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:
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.
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:
There are certain factors that can influence menstrual bleeding, including:
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.
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.
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.
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.
There are certain symptoms that can occur with heavy periods that require urgent evaluation by your healthcare provider. These include:
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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