Heavy Menstrual Bleeding: What Causes It and When to Seek Help

How heavy is too heavy? A practical way to know

Everyone's baseline differs, which makes 'heavy' somewhat subjective — but clinically recognized benchmarks help. Needing to change a pad or tampon every hour for two or more consecutive hours is considered heavy. Passing blood clots larger than a quarter is another indicator. Additional signs include: periods lasting longer than seven days, needing to use both a pad and tampon simultaneously, waking at night to change protection, or canceling plans due to bleeding.

Anemia (low iron) from chronic blood loss is a common downstream consequence 1Ref 1Leung AKC, Lam JM, Wong AHC, Hon KL, Li X (2024).Iron Deficiency Anemia: An Updated Review.Iron deficiency anemia is a common consequence of chronic heavy menstrual blood loss; fatigue, paleness, and shortness of breath are key symptoms. Fatigue, paleness, and shortness of breath alongside heavy periods are meaningful symptoms that should not be dismissed 1Ref 1Leung AKC, Lam JM, Wong AHC, Hon KL, Li X (2024).Iron Deficiency Anemia: An Updated Review.Iron deficiency anemia is a common consequence of chronic heavy menstrual blood loss; fatigue, paleness, and shortness of breath are key symptoms.

What causes heavy periods?

Uterine fibroids are noncancerous growths within or attached to the uterine wall and are among the most frequent structural causes of heavy periods, particularly in people in their 30s and 40s. Fibroids are significantly more common and more severe in Black women, who are also more likely to experience delayed diagnosis 2Ref 2American College of Obstetricians and Gynecologists (2019).Screening and Management of Bleeding Disorders in Adolescents With Heavy Menstrual Bleeding: ACOG Committee Opinion, Number 785.Bleeding disorders including von Willebrand disease are an underrecognized cause of heavy menstrual bleeding, particularly in adolescents; ACOG recommends coagulation screening; racial disparities in fibroid diagnosis and hormonal treatment options are also addressed in this guidance.

Hormonal imbalance — particularly a disruption in the estrogen-to-progesterone ratio — causes the uterine lining to build up more than usual and shed heavily. This is common in teenagers whose hormonal axis is still maturing and in the years approaching menopause 2Ref 2American College of Obstetricians and Gynecologists (2019).Screening and Management of Bleeding Disorders in Adolescents With Heavy Menstrual Bleeding: ACOG Committee Opinion, Number 785.Bleeding disorders including von Willebrand disease are an underrecognized cause of heavy menstrual bleeding, particularly in adolescents; ACOG recommends coagulation screening; racial disparities in fibroid diagnosis and hormonal treatment options are also addressed in this guidance.

Uterine polyps — small, usually benign growths of the uterine lining — can cause heavier-than-usual bleeding and are detected by pelvic ultrasound.

Adenomyosis is a condition in which the uterine lining grows into the muscular wall of the uterus, causing heavy and often painful periods 3Ref 3American College of Obstetricians and Gynecologists (2010).Management of Endometriosis: ACOG Practice Bulletin, Number 114 (Reaffirmed 2022).Adenomyosis and endometriosis are structural causes of heavy, painful periods; endometrial hyperplasia and uterine cancer must be considered in the differential when heavy or irregular bleeding is present. It is frequently underdiagnosed.

Bleeding disorders, such as von Willebrand disease, are an underrecognized cause of heavy periods, especially in people who have had heavy periods since adolescence 2Ref 2American College of Obstetricians and Gynecologists (2019).Screening and Management of Bleeding Disorders in Adolescents With Heavy Menstrual Bleeding: ACOG Committee Opinion, Number 785.Bleeding disorders including von Willebrand disease are an underrecognized cause of heavy menstrual bleeding, particularly in adolescents; ACOG recommends coagulation screening; racial disparities in fibroid diagnosis and hormonal treatment options are also addressed in this guidance. A clotting disorder workup is recommended when this pattern is present.

Thyroid dysfunction — particularly hypothyroidism — can make periods heavier and more prolonged 4Ref 4Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Hypothyroidism can cause heavier and more prolonged menstrual periods; TSH testing is an appropriate step in the workup of heavy menstrual bleeding. TSH testing is a standard part of the workup.

Anticoagulant medications (blood thinners) and certain other drugs can substantially increase menstrual blood loss.

Which causes require prompt attention?

While most heavy menstrual bleeding has a benign cause, some require evaluation without delay.

Endometrial hyperplasia — abnormal thickening of the uterine lining — can precede endometrial cancer, particularly in older adults or those with a history of irregular cycles, obesity, or estrogen-only hormone therapy 3Ref 3American College of Obstetricians and Gynecologists (2010).Management of Endometriosis: ACOG Practice Bulletin, Number 114 (Reaffirmed 2022).Adenomyosis and endometriosis are structural causes of heavy, painful periods; endometrial hyperplasia and uterine cancer must be considered in the differential when heavy or irregular bleeding is present.

Endometrial cancer, while not the most common cause, is a possibility clinicians screen for when heavy or irregular bleeding develops — especially after menopause 3Ref 3American College of Obstetricians and Gynecologists (2010).Management of Endometriosis: ACOG Practice Bulletin, Number 114 (Reaffirmed 2022).Adenomyosis and endometriosis are structural causes of heavy, painful periods; endometrial hyperplasia and uterine cancer must be considered in the differential when heavy or irregular bleeding is present.

Pregnancy complications (miscarriage or ectopic pregnancy) can also present as heavy or unusual bleeding and should be ruled out in anyone of reproductive age.

How are heavy periods evaluated and treated?

A clinician will typically start with a history and physical exam, then order blood tests (complete blood count to check for anemia 1Ref 1Leung AKC, Lam JM, Wong AHC, Hon KL, Li X (2024).Iron Deficiency Anemia: An Updated Review.Iron deficiency anemia is a common consequence of chronic heavy menstrual blood loss; fatigue, paleness, and shortness of breath are key symptoms, TSH for thyroid function 4Ref 4Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Hypothyroidism can cause heavier and more prolonged menstrual periods; TSH testing is an appropriate step in the workup of heavy menstrual bleeding, and a coagulation panel if a bleeding disorder is suspected 2Ref 2American College of Obstetricians and Gynecologists (2019).Screening and Management of Bleeding Disorders in Adolescents With Heavy Menstrual Bleeding: ACOG Committee Opinion, Number 785.Bleeding disorders including von Willebrand disease are an underrecognized cause of heavy menstrual bleeding, particularly in adolescents; ACOG recommends coagulation screening; racial disparities in fibroid diagnosis and hormonal treatment options are also addressed in this guidance) and a pelvic ultrasound to look for fibroids, polyps, or endometrial thickening. A pregnancy test is standard before any imaging or procedures in reproductive-age people.

Treatment depends on the underlying cause and on fertility goals. Hormonal options — including the combined pill, progestin-only pill, or hormonal IUD — are effective at reducing flow for many causes 2Ref 2American College of Obstetricians and Gynecologists (2019).Screening and Management of Bleeding Disorders in Adolescents With Heavy Menstrual Bleeding: ACOG Committee Opinion, Number 785.Bleeding disorders including von Willebrand disease are an underrecognized cause of heavy menstrual bleeding, particularly in adolescents; ACOG recommends coagulation screening; racial disparities in fibroid diagnosis and hormonal treatment options are also addressed in this guidance. Non-hormonal medications also exist. For structural causes like fibroids or polyps, a minimally invasive procedure may be recommended. A clinician will help map the options to your specific situation.