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Heavy menstrual period? How to identify if there’s a problem

Medically reviewed by Neka Miller, PhD on March 27, 2020. Written by Libby Pellegrini. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Read more: What is normal menstrual bleeding and abnormal menstrual bleeding? | What causes variations in menstrual bleeding? | What does it mean when your period is really heavy? | When should I be concerned about a heavy period?

Menstruation is a fact of life for most women of childbearing age. During the menstrual cycle, which involves a monthly ebb and flow of estrogen and progesterone hormones, a woman’s uterus prepares for pregnancy. If conception does not occur, the uterus discards its efforts. The bleeding that occurs during a menstrual cycle is the shedding of the lining of the uterus; the uterine lining passes through the cervix and out of the vagina, appearing as blood.

It can be hard to know what’s considered “normal” when it comes to your menstrual cycle. Menstruation can look very different from one woman to another. However, there are some established clinical guidelines when it comes to what’s considered heavy menstrual bleeding.

Read on to learn more, including:

  • What normal menstrual bleeding or spotting looks like
  • What heavy menstrual bleeding looks like
  • When is heavy menstrual bleeding an emergency

Because hormones directly affect your menstrual cycle, imbalances can lead to heavy menstrual bleeding. Check your levels of 10 key hormones from the convenience of home with the Everlywell Women’s Hormone Test.


What is normal menstrual bleeding and abnormal menstrual bleeding?

The average menstrual cycle is 28 days long, from the first day of a woman’s period to the start of the next period. Generally, periods last from four to five days, although they can be shorter or longer.

When it comes to blood loss, the average amount of blood that is lost during one menstrual cycle is less than 60 milliliters, or about 2 tablespoons, although many women may bleed less than this, and many women will bleed more.

The definition of heavy menstrual bleeding, or an abnormally large loss of blood, is more than 60-100 milliliters per cycle (more than about 5 and a half tablespoons). This can occur because a woman loses a large amount of blood at once, or bleeds for an excessively long time, or both.

Your menstrual bleeding is also considered abnormal if you experience the following:

  • Saturating more than one pad or tampon every one to two hours
  • Passing large blood clots larger than 1 inch in diameter (the size of a quarter)
  • Prolonged menstrual bleeding that lasts longer than seven days
  • Needing to double up on pads or tampons or change them during the night due to heavy bleeding

What causes variations in menstrual bleeding?

There are certain factors that can influence menstrual bleeding, including:

  • Birth control. Most oral contraceptive pills tend to normalize your menstrual flow. However, certain birth control methods, such as a copper IUD, can result in abnormal bleeding (such as increased menstrual bleeding).

  • Exercise. With increased exercise, hormone levels tend to shift. As testosterone rises with more physical activity, some women can see a decrease in their menstrual flow. In cases of extreme training, some women will stop getting menstrual periods altogether. This is known as amenorrhea.

  • Age. As age increases, menstrual flow tends to change as well. As menopause approaches, periods tend to gradually slow, and become more infrequent, although there may be fluctuations. Some women will have heavy menstrual bleeding as they approach menopause.

  • Diseases. Certain medical conditions can impact your menstrual flow as well. For example, a condition known as polycystic ovarian syndrome (PCOS) can cause decreased menstruation.

  • Hormonal fluctuations. Changes in your levels of various hormones—such as estrogen, progesterone, LH, FSH, testosterone, cortisol or thyroid hormone—can affect your menstrual cycle. The Everlywell at-home Women’s Health Test gives you a comprehensive look at 10 key hormones so you can check in on your personal hormone balance from the comfort of your own home. If you do have a hormone imbalance, you can speak with your healthcare provider about relevant medical treatment that may help with hormone health.

What does it mean when your period is really heavy?

If you find yourself wondering, “Why is my period so heavy?” you may be curious about what causes heavy menstrual periods. There are many possible causes of heavy periods. Here are some of the most common.


An infection of the reproductive organs caused by an untreated sexually transmitted infection, such as gonorrhea or chlamydia, can cause an inflammatory condition called pelvic inflammatory disease (PID). With this condition, women may experience pelvic pain, abnormal vaginal discharge, and heavy vaginal bleeding. It can be diagnosed with a pelvic exam and treated with antibiotic medications.

Uterine fibroids

Many women will experience heavy or irregular bleeding because of uterine fibroids, which are benign tumors that can grow in the uterus. These tend to swell with the surge of hormones during the menstrual cycle, and then bleed when conception does not occur, causing an abnormal amount of blood loss. Related conditions include uterine polyps and adenomyosis, in which uterine tissue grows into the muscular lining of the uterus—also causing heavy menstrual bleeding.

Bleeding disorders

Certain bleeding disorders can also cause abnormal vaginal bleeding. The most common bleeding disorder, von Willebrand disease, affects up to 1% of Americans. In this condition, the body’s ability to form blood clots is decreased, so when menstrual bleeding occurs it can be very heavy and prolonged.

There are other disorders that can cause excessive bleeding, and many are inherited. If heavy menstrual bleeding seems to run in a family, it may be related to genetics.


Certain medications can cause heavier menstrual bleeding. If you experience a change in your menstrual bleeding after starting a new medication, make sure to check in with your healthcare provider.


Abnormal menstrual bleeding may be related to cancer, specifically cervical or uterine cancer. If you experience a sudden change in your menstruation (such as excessive bleeding), paired with pelvic pain or weight loss, make sure to follow up with your healthcare provider immediately.

Ectopic pregnancy

When a pregnancy occurs outside of the uterus, such as in the fallopian tubes or on an ovary, it is called an ectopic pregnancy. With an ectopic pregnancy, a woman will have a positive pregnancy test but a pregnancy will typically not be seen in the uterus on ultrasound.

Ectopic pregnancies that go undetected can rupture, causing pain and severe vaginal bleeding. This is a medical emergency that is potentially fatal; contact your healthcare provider immediately if you have a positive pregnancy test and abdominal or pelvic pain with heavy bleeding.

When should I be concerned about a heavy period?

There are certain symptoms that can occur with heavy periods that require urgent evaluation by your healthcare provider. These include:

  • Shortness of breath. Shortness of breath can be a symptom of anemia, a condition in which so much blood is lost that the body has a low hemoglobin level and cannot keep up with its replacement of red blood cells. This can also cause severe tiredness, lightheadedness, or dizziness. If the anemia is severe enough, a woman may require a blood transfusion.

  • Bleeding after menopause. If menstrual bleeding starts after it has stopped (after menopause), this could be a sign of a more serious condition, such as a malignancy.

  • Pregnancy. If you have heavy vaginal bleeding and you have had a positive pregnancy test, make sure to contact your healthcare provider immediately.

  • Pain. Heavy menstrual periods that occur with severe pain could be a sign of a more urgent condition. However, even if they aren’t caused by an urgent condition, severe pain and heavy menstrual bleeding can significantly impact your daily functioning and quality of life—so if you’re experiencing this make sure to talk with your healthcare provider.

Check for imbalances in 10 key hormones—which can affect menstrual bleeding—with the at-home Women's Hormone Test, which gives you easy-to-read results you can share with your healthcare provider.

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  1. About Menstruation. National Institutes of Health. [URL]( Accessed March 27, 2020.
  2. Fraser IS, Warner P, Marantos PA. Estimating menstrual blood loss in women with normal and excessive menstrual fluid volume. Obstet Gynecol. 2001;98(5 Pt 1):806–814. doi:10.1016/s0029-7844(01)01581-2
  3. Heavy Menstrual Bleeding. Centers for Disease Control and Prevention. [URL]( Accessed March 27, 2020.
  4. What causes menstrual irregularities? National Institutes of Health. [URL]( Accessed March 27, 2020.
  5. Pelvic Inflammatory Disease (PID) - CDC Fact Sheet. Centers for Disease Control and Prevention. [URL]( Accessed March 27, 2020.
  6. Vannuccini S, Petraglia F. Recent advances in understanding and managing adenomyosis. F1000Res. 2019;8:F1000 Faculty Rev-283. Published 2019 Mar 13. doi:10.12688/f1000research.17242.1
  7. What is von Willebrand Disease? Centers for Disease Control and Prevention. [URL]( Accessed March 27, 2020.
  8. Menorrhagia (heavy menstrual bleeding). Mayo Clinic. [URL]( Accessed March 27, 2020.
  9. Ectopic pregnancy. Mayo Clinic. [URL]( Accessed March 27, 2020.
  10. Bleeding during pregnancy. Mayo Clinic. [URL]( Accessed March 27, 2020.
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