Heavy periods — medically termed heavy menstrual bleeding (HMB) or menorrhagia — are one of the most common gynecologic complaints, affecting approximately 1 in 5 women of reproductive age 1. The causes of heavy periods are varied and include both structural abnormalities (such as fibroids and polyps) and non-structural causes (such as hormonal imbalances and bleeding disorders).
While many women accept heavy periods as simply a feature of their body, heavy menstrual bleeding can significantly impact quality of life and may indicate an underlying condition that deserves evaluation. Understanding the common causes is the first step toward getting appropriate care. See the women's health hub for a full library of related gynecological guides.
What Counts as Heavy Menstrual Bleeding?
Clinically, heavy menstrual bleeding is defined as blood loss exceeding 80 mL per menstrual cycle — a volume difficult to measure directly.
In practice, clinicians and patients use practical indicators: soaking a pad or tampon every hour for several consecutive hours; needing to double up on protection; passing blood clots larger than a quarter; bleeding that lasts longer than 7 days; or bleeding that is severe enough to interfere with daily activities such as work, exercise, or social commitments 1.
Any of these patterns warrants clinical evaluation, particularly if they represent a change from your normal pattern.
Structural Causes of Heavy Periods
Uterine Fibroids
Uterine fibroids (leiomyomas) are benign muscle tumors of the uterus and are among the most common causes of heavy menstrual bleeding. They affect up to 70–80% of women by age 50, though not all fibroids cause symptoms 2. Submucosal fibroids — those that project into the uterine cavity — are most strongly associated with heavy bleeding, as they can interfere with normal uterine contraction during menstruation.
Fibroids may also cause pelvic pressure, frequent urination, and bloating. Read our detailed guide on uterine fibroid symptoms, types and treatment for a fuller overview.
Uterine Polyps
Endometrial polyps are overgrowths of the uterine lining (endometrium) that can cause heavy, prolonged, or irregular bleeding. They are most common in women over 40 and in those taking tamoxifen (a medication used in breast cancer treatment). Polyps are typically detected by transvaginal ultrasound or saline infusion sonohysterography and are usually benign, though evaluation is important to exclude premalignant or malignant lesions 2.
Adenomyosis
Adenomyosis occurs when the endometrial tissue grows into the muscular wall of the uterus (myometrium). This causes the uterus to enlarge and can produce heavy, painful periods. Adenomyosis typically affects women in their 30s–50s and is more common in women who have had children. It is often diagnosed by MRI or ultrasound and can co-exist with fibroids.
Endometrial Hyperplasia and Cancer
Abnormal thickening of the uterine lining (endometrial hyperplasia) can cause heavy bleeding and, in some cases, represents a precancerous condition. Endometrial cancer — the most common gynecologic cancer in the United States — most often presents with abnormal uterine bleeding, particularly in postmenopausal women 1. Any heavy bleeding or bleeding after menopause warrants prompt evaluation to exclude malignancy.
Non-Structural Causes of Heavy Periods
Hormonal Imbalances
The menstrual cycle is regulated by a carefully balanced interplay of estrogen and progesterone. Conditions that disrupt this balance — including polycystic ovary syndrome (PCOS), thyroid disorders, elevated prolactin (hyperprolactinemia), and perimenopause — can produce anovulatory cycles (cycles without ovulation) that cause heavy, irregular, or unpredictable bleeding 3.
In anovulatory cycles, the absence of progesterone after ovulation allows the endometrium to become excessively thick, leading to heavy, sometimes irregular shedding. For a comprehensive look at how hormone disruption drives bleeding changes, see hormonal imbalance symptoms and causes.
Our hormonal imbalance quiz can help you identify which hormonal patterns may be contributing to your symptoms before your appointment.
Bleeding Disorders
Von Willebrand disease — the most common inherited bleeding disorder — is a significant but underrecognized cause of heavy menstrual bleeding, present in approximately 13% of women with menorrhagia 3. Other clotting factor deficiencies and platelet disorders can also present as heavy periods.
A history of easy bruising, prolonged bleeding after surgery or dental procedures, nosebleeds, or a family history of bleeding disorders should prompt evaluation for a coagulopathy.
Medications and IUDs
Several medications can cause or worsen heavy periods, including anticoagulants (blood thinners), aspirin at regular doses, and some non-steroidal anti-inflammatory drugs (NSAIDs) used long-term. Copper intrauterine devices (IUDs) are known to increase menstrual blood loss in many users, particularly in the first few months after insertion. Hormonal IUDs (levonorgestrel), by contrast, typically reduce menstrual bleeding over time.
Complications of Untreated Heavy Periods
The most significant complication of chronic heavy menstrual bleeding is iron-deficiency anemia — which can develop gradually and may cause fatigue, weakness, shortness of breath, difficulty concentrating, and reduced exercise tolerance 1. See our guide on iron deficiency symptoms and treatment for signs to watch for and how a diagnosis is made.
Many women with iron-deficiency anemia from heavy periods attribute their symptoms to stress or busy schedules and do not connect them to their menstrual cycle. Beyond anemia, heavy periods significantly affect quality of life — restricting activities, disrupting sleep, and creating anxiety around social and work situations.
When to See a Doctor
Heavy menstrual bleeding always warrants medical evaluation. See a healthcare provider promptly if: you are soaking a pad or tampon every hour for several hours; you are passing large clots; your bleeding lasts more than 7 days; you have bleeding between periods or after sex; you are experiencing fatigue, breathlessness, or pallor (signs of anemia); your normal activities are restricted by your period; or you have any postmenopausal bleeding.
A gynecologist or primary care physician can conduct a pelvic exam, order blood tests (complete blood count, thyroid function, clotting studies), and arrange imaging such as transvaginal ultrasound. Endometrial biopsy may be recommended for women over 45 or those with risk factors for endometrial cancer.
Frequently asked questions
Is it normal to have very heavy periods?
While some variation in flow is normal, soaking a pad or tampon every hour for multiple consecutive hours, passing clots larger than a quarter, or bleeding for more than 7 days is considered heavy menstrual bleeding and warrants medical evaluation. Heavy periods are not something you should simply endure.
Can stress cause heavy periods?
Stress can affect the hormonal axis that regulates menstruation and may contribute to irregular or heavier cycles in some women. However, stress is rarely the sole cause of significantly heavy bleeding. Other causes — including fibroids, thyroid disorders, and clotting disorders — should be evaluated before attributing heavy periods primarily to stress.
What blood tests are done for heavy periods?
A typical workup includes a complete blood count (to assess for anemia), thyroid function tests, pregnancy test (to rule out pregnancy-related bleeding), and clotting studies including von Willebrand disease screening. Iron studies (ferritin, serum iron, TIBC) are also commonly ordered.
Can heavy periods be a sign of cancer?
Heavy bleeding — particularly in women over 45, in postmenopausal women, or in those with risk factors such as obesity, diabetes, or a history of anovulatory cycles — can be a symptom of endometrial hyperplasia or endometrial cancer. This is one reason why heavy or abnormal bleeding should always be evaluated by a clinician.
What are the treatment options for heavy periods?
Treatment depends on the underlying cause but includes: hormonal options (hormonal IUDs, combined oral contraceptives, progestin therapy, GnRH agonists); non-hormonal medications (tranexamic acid, NSAIDs); surgical procedures (endometrial ablation, myomectomy for fibroids, hysterectomy in refractory cases); and treatment of underlying conditions such as thyroid disease or bleeding disorders.