Heavy Menstrual Bleeding: Commonly Missed Diagnoses Every Woman Should Know

Why Heavy Periods Are So Often Misdiagnosed

Heavy menstrual bleeding (HMB) is one of the most mismanaged gynecologic conditions in clinical practice. Around 1 in 5 women of reproductive age experience it at some point, yet studies consistently show that women wait an average of several years before receiving an accurate diagnosis or effective treatment.

Part of the problem is normalization. Women are routinely told that heavy bleeding is "just how periods are," which delays workup for serious and treatable conditions. Another part is that the differential diagnosis for HMB is genuinely wide. The PALM-COEIN classification, adopted by FIGO (the International Federation of Gynecology and Obstetrics), organizes causes into structural abnormalities (Polyp, Adenomyosis, Leiomyoma, Malignancy) and non-structural causes (Coagulopathy, Ovulatory dysfunction, Endometrial, Iatrogenic, Not otherwise classified). Missing a diagnosis in any of these categories means months or years of unnecessary suffering.

What follows is a detailed breakdown of the conditions most commonly missed, with specific guidance on what to ask your clinician and why each matters at different life stages.

Von Willebrand Disease: The Most Overlooked Bleeding Disorder in Women

What it is and why it matters

Von Willebrand disease (VWD) is the most common inherited bleeding disorder in the general population, and women bear a disproportionate burden because the uterine lining is a major site of bleeding challenge. Studies estimate that VWD is present in up to 20% of women presenting with heavy menstrual bleeding, yet it is rarely screened for in primary care.

VWD involves deficient or dysfunctional von Willebrand factor, a protein that helps platelets adhere to damaged vessel walls. Without adequate VWF, bleeding from the shedding endometrium is poorly controlled.

Symptoms that suggest VWD beyond heavy periods

Women with VWD often report:

• Prolonged bleeding after dental procedures or surgery
• Easy bruising, particularly on the arms and legs
• Nosebleeds lasting more than 10 minutes
• Heavy bleeding after childbirth (postpartum hemorrhage)
• A family history of bleeding problems in female relatives

Testing and life-stage considerations

Standard coagulation tests (PT and aPTT) are frequently normal in VWD, which is why a targeted panel, including VWF antigen, VWF ristocetin cofactor activity, and factor VIII, is required. Estrogen raises VWF levels, so testing during the follicular phase, when estrogen is rising but not peak, may give more reliable results. Testing during pregnancy is uninformative because VWF levels rise dramatically in pregnancy regardless of underlying VWD status.

ACOG recommends that all adolescents and women presenting with HMB be evaluated for underlying coagulopathy, including VWD. In practice, this recommendation is widely ignored in primary care settings.

Thyroid Disease: A Systemic Cause Hidden in Plain Sight

Hypothyroidism and the menstrual cycle

Thyroid dysfunction is among the most common systemic causes of HMB, and it is routinely missed because thyroid symptoms develop gradually and clinicians may attribute fatigue, weight change, and heavy periods to separate problems rather than one underlying cause.

Hypothyroidism affects approximately 5% of the U.S. Adult female population, with subclinical hypothyroidism estimated in an additional 5-10%. The mechanism is direct: thyroid hormone regulates factor VIII, von Willebrand factor, and platelet function. Low thyroid hormone impairs all three, resulting in heavier, more prolonged menstrual bleeding.

Hyperthyroidism, conversely, more often causes lighter or absent periods, though some women with Graves disease report unpredictable cycle changes that include occasional heavier episodes.

TSH as a non-negotiable part of the HMB workup

A thyroid-stimulating hormone (TSH) test is inexpensive and highly sensitive. The American Thyroid Association guidelines state that TSH is the single best initial test for thyroid dysfunction. Every woman presenting with HMB should have TSH checked at baseline. Treating confirmed hypothyroidism with levothyroxine frequently reduces or resolves HMB without any additional gynecologic intervention.

If you have been told your heavy periods need surgery or hormonal management before anyone has checked your thyroid, that is worth questioning.

Adenomyosis: The Diagnosis That Took Decades to Get Its Own Name

Adenomyosis occurs when endometrial glands and stroma are found within the myometrium (the muscle wall of the uterus). The result is a uterus that is often enlarged, tender, and prone to heavy, painful periods. For decades, adenomyosis was considered a diagnosis made only at hysterectomy. That has changed.

High-resolution transvaginal ultrasound can now identify adenomyosis with a sensitivity of approximately 72-82% and specificity of 84-85%, and MRI offers even greater accuracy. Despite improved imaging, adenomyosis remains significantly under-diagnosed in women under 40, partly because clinicians historically associated it with older, multiparous women.

Who is at risk and when it appears

Adenomyosis can appear at any reproductive age, including in teenagers and nulliparous women, challenging the outdated "older mother" stereotype. Women with endometriosis have a substantially higher prevalence of co-existing adenomyosis, and these two conditions are managed differently, which makes distinguishing them clinically important.

In perimenopause, adenomyosis often worsens as estrogen levels fluctuate. After menopause, the condition typically regresses, but HMB severe enough to cause anemia before menopause warrants active management rather than watchful waiting.

A practical framework for distinguishing adenomyosis from fibroids in the office: adenomyosis tends to produce diffuse uterine tenderness and a symmetrically enlarged, "boggy" uterus, while fibroids produce irregular, nodular enlargement. Both can coexist. Pelvic ultrasound is the starting point, but a negative scan does not rule out adenomyosis; MRI or specialist review should follow if clinical suspicion remains high.

Endometrial Polyps: Small Structures With Outsized Bleeding Impact

Endometrial polyps are overgrowths of the uterine lining that can cause HMB, intermenstrual bleeding, and postmenopausal bleeding. They are found in up to 32% of women undergoing hysteroscopy for abnormal uterine bleeding, making them one of the most common structural causes of HMB.

Polyps are often missed on standard transvaginal ultrasound, particularly when they are small or the scan is done outside the follicular phase. Saline infusion sonography (SIS), also called sonohysterography, dramatically improves detection and should be requested when polyps are clinically suspected but not seen on standard imaging.

Life-stage note on polyps

In the reproductive years, most endometrial polyps are benign. In postmenopausal women, the risk of malignancy within a polyp rises to approximately 3-4%, with higher risk in women on tamoxifen therapy. Any postmenopausal woman with bleeding, even one episode, deserves endometrial evaluation. This is not a situation where a "wait and see" approach is appropriate.

PCOS and Ovulatory Dysfunction: When the Cycle Itself Is the Problem

Polycystic ovary syndrome (PCOS) is primarily associated with infrequent or absent periods, but it can also cause HMB. The mechanism is anovulation: when ovulation does not occur, progesterone is not produced after the cycle. Without progesterone to stabilize and signal the endometrium to shed, the lining continues to grow under unopposed estrogen stimulation. When it eventually does shed, the bleeding can be extremely heavy and prolonged.

PCOS affects an estimated 8-13% of women of reproductive age worldwide, making it one of the most common endocrine conditions in women. HMB is an underappreciated presentation, particularly in women who do not fit the stereotypical "lean PCOS" or "classic androgenic" picture.

Adolescents and PCOS

In adolescence, irregular and occasionally heavy periods are expected for the first 1-2 years after menarche as the hypothalamic-pituitary-ovarian axis matures. Beyond 2 years, persistent irregularity with HMB warrants PCOS screening. Missing PCOS in a teenager means missing the window to prevent years of endometrial hyperplasia risk.

Uterine Fibroids: Commonly Known but Still Frequently Underestimated

Fibroids (uterine leiomyomata) are the most common benign gynecologic tumors, occurring in up to 80% of Black women and approximately 70% of white women by age 50. Not all fibroids cause symptoms, but submucosal fibroids (those that distort the uterine cavity) are strongly associated with HMB.

The misdiagnosis here is not always about failing to detect fibroids. It is about failing to properly evaluate their type and impact. A fibroid on the outer surface of the uterus (subserosal) rarely causes heavy bleeding, while a small submucosal fibroid can cause profound blood loss. Location, not just size, drives symptoms.

Racial disparities in fibroid diagnosis and treatment

Black women develop fibroids at younger ages, with larger and more numerous tumors, and experience more severe symptoms compared to white women. Research published in the American Journal of Obstetrics and Gynecology found that Black women are significantly more likely to undergo hysterectomy as first-line treatment compared to uterus-sparing procedures, pointing to persistent disparities in care that women should be aware of when reviewing their options.

Perimenopause: When Hormonal Chaos Drives Dangerous Bleeding

Why perimenopause is a high-risk period for HMB

The transition to menopause (perimenopause) typically spans 4-8 years, during which estrogen levels fluctuate erratically and progesterone levels decline as ovulation becomes less frequent. This combination drives anovulatory cycles and unopposed estrogen stimulation of the endometrium, making HMB extremely common in this life stage.

The Study of Women's Health Across the Nation (SWAN) found that heavy or prolonged menstrual bleeding increases significantly in the late reproductive and early perimenopausal years. Despite this, perimenopausal HMB is often minimized by clinicians as an expected inconvenience rather than a symptom requiring investigation.

When perimenopausal bleeding requires endometrial biopsy

Not all perimenopausal HMB is simple hormonal fluctuation. The risk of endometrial hyperplasia and endometrial cancer rises with age, and the same hormonal environment that drives benign perimenopausal HMB also raises cancer risk.

ACOG Practice Bulletin No. 128 recommends endometrial sampling for any woman aged 45 or older with abnormal uterine bleeding, and in younger women with prolonged exposure to unopposed estrogen. If your clinician has not discussed endometrial biopsy and you are 45 or older with HMB, ask directly whether you need one.

Endometrial Hyperplasia and Cancer: The Diagnoses That Cannot Be Missed

Endometrial cancer is the most common gynecologic cancer in the United States. It often presents with abnormal uterine bleeding, including heavy periods, particularly in the perimenopausal and postmenopausal years. The American Cancer Society estimates approximately 67,880 new cases of uterine cancer in 2024.

Endometrial hyperplasia, the precursor lesion, is even more common and is directly driven by prolonged exposure to unopposed estrogen. Risk factors include obesity, PCOS, late menopause, nulliparity, tamoxifen use, and Lynch syndrome.

The critical point: HMB in any postmenopausal woman is not attributable to "heavy periods." There are no normal menstrual periods after menopause. Any vaginal bleeding after the final menstrual period requires prompt evaluation, typically transvaginal ultrasound and endometrial biopsy.

For premenopausal women, the warning signs that should prompt endometrial evaluation regardless of age include:

• Bleeding between periods lasting more than 7 days
• HMB that does not respond to first-line hormonal treatment
• Obesity with irregular cycles
• HMB in a woman with Lynch syndrome or strong family history of uterine or colorectal cancer

Iatrogenic Causes: Medications Your Clinician May Not Connect to Bleeding

Several medications cause or worsen HMB, and the link is not always made in practice.

Anticoagulants. Women taking warfarin, direct oral anticoagulants (DOACs) such as rivaroxaban or apixaban, or even high-dose NSAIDs regularly may experience significantly heavier periods. A systematic review in Blood found that heavy menstrual bleeding affects up to 60-70% of women of reproductive age taking anticoagulants.

Copper IUD. The copper intrauterine device is highly effective contraception but increases menstrual blood loss by an average of 20-50% in the first year of use. Women who switch from hormonal to copper IUD contraception should be counseled to expect heavier periods and monitored for iron-deficiency anemia.

Antipsychotics and dopamine antagonists. These medications raise prolactin levels, disrupt ovulation, and can cause irregular, sometimes heavy cycles. The connection is frequently missed because the prescribing clinician and the gynecologist may not communicate.

The Anemia You Are Living With: Iron Deficiency as a Missed Consequence

Iron-deficiency anemia is both a consequence and a diagnostic clue. Approximately 30% of women with chronic HMB develop iron-deficiency anemia, yet ferritin levels are not routinely checked alongside a full blood count.

Ferritin is the most sensitive early marker of iron depletion. A ferritin level below 30 ng/mL indicates depleted iron stores even when hemoglobin is still within the normal range. Women with ferritin between 30-100 ng/mL and symptoms of fatigue, poor concentration, or hair loss likely have functional iron deficiency.

If you have been told your CBC is "normal" but you are exhausted and losing significant blood each month, request a ferritin level specifically. Normal hemoglobin does not rule out iron deficiency.

Who This Applies to by Life Stage

Adolescents (menarche to age 19)

HMB at menarche is common but not always normal. The top priority is ruling out bleeding disorders, particularly VWD and platelet function defects, which often declare themselves with the first menstrual period. The adolescent who misses school, sports, or social events every month due to her period has a symptom that warrants investigation, not reassurance alone.

Reproductive years (age 20-40)

In this group, fibroids, polyps, adenomyosis, PCOS, thyroid disease, and coagulopathy are the primary diagnostic considerations. Pregnancy must be excluded in any woman of reproductive age presenting with abnormal bleeding.

Perimenopausal (typically age 40-55)

The differential widens significantly. Hormonal anovulation is common but must be a diagnosis of exclusion. Endometrial sampling is often appropriate. Structural causes (fibroids, polyps) remain relevant.

Postmenopausal

Any bleeding is abnormal. Period. Evaluation is mandatory.

How to Advocate for a Complete HMB Workup

Clinician time is limited, and women are conditioned not to complain. These are the specific tests you can ask for by name if they have not been offered:

1. Full blood count with differential
2. Serum ferritin (not just hemoglobin)
3. TSH (thyroid-stimulating hormone)
4. Coagulation screen: PT, aPTT, and ideally VWF panel
5. Transvaginal pelvic ultrasound (standard)
6. Saline infusion sonography if polyps are suspected but not seen
7. Endometrial biopsy if you are 45 or older, or have obesity plus irregular cycles

Keep a period diary for at least two cycles before your appointment. Note the number of pads or tampons used per day, whether you pass clots larger than a quarter, and whether bleeding limits your daily activities. This objective record is more persuasive in a clinical encounter than a qualitative description.

Pregnancy and Bleeding: What Is Never Normal

Heavy bleeding during an established pregnancy is never explained by menorrhagia. If you are pregnant and bleeding heavily, this is a medical emergency. Possible causes include miscarriage, ectopic pregnancy, placenta previa, and placental abruption. Call emergency services or go to an emergency department.

In the postpartum period, continued heavy bleeding beyond 6 weeks after delivery may indicate retained placental tissue, postpartum thyroiditis triggering thyroid dysfunction, or the return of underlying conditions such as fibroids or adenomyosis that were suppressed during pregnancy.

Postpartum thyroiditis deserves special mention: it occurs in approximately 5-10% of women in the year after delivery and can cause both hyperthyroid and hypothyroid phases, the latter of which may present with heavy irregular bleeding as cycles resume.