Heavy menstrual bleeding can be more than just an inconvenient period. For some women, bleeding is so heavy or lasts so long that it affects work, sleep, daily activities, and overall quality of life. While a heavier period can happen occasionally, repeated or unusually heavy bleeding may be a sign of an underlying health condition.
Understanding heavy menstrual bleeding causes can help you recognize when your period is outside your normal pattern and when it is time to talk with a healthcare professional.
What Is Heavy Menstrual Bleeding?
Heavy menstrual bleeding, sometimes called menorrhagia, means losing an unusually large amount of blood during a menstrual period or bleeding for longer than is typical.
Every woman’s menstrual cycle is different, so what feels heavy for one person may be normal for another. However, some signs can indicate that menstrual bleeding is unusually heavy.
These may include:
- Needing to change a pad or tampon every hour or two for several hours
- Bleeding that lasts more than seven days
- Passing blood clots that are larger than usual
- Bleeding through clothes or bedding
- Feeling tired, weak, dizzy, or short of breath during or after your period
- Avoiding normal activities because of heavy bleeding
- Needing to wake up during the night to change menstrual protection
Heavy bleeding that repeatedly happens should not simply be accepted as something you have to live with.
Common Causes of Heavy Menstrual Bleeding
There are several possible reasons for unusually heavy periods. Sometimes the cause is related to hormones, while other cases involve changes in the uterus, medications, pregnancy-related conditions, or blood-clotting problems.
1. Hormonal Imbalance
Hormones play an important role in controlling the menstrual cycle. Estrogen and progesterone help regulate the growth and shedding of the uterine lining.
When these hormones are not balanced properly, the uterine lining may become thicker than usual. When it eventually sheds, the bleeding can be heavier or last longer.
Hormonal changes are particularly common during the early teenage years and during the years leading up to menopause. Conditions that affect ovulation can also contribute to irregular or heavy periods.
2. Uterine Fibroids
Fibroids are noncancerous growths that develop in or around the uterus. Some women have fibroids without experiencing any symptoms, while others may have heavy or prolonged menstrual bleeding.
Fibroids can also cause pelvic pressure, painful periods, frequent urination, or lower back discomfort.
The size, number, and location of fibroids can affect the symptoms a woman experiences.
3. Uterine Polyps
Uterine or endometrial polyps are small growths that develop from the lining of the uterus. They can cause irregular bleeding, spotting between periods, or heavier menstrual flow.
Polyps are often benign, but unusual bleeding should still be evaluated by a healthcare professional to determine its cause.
4. Adenomyosis
Adenomyosis occurs when tissue similar to the uterine lining grows into the muscular wall of the uterus.
It can cause heavy periods, painful menstruation, pelvic discomfort, and an enlarged or tender uterus. Some women have mild symptoms, while others experience significant pain and heavy bleeding.
5. Endometriosis
Endometriosis happens when tissue similar to the uterine lining grows outside the uterus. It is often associated with painful periods, but some women may also experience heavy or irregular menstrual bleeding.
Other symptoms can include pelvic pain, pain during sex, pain with bowel movements, and difficulty becoming pregnant.
Not every woman with heavy periods has endometriosis, but it can be one possible cause when heavy bleeding occurs along with significant menstrual pain.
6. Polycystic Ovary Syndrome
Polycystic ovary syndrome, commonly known as PCOS, can affect ovulation and hormone levels.
When ovulation does not happen regularly, the uterine lining may continue to build up. Eventually, this lining can shed irregularly and cause prolonged or heavy bleeding.
Women with PCOS may also experience irregular periods, acne, increased facial or body hair, or difficulty with weight management.
7. Thyroid Problems
The thyroid gland produces hormones that affect many functions throughout the body, including the menstrual cycle.
Both an underactive thyroid and, less commonly, an overactive thyroid can be associated with menstrual changes. An underactive thyroid may contribute to heavier or longer periods in some women.
If heavy bleeding occurs along with unexplained tiredness, changes in weight, feeling unusually cold or hot, or changes in heart rate, a healthcare professional may consider checking thyroid function.
8. Blood-Clotting Disorders
Some women have conditions that make it difficult for their blood to clot normally. These disorders can cause unusually heavy menstrual bleeding, sometimes from the first few periods after puberty.
A woman may also notice frequent nosebleeds, easy bruising, prolonged bleeding after dental procedures, or excessive bleeding after injuries.
If heavy periods have been present since adolescence or there is a family history of unusual bleeding, a doctor may investigate a possible bleeding disorder.
9. Certain Medications
Some medicines can affect menstrual bleeding. Blood-thinning medications, for example, may increase bleeding.
Certain hormonal medications and contraceptive methods can also change menstrual patterns. Depending on the type, some birth-control methods may initially cause irregular or heavier bleeding.
If heavy bleeding started after beginning a medication or contraceptive method, discuss the change with the prescribing healthcare professional rather than stopping the medication on your own.
10. Pregnancy-Related Causes
Bleeding during pregnancy is not a normal menstrual period. Heavy bleeding in someone who could be pregnant can sometimes be associated with miscarriage or other pregnancy-related complications.
For this reason, unexpected heavy bleeding should be taken seriously when pregnancy is possible.
11. Changes in the Uterus
Less commonly, structural changes or certain diseases affecting the uterus can contribute to abnormal bleeding.
Most causes of heavy menstrual bleeding are not cancer. However, particularly in women who are older, have bleeding after menopause, or have other risk factors, a healthcare professional may recommend tests to rule out serious conditions.
Can Heavy Periods Cause Anemia?
Yes. Repeated heavy menstrual bleeding can lead to iron-deficiency anemia because the body loses blood and therefore loses iron.
Anemia may cause:
- Tiredness
- Weakness
- Dizziness
- Headaches
- Pale skin
- Shortness of breath
- Fast heartbeat
- Difficulty concentrating
If y
