period.

Other symptoms of late ovulation include:

  • a rise in basal (or resting) body temperature
  • side or lower abdominal pain
  • an increase in cervical discharge

Track your period to see if this problem continues. If it does, talk to a doctor about your next steps.

Emergency contraception

If you recently took a form of emergency contraception (sometimes referred to as the morning after pill), you could notice a change in your first period after ingestion.

The pill prevents pregnancy by delaying ovulation. This can disrupt the length of your normal menstrual cycle, causing irregularities in your next period including:

  • an early period
  • a late period
  • heavier flow
  • lighter flow
  • longer flow
  • more or less pain than usual

You could also notice some light spotting before your next period.

These symptoms should only disrupt the first period after taking the medication. Should they persist, seek out a doctor.

Abortion (first period after)

Both surgical abortions and medical abortions can affect menstruation.

First thing to know is that you may experience post-abortion bleeding. While it might look like your period, it’s not the same. This bleeding results from tissue releasing from the uterus.

The first period after an abortion can be shorter (if you had a surgical abortion) or longer (if you had a medical abortion) due to the process of your body returning to its normal hormone levels.

Pregnancy hormones can also stick around for a few weeks after your abortion, causing a delay in menstruation.

Other symptoms during this time include:

  • bloating
  • headaches
  • tenderness in the breasts and muscles
  • moodiness
  • fatigue

If your period doesn’t return 8 weeks after your procedure, see a doctor.

Early pregnancy

One of the earliest signs of pregnancy is a missed period. Light spotting or vaginal bleeding can also occur, mimicking the signs of a menstrual cycle.

Other period-like symptoms in early pregnancy include:

  • light cramping
  • fatigue
  • irritability
  • lower back pain

If you think you might be in the early stages of pregnancy, take an at-home pregnancy test.


Early miscarriages, which can happen before you even know you’re pregnant, can resemble a period with bleeding that gets heavier and lasts longer than a typical period.

The most common symptoms of an early miscarriage are cramping and bleeding, mimicking what would look like a heavy period.

Other symptoms include:

  • nausea
  • diarrhea
  • passing large fluids, such as blood clots or tissue, through the vagina

If you’re experiencing pain and excessive bleeding, and you think you’re having a miscarriage, set up an appointment with your doctor for an in-person physical exam.

Uterine polyps or fibroids

Uterine polyps happen when endometrial tissue grows on the lining of the uterus. Fibroids, similarly, are growths of fibrous tissue and muscle in the wall of the uterus.

Both fibroids and polyps can cause periods to be heavy, full of clots, and last longer than a week.

These tend to occur in people around 35 to 50 years old, or who are in perimenopause.

Other symptoms of fibroids include:

  • pelvic pressure
  • frequent urination or trouble urinating
  • constipation
  • backaches
  • leg pain

Other symptoms of polyps include spotting in between periods, vaginal bleeding after menopause, and infertility.

Treatment options for fibroids and polyps range from low-dose hormonal birth control to hysterectomies. A doctor will be able to best evaluate what’s going on, and in some cases they’ll be able to perform a hysteroscopy to get a better view inside the uterus.


Low thyroid hormone production can cause menstrual fluctuation, especially in younger individuals.

It can make periods heavier and more frequent, but it can also make them stop altogether.

Other symptoms that signal hypothyroidism include:

  • chills
  • fatigue
  • constipation
  • loss of appetite
  • sudden weight gain
  • dry hair or nails
  • depression


Polycystic ovary syndrome, or PCOS, happens when ovaries produce an excessive amount of male sex hormones called androgens.

This can alter periods, causing irregularity, light periods, or missed periods.

Other symptoms include:

  • acne
  • sudden weight gain
  • excessive body hair
  • dark patches near the neck, armpits, or breasts


This disorder happens when tissue similar to the tissue that forms the lining of your uterus grows outside of the uterus

One of the most common symptoms of endometriosis is abnormal periods. Periods can last longer than 7 days with heavy flows that require pads or tampons to be replaced every 1–2 hours.

Other symptoms of this include:

  • pain in the lower abdomen, pelvis, or lower back
  • painful sex
  • diarrhea
  • constipation
  • painful urination
  • a frequent need to urinate
  • infertility
  • fatigue

If you think you might have endometriosis, set up an appointment with your doctor for further evaluation.


This condition happens when the endometrial tissue that lines the uterus moves into the muscles of the uterus.

For some, there might be no symptoms of adenomyosis or there might be slight discomfort.

For others, there can be heavy menstrual bleeding, severe cramping, and chronic pelvic pain.

If you’re experiencing heavy bleeding alongside severe cramping during your periods, talk to a doctor. They’ll be able to determine if it’s adenomyosis through a pelvic exam or ultrasound.


Perimenopausal periods, which occur at the end of your reproductive years, can take the form of irregular periods, lighter flows, or light spotting.

As your hormones fluctuate, it’s also common to have heavier bleeding. This happens because the uterine lining builds with higher estrogen levels.

Perimenopause is normal for anyone who menstruates. It typically occurs between age 45 and 55.

Other symptoms include:

  • hot flashes
  • night sweats
  • difficulty urinating
  • difficulty sleeping
  • changes in sexual satisfaction
  • vaginal dryness

On rare occasions, prolonged menstrual bleeding and heavier flows may be cause for concern.

The following cases should be examined by a medical professional immediately.

Von Willebrand’s

This rare bleeding disease occurs when the body has low levels of Von Willebrand factor and cannot properly clot blood.

For menstruating individuals, this can result in long and heavy periods that include blood clots larger than one inch in diameter.

Other symptoms include:

  • excessive bleeding from an injury
  • nosebleeds that won’t stop
  • blood in your urine
  • anemia-related symptoms like fatigue and shortness of breath

Treatments include clot-stabilizing medications, oral contraceptives, and replacement therapy.


Hemophilia is a rare genetic disorder where the body is missing or has low levels of factor VIII or factor IX clotting proteins.

Although less prominent in females, they can still be “carriers” and symptoms are still possible.

This includes long, heavy periods, passing large clots, and needing to change a tampon or pad every 2 hours or less.

Other symptoms include:

  • unexplained or excessive bleeding from injury
  • large bruises
  • bleeding after vaccinations
  • joint pain
  • blood in your urine
  • sudden nosebleeds

Treatments for hemophilia include both plasma-derived factor concentrates and recombinant factor concentrates.

Cervical or uterine cancer

Gynecological cancers, including cervical and uterine cancer, are forms of cancer affecting female reproductive organs.

Anyone with female reproductive organs is at risk for gynecological cancer, and risk increases with age.

The HPV vaccine is recommended to help protect against cervical, vaginal, and vulvar cancers.

Abnormal bleeding, including heavy bleeding and irregular discharge, is a common symptom of cervical, ovarian, uterine, and vaginal cancer.

Pelvic pain or pressure is another symptom of uterine cancer.

Treatments for gynecological cancers include surgery, chemotherapy, and radiation.

Symptoms of gynecological cancers vary both by location of cancer and the person experiencing it. Heavy bleeding can be a symptom of many disorders, so this symptom alone doesn’t indicate cancer.

If your period lasts longer than a week, consider calling a doctor for advice. Depending on your symptoms, they may suggest setting up an in-person appointment for a physical exam.

On the other hand, if you think you’re showing symptoms of a rare cause or if you’re pregnant, see a doctor immediately.

If you experience severe heavy bleeding and you’re soaking through four or more pads and tampons in a 2-hour period, go to an emergency room right away.

Although it might be alarming to experience a sudden heavy flow or prolonged period, there are many causes that could explain your situation.

Monitor your period from month to month to see if your symptoms persist.

As always, it’s best to consult your doctor if you think anything might be up. They’re able to answer questions, discuss symptoms, perform pelvic exams, and perform ultrasounds if needed.

Jen Anderson is a wellness contributor at Healthline. She writes and edits for various lifestyle and beauty publications, with bylines at Refinery29, Byrdie, MyDomaine, and bareMinerals. When not typing away, you can find Jen practicing yoga, diffusing essential oils, watching Food Network, or guzzling a cup of coffee. You can follow her NYC adventures on Twitter and Instagram.