Heavy Periods: What Could Be Causing Them and What to Do Next

What Counts as a "Heavy" Period

A period qualifies as heavy when blood loss exceeds 80 mL per cycle, but that number is nearly impossible to measure at home. Clinicians now favor patient-reported markers: soaking through a pad or tampon every one to two hours, passing clots larger than a quarter, or bleeding that extends beyond seven days. The NICE guideline on heavy menstrual bleeding defines menorrhagia as "excessive menstrual blood loss which interferes with a woman's physical, social, emotional, or material quality of life" [1].

The Pictorial Blood Loss Assessment Chart

The PBAC scoring system assigns points to each pad or tampon based on saturation level. A score above 100 per cycle correlates with blood loss exceeding 80 mL. It is inexpensive, validated in multiple studies, and gives clinicians an objective baseline to track treatment response [2].

Why Self-Assessment Falls Short

Many women normalize heavy bleeding for years because their cycle has "always been that way." A 2017 survey published in the American Journal of Obstetrics and Gynecology found that fewer than 35% of women with objectively confirmed menorrhagia had ever discussed their bleeding volume with a clinician [3]. That delay matters. Chronic heavy periods drain iron stores, cause fatigue, and lower quality of life long before they prompt a medical visit.

Structural Causes: Fibroids, Polyps, and Adenomyosis

The uterus itself is the source in a large share of cases. Structural abnormalities distort the endometrial cavity, increase surface area, or interfere with the myometrium's ability to contract and limit blood flow.

Uterine Fibroids

Fibroids (leiomyomas) are the single most common structural cause of heavy periods. They are benign smooth-muscle tumors of the uterus, and their prevalence rises steeply with age. By age 50, up to 70% of White women and over 80% of Black women will have at least one fibroid [4]. Submucosal fibroids, those that protrude into the uterine cavity, are most strongly associated with menorrhagia because they expand the endometrial surface and disrupt normal hemostatic mechanisms. A systematic review in Human Reproduction Update confirmed that submucosal location, not fibroid size alone, is the primary determinant of bleeding severity [4].

Endometrial Polyps

Polyps are localized overgrowths of the endometrial lining. They occur in 10-40% of women with abnormal uterine bleeding. Most are benign. However, polyps larger than 1.5 cm or those occurring in postmenopausal women carry a modest malignancy risk (3-5%) and warrant removal [5]. Saline infusion sonography or hysteroscopy identifies polyps more reliably than standard transvaginal ultrasound.

Adenomyosis

In adenomyosis, endometrial glands invade the myometrium. The uterus becomes diffusely enlarged, boggy, and tender. Patients typically report progressively worsening heavy periods accompanied by severe dysmenorrhea. MRI is the gold standard for diagnosis, though transvaginal ultrasound by an experienced sonographer achieves 83% sensitivity [6]. Adenomyosis affects an estimated 20-35% of women, and coexists with fibroids in a substantial minority, making clinical differentiation challenging.

Hormonal and Ovulatory Causes

When the uterus appears structurally normal on imaging, the bleeding is often driven by endocrine disruption. This category accounts for roughly 50% of all cases of heavy menstrual bleeding in reproductive-age women.

Anovulatory Bleeding

Without ovulation, no corpus luteum forms, and progesterone levels remain low. Unopposed estrogen stimulates endometrial proliferation without the organized secretory transformation that leads to a predictable bleed. The result is irregular, prolonged, and often heavy withdrawal bleeding. Anovulation is especially common at the extremes of reproductive life: in adolescents within the first two to three years after menarche, and in perimenopausal women over age 40 [7].

Thyroid Dysfunction

Both hypothyroidism and hyperthyroidism alter menstrual flow. Hypothyroidism is the more common culprit for heavy periods. A study of 171 women with menorrhagia found that 22% had subclinical or overt hypothyroidism based on TSH screening [8]. The mechanism involves altered sex hormone-binding globulin (SHBG) levels, disrupted gonadotropin pulsatility, and impaired endometrial hemostasis. A simple TSH test catches this. Treatment with levothyroxine often normalizes menstrual flow within two to three cycles.

Polycystic Ovary Syndrome

PCOS affects 8-13% of reproductive-age women according to the international evidence-based guideline published in 2018 [9]. Chronic anovulation in PCOS leads to irregular bleeding patterns that can include episodes of heavy flow. The endometrium thickens under prolonged estrogen exposure, then sheds unpredictably. Cyclic progestins or combined oral contraceptives are first-line management for both the bleeding and endometrial protection.

Bleeding Disorders and Coagulation Defects

An underrecognized category. Up to 13% of women presenting with heavy periods from menarche have an underlying inherited bleeding disorder, most commonly von Willebrand disease (VWD) [10].

Von Willebrand Disease

VWD is the most prevalent inherited bleeding disorder, affecting approximately 1% of the general population. Type 1 VWD, the mildest form, accounts for 70-80% of cases and often goes undiagnosed until a woman presents with menorrhagia. The American College of Obstetricians and Gynecologists (ACOG) Committee Opinion recommends screening for bleeding disorders in any adolescent with heavy periods from menarche and in any woman with menorrhagia unresponsive to standard treatment [10].

Other Coagulation Defects

Platelet function disorders, factor XI deficiency, and acquired coagulopathies (from anticoagulant medications such as warfarin, rivaroxaban, or apixaban) also cause heavy menstrual bleeding. Carriers of hemophilia A or B may have reduced factor levels sufficient to produce clinical bleeding. A targeted history, asking about easy bruising, prolonged bleeding from cuts, postpartum hemorrhage, or family history of bleeding, identifies most at-risk patients.

The Diagnostic Workup: A Step-by-Step Approach

Evaluation does not require an immediate MRI or referral. Most primary care clinicians can complete the initial workup in one or two visits.

Step 1: History and Physical

Document cycle length, duration of bleeding, number of pads or tampons used, clot size, and impact on daily activities. Ask specifically about bleeding symptoms outside of menses (nosebleeds, gum bleeding, easy bruising). Perform a pelvic exam to assess uterine size and tenderness.

Step 2: Laboratory Testing

Order a complete blood count (CBC) with ferritin to quantify anemia and iron stores. Add TSH to screen for thyroid disease. For adolescents with heavy periods from menarche, or for any patient with a suggestive bleeding history, send a coagulation panel: PT, aPTT, von Willebrand factor antigen, ristocetin cofactor activity, and factor VIII level [10].

Step 3: Imaging

Transvaginal ultrasound is first-line. It identifies fibroids, adenomyosis (with experienced operators), adnexal pathology, and endometrial thickening. If the endometrial stripe is thickened or irregular, saline infusion sonography or office hysteroscopy provides better cavity detail and detects polyps that standard ultrasound misses [11].

Step 4: Endometrial Sampling

The ACOG practice bulletin on abnormal uterine bleeding recommends endometrial biopsy for women over age 45 with abnormal bleeding, or for younger women with risk factors for endometrial hyperplasia (obesity, chronic anovulation, tamoxifen use, family history of endometrial or colon cancer) [12]. The procedure is performed in the office with a Pipelle catheter, takes under a minute, and has a sensitivity above 90% for detecting endometrial cancer.

Treatment Options That Actually Reduce Blood Loss

Treatment depends on the cause, severity, the patient's reproductive plans, and her preferences. The evidence base supports several approaches with measurable reductions in blood loss.

Levonorgestrel-Releasing Intrauterine Device

The 52-mg levonorgestrel IUD (Mirena) is the single most effective medical treatment for heavy menstrual bleeding. A Cochrane review found it reduced menstrual blood loss by 71-96% within 12 months [13]. It also provides reliable contraception. The device works by inducing endometrial atrophy through local progestin release, suppressing the proliferative changes that drive heavy flow. NICE, ACOG, and the European Society of Human Reproduction and Embryology (ESHRE) all list it as first-line [1].

Tranexamic Acid

Tranexamic acid is an antifibrinolytic that stabilizes clots within the endometrial vasculature. Taken only during heavy bleeding days (typically 1,000-1,300 mg three times daily for up to five days), it reduces blood loss by 34-54% [14]. It is non-hormonal, making it suitable for women who cannot or prefer not to use hormonal methods. A randomized trial published in the American Journal of Obstetrics and Gynecology demonstrated a mean 40% reduction in PBAC scores with tranexamic acid versus placebo [14].

Combined Oral Contraceptives and Cyclic Progestins

Combined hormonal contraceptives reduce menstrual blood loss by 40-50% and regulate cycle timing. They are first-line for anovulatory bleeding in women without contraindications. Cyclic progestins (medroxyprogesterone acetate 10 mg for 10-14 days per cycle or norethindrone 5 mg daily) are an alternative for women who cannot take estrogen [15].

NSAIDs

Nonsteroidal anti-inflammatory drugs, particularly mefenamic acid (500 mg three times daily during menses) and naproxen, reduce blood loss by 20-40% through inhibition of endometrial prostaglandin synthesis. They also treat associated dysmenorrhea. Effect size is smaller than the IUD or tranexamic acid, but they are accessible and inexpensive [16].

Surgical Options

When medical management fails or is contraindicated, surgical intervention becomes appropriate. Hysteroscopic myomectomy is the standard for symptomatic submucosal fibroids. Endometrial ablation destroys the uterine lining and reduces or eliminates bleeding, but it is only appropriate for women who have completed childbearing. Hysterectomy provides definitive cure and remains the most common surgery for refractory menorrhagia in women who do not desire future fertility [17].

Iron Deficiency: The Silent Consequence

Chronic heavy periods are the leading cause of iron deficiency anemia in premenopausal women worldwide. A WHO report estimates that iron deficiency affects over 30% of women globally [18]. Even without frank anemia, depleted ferritin stores (below 30 ng/mL) cause fatigue, brain fog, restless legs, and exercise intolerance.

Repletion Strategy

Oral iron (ferrous sulfate 325 mg every other day) is the standard first approach. Alternate-day dosing improves fractional absorption and reduces GI side effects compared to daily dosing, as demonstrated in a study published in The Lancet Haematology [19]. For women with ferritin below 15 ng/mL, hemoglobin below 10 g/dL, or intolerance to oral iron, intravenous iron sucrose or ferric carboxymaltose replenishes stores faster and more reliably. Ferritin should be rechecked eight to twelve weeks after initiating repletion.

When to Escalate: Red Flags That Require Urgent Evaluation

Not all heavy bleeding can wait for an outpatient workup. Seek same-day evaluation for hemodynamic instability (heart rate above 100, systolic blood pressure below 90), hemoglobin below 7 g/dL, or bleeding that soaks more than one pad per hour for more than six consecutive hours. Acute heavy bleeding in a postmenopausal woman warrants urgent endometrial sampling to rule out malignancy. Adolescents presenting with severe menorrhagia at menarche should be screened for platelet disorders and VWD before attributing bleeding to "just being young" [10].

Intermenstrual bleeding, postcoital bleeding, or new-onset heavy periods in a woman over age 45 should trigger endometrial biopsy regardless of ultrasound findings [12].