Why Are My Periods So Heavy? Common Causes Explained

What counts as heavy menstrual bleeding? Medically, the threshold is blood loss greater than 80 ml per cycle, but few women measure this precisely. More practically, heavy bleeding looks like:

• Soaking through a pad or tampon every hour for several consecutive hours
• Needing to use double protection (pad and tampon simultaneously)
• Passing clots larger than a quarter
• Waking up at night to change protection
• Periods lasting longer than 7 days
• Symptoms of anemia — fatigue, pallor, breathlessness — that you attribute to your period

If your periods significantly disrupt your daily life, that's heavy enough to be worth addressing — regardless of how it compares to someone else's experience.

Common Causes of Heavy Periods

Uterine fibroids

Non-cancerous growths in or on the uterus are one of the most common causes of heavy menstrual bleeding. They're present in a significant proportion of women over 30 — [an ultrasound screening study](https://pubmed.ncbi.nlm.nih.gov/12548202/) estimated cumulative fibroid incidence by age 50 at more than 80% in Black women and nearly 70% in white women. Fibroids themselves are almost always benign — the primary issue is the heavy bleeding (and sometimes pelvic pressure or pain) they cause. Size, number, and location determine symptoms.

Adenomyosis

A condition where endometrial tissue grows into the muscle of the uterine wall. This causes the uterus to become enlarged and the lining to bleed more heavily. Adenomyosis is common in women in their 30s-40s and is often associated with painful, heavy periods.

Polyps

Small benign growths on the lining of the uterus (endometrial polyps) or cervix can cause heavier or irregular bleeding.

Hormonal imbalances

When ovulation is irregular or absent, the hormonal cycle that normally regulates the uterine lining is disrupted. Estrogen builds up the lining, but without progesterone from ovulation, the lining grows thicker than normal and sheds irregularly and heavily. This is common in PCOS, perimenopause, thyroid disorders, and certain hormonal conditions.

Thyroid disorders

Both hypothyroidism and hyperthyroidism can affect menstrual flow. Hypothyroidism in particular is associated with heavier periods.

Bleeding disorders

Von Willebrand disease — a relatively common inherited bleeding disorder — is underdiagnosed in women. Heavy periods since adolescence, along with prolonged bleeding from cuts or after surgery/dental work, can be signs.

IUD (intrauterine device)

The copper IUD commonly causes heavier, crampier periods, particularly in the first few months after insertion. Hormonal IUDs typically do the opposite — reducing or eliminating periods.

Medications

Anticoagulants (blood thinners) increase menstrual flow. NSAIDs taken regularly can also affect bleeding patterns.

Endometrial hyperplasia

An overgrowth of the uterine lining — usually due to excess estrogen without sufficient progesterone — can cause heavy and irregular bleeding. It's important to evaluate because in some cases it can progress; treatment exists.

When to Get Evaluated

Any of the following warrants a physician evaluation:

• Bleeding heavy enough to interfere with daily activities
• Bleeding accompanied by severe pelvic pain
• Periods getting progressively heavier over several cycles
• Signs of iron deficiency anemia (fatigue, pale skin, shortness of breath)
• Irregular periods combined with heavy flow
• New onset of heavy bleeding after a period of normal cycles

What Evaluation Typically Includes

A physician will take a menstrual history and may order:

• Blood tests: complete blood count (to check for anemia), thyroid function, potentially von Willebrand factor
• Pelvic ultrasound to look for fibroids, polyps, or adenomyosis
• In some cases, office hysteroscopy for more detailed uterine evaluation

Treatment options range from hormonal management (hormonal IUDs, combined pills, or progestin therapy) to medication to reduce bleeding acutely (tranexamic acid) to procedural options depending on the underlying cause. [A Cochrane systematic review](https://pubmed.ncbi.nlm.nih.gov/32529637/) found that the levonorgestrel-releasing IUS can reduce menstrual blood loss substantially compared with other medical therapies, and [a Cochrane network meta-analysis of first-line treatments](https://pubmed.ncbi.nlm.nih.gov/35638592/) ranked the LNG-IUS and antifibrinolytics (tranexamic acid) as the most effective options for reducing menstrual blood loss.

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