Small blood clots during your period are normal. Clots the size of a dime or quarter are common and usually nothing to worry about. But if you’re regularly passing large clots, especially golf ball-sized or bigger, that’s a sign your menstrual bleeding is heavier than it should be and something may be driving it.
Why Period Clots Form
During your period, your body releases natural blood-thinning substances that keep menstrual blood fluid so it can flow out easily. When bleeding is heavy or fast, those substances can’t keep up. Blood pools in the uterus, sits long enough to thicken, and comes out as a clot. This is the same basic clotting process that happens when you cut your skin, just happening inside the uterus instead.
The color and texture of clots reflect how long the blood sat before being shed. Bright red clots are fresh. Dark red or maroon clots with a jelly-like texture have been sitting longer. Both are made of blood cells, uterine lining tissue, and proteins involved in clotting.
Normal Clots vs. Concerning Clots
Dime- or quarter-sized clots, especially on your heaviest day or two, fall within the normal range. Many people pass a few of these each cycle without any underlying problem. What matters more than a single clot is the pattern: how big, how often, and whether it’s changing over time.
Signs that your clots point to something worth investigating include:
- Clots larger than a quarter appearing regularly
- Soaking through a pad or tampon every hour for several hours in a row
- Needing to double up on pads or change them overnight
- Periods lasting longer than seven days
- Clots that are new for you, or getting noticeably bigger
Common Causes of Large Clots
Hormonal Imbalance
Your uterine lining thickens each month in response to estrogen, then sheds when progesterone drops. If you’re not ovulating regularly, which is common during perimenopause, adolescence, or with conditions like polycystic ovary syndrome, progesterone never rises enough to balance estrogen’s effects. The lining keeps growing thicker than normal, and when it finally sheds, there’s simply more tissue and blood to pass. That excess volume overwhelms your body’s natural blood-thinning capacity, producing large clots.
This overgrowth of the lining is called endometrial hyperplasia. It’s one of the most common reasons for suddenly heavier, clottier periods, particularly in your 40s.
Fibroids
Uterine fibroids are noncancerous growths in or on the uterus. They’re extremely common, affecting up to 80% of women by age 50. Fibroids that grow into the uterine cavity or within the muscular wall can distort the shape of the uterus, increase the surface area of the lining, and interfere with the uterus’s ability to contract and slow bleeding. All of this leads to heavier flow and bigger clots.
Adenomyosis
Adenomyosis happens when tissue that normally lines the uterus grows into the muscular wall itself. This causes the uterus to enlarge, sometimes to double or triple its usual size. The result is painful, heavy periods with significant clotting. Adenomyosis is most common in women in their 30s and 40s, and it often coexists with fibroids.
Bleeding Disorders
About 70% of adolescents with an underlying bleeding disorder report passing clots and bleeding through clothes or sheets. Conditions like von Willebrand disease affect the body’s ability to form stable clots throughout the body, and heavy periods with large clots can be the first sign. This is especially worth considering if heavy, clotty periods started with your very first cycle, or if you bruise easily and bleed a long time from cuts.
Copper IUD
The non-hormonal copper IUD is a well-known cause of heavier periods. Research shows that women with copper IUDs have greater clot-dissolving activity in the uterine lining, which sounds counterintuitive but actually leads to more bleeding. The lining breaks down faster and more heavily, often producing larger clots, especially in the first several months after insertion.
The Risk You Might Not Notice: Anemia
Losing large clots cycle after cycle means losing a significant amount of iron. Over months, this can lead to iron deficiency anemia, and because it develops gradually, many people adjust to feeling worse without realizing why. Symptoms include extreme tiredness, weakness, pale skin, shortness of breath with minimal effort, headaches, dizziness, cold hands and feet, and brittle nails.
One of the more distinctive signs is pica: craving things that aren’t food, like ice, dirt, or even the smell of cleaning products. If you’re chewing through cups of ice daily and also passing large clots, the connection is almost certainly iron loss from heavy periods.
How Heavy Clotting Is Evaluated
If you bring up large clots with your doctor, the workup typically starts with blood tests to check for anemia, thyroid problems, and clotting disorders. From there, an ultrasound is usually the first imaging step, looking for fibroids, polyps, or signs of adenomyosis.
If ultrasound doesn’t give a clear picture, more detailed options include sonohysterography, where fluid is injected into the uterus during an ultrasound to get a better view of the lining, or hysteroscopy, where a thin camera is inserted through the cervix to look directly inside the uterus. An endometrial biopsy, a small tissue sample from the lining, may be taken to rule out abnormal cell changes, particularly for women over 35 or those with risk factors for endometrial hyperplasia.
Treatment Options
Treatment depends entirely on what’s causing the heavy bleeding. For hormonal imbalances, hormonal options like birth control pills or a hormonal IUD can thin the lining and dramatically reduce both flow and clotting. These work by providing the progesterone your body isn’t making on its own.
For non-hormonal relief, one of the most effective options is a medication that helps your body’s natural clotting process work better during your period. In clinical studies, this approach reduced menstrual blood loss by 40 to 65 percent, with results appearing within three cycles. Anti-inflammatory pain relievers can also reduce flow by about 20 to 40 percent while helping with cramps.
When fibroids or adenomyosis are the cause, treatment ranges from medications to manage symptoms up to procedures that remove or shrink the growths. For fibroids specifically, minimally invasive options can target the growths while preserving the uterus. Adenomyosis is harder to treat conservatively, and in severe cases, hysterectomy remains the definitive solution.
If anemia is already present, iron supplementation is an important part of the picture regardless of what other treatment you pursue. Rebuilding iron stores typically takes several months of consistent supplementation, even after the heavy bleeding itself is controlled.