Heavier periods can happen for a wide range of reasons, from hormonal shifts and new medications to structural changes in the uterus. A period is generally considered heavy when you need to change your pad or tampon more often than every two hours, your bleeding lasts longer than seven days, or you’re passing clots larger than a quarter. If your flow has noticeably increased from what’s normal for you, something has changed in your body, and it’s worth understanding what might be driving it.
Hormonal Imbalances
The most common explanation for heavier periods is a shift in your hormone balance, specifically between estrogen and progesterone. During a normal cycle, estrogen thickens the uterine lining in the first half, and progesterone stabilizes it after ovulation. If you don’t ovulate in a given cycle, progesterone never kicks in. Without that counterbalance, estrogen keeps building the lining unchecked. When it finally sheds, there’s simply more tissue to come out, which means more blood and often larger clots.
Skipped ovulation (called anovulation) is surprisingly common. It can happen during periods of high stress, significant weight change, intense exercise, or the transition into perimenopause. Conditions like polycystic ovary syndrome (PCOS) also frequently cause anovulatory cycles, leading to irregular but heavy bleeding when a period does arrive.
Thyroid Problems
An underactive thyroid can quietly disrupt your menstrual cycle in multiple ways. Low thyroid hormone suppresses the signals your brain sends to your ovaries, which can interfere with ovulation and throw off estrogen levels. It can also cause your uterine lining to thicken excessively and change the way your blood clots, both of which contribute to heavier flow. If your periods have gotten heavier and you’re also noticing fatigue, weight gain, or feeling cold all the time, a thyroid issue may be the underlying cause.
Fibroids, Polyps, and Adenomyosis
Structural growths in or on the uterus are another major cause of heavy bleeding. Uterine fibroids are noncancerous muscle growths that can range from the size of a seed to larger than a grapefruit. They distort the uterine wall and increase the surface area of the lining, which means more tissue builds up and sheds each cycle. Fibroids are extremely common, particularly in your 30s and 40s.
Uterine polyps are smaller, finger-like growths that form on the inner lining itself. They’re estrogen-sensitive, meaning they grow in response to estrogen, and they can cause bleeding between periods as well as heavier flow during them.
Adenomyosis is a condition where tissue that normally lines the uterus grows into the muscular wall. This makes the uterus larger and spongier, leading to heavy periods with significant clotting, along with intense cramping. Unlike endometriosis, which causes pain primarily during your period, adenomyosis symptoms often persist throughout the month. It’s most common in women in their 30s and 40s, especially after childbirth.
Your IUD or Medications
If you recently had a copper IUD placed, that’s one of the most straightforward explanations for heavier bleeding. Copper IUDs are well known for increasing menstrual flow and cramping, particularly in the first few months after insertion. Hormonal IUDs typically have the opposite effect, often reducing bleeding significantly or stopping periods altogether.
Certain medications can also increase your flow. Blood thinners are an obvious one, but common over-the-counter pain relievers like aspirin, ibuprofen, and naproxen can contribute to heavier bleeding by affecting how your blood clots. If you started taking any of these regularly around the time your periods changed, that may be the connection.
Bleeding Disorders
This is an underrecognized cause, especially in younger people. A multicenter study of 200 adolescents with heavy periods found that 33% had an underlying bleeding disorder. The most common was low levels of von Willebrand factor, a protein that helps blood clot, found in 16% of participants. Another 11% had von Willebrand disease itself, and about 5% had platelet dysfunction.
If your periods have always been heavy since they started, if you bruise easily, bleed a long time from cuts, or have had excessive bleeding after dental work or surgery, a bleeding disorder is worth investigating. Many people go years without a diagnosis because heavy periods are often dismissed as normal.
Signs Your Bleeding May Be Too Heavy
It can be hard to know where the line is between a heavy period and one that needs medical attention. The CDC considers bleeding heavy if you need a new pad or tampon in less than two hours or you’re passing large clots. The NHS puts the clot threshold at about 2.5 centimeters, roughly the size of a quarter. Other signs include needing to double up on protection (wearing a pad and tampon together), waking up at night specifically to change products, or bleeding for more than seven days.
Soaking through a pad or tampon every hour for more than two consecutive hours is a red flag that warrants prompt medical attention.
When Heavy Periods Lead to Anemia
Losing a lot of blood every month can deplete your iron stores over time, leading to iron deficiency anemia. The symptoms can creep up gradually: extreme tiredness, weakness, pale skin, shortness of breath during normal activities, dizziness, cold hands and feet, and brittle nails. Some people develop unusual cravings for ice, dirt, or non-food items, which is a surprisingly reliable signal of iron deficiency.
If you’ve been dealing with heavy periods and recognize several of these symptoms, a simple blood test checking your hemoglobin and ferritin levels can confirm whether your iron is low. This is one of the most common and most treatable consequences of heavy menstrual bleeding, but it often goes unaddressed because people assume feeling tired during their period is just normal.
What to Expect at the Doctor
If you bring up heavier bleeding, your provider will typically start with a detailed history of your cycles and a pelvic exam. Blood work usually includes a check for anemia, thyroid function, and sometimes clotting factors. For women 45 and older, or younger women with risk factors like obesity or PCOS, an endometrial biopsy (a tissue sample from the uterine lining) is often recommended to rule out abnormal cell growth.
A pelvic ultrasound can identify fibroids, polyps, or signs of adenomyosis. In some cases, a procedure called hysteroscopy, where a small camera is used to look inside the uterus, provides a more detailed view and allows polyps or other growths to be removed at the same time.
Treatment depends entirely on the cause. Hormonal options can thin the lining and reduce flow. If fibroids or polyps are the culprit, removing them often resolves the problem. For bleeding disorders, targeted treatments that support clotting can make a significant difference. The key step is identifying what changed, because heavier bleeding is almost always a symptom of something specific, not a random fluctuation you need to just tolerate.