Small blood clots during your period are completely normal. Clots the size of a dime or even a quarter can be a routine part of menstruation for many people. But clots larger than a quarter, especially if they show up frequently, are a sign of heavy menstrual bleeding that’s worth investigating with a doctor.
Why Periods Produce Clots
During your period, the lining of your uterus breaks down and sheds. Your body releases natural anticoagulants to keep menstrual blood flowing smoothly, but on heavier days, the blood can leave your uterus faster than those anticoagulants can do their job. When that happens, the blood pools and clots before it exits your body. This is why you’re most likely to see clots on your heaviest days, typically the first two or three days of your period.
The clots themselves are a mix of blood cells, tissue from the uterine lining, and proteins that help blood coagulate. Their color ranges from bright red to dark red or even burgundy, and they can feel jelly-like or firm. Seeing a few small ones is simply a sign that your flow was heavy enough to outpace your body’s natural thinning process.
The Size That Matters
The CDC defines heavy menstrual bleeding partly by clot size: clots the size of a quarter (about 2.4 cm across) or larger count as a warning sign. A single quarter-sized clot on your heaviest day isn’t necessarily alarming on its own, but passing golf ball-sized clots, or passing large clots every couple of hours, signals a problem.
Other markers of heavy bleeding include:
- Soaking through a pad or tampon in less than two hours
- Needing to double up on pads
- Waking up at night to change protection
- Periods lasting longer than seven days
If you recognize yourself in several of these, what you’re experiencing has a clinical name: menorrhagia. It affects a significant number of people and is treatable, but it does need evaluation.
What Causes Large Clots
Hormonal Imbalances
Your uterine lining builds up each cycle in response to estrogen, then sheds when progesterone drops. When that balance tips, particularly when estrogen runs high relative to progesterone, the lining grows thicker than usual. A thicker lining means more tissue to shed, heavier bleeding, and bigger clots. One common reason for this imbalance is anovulation, a cycle where your ovaries don’t release an egg. Without ovulation, your body doesn’t produce progesterone the way it normally would, and the lining keeps building.
Fibroids
Uterine fibroids are noncancerous growths in the muscle wall of the uterus. They’re extremely common, and depending on their size and location, they can distort the uterine cavity, increase the surface area of the lining, and interfere with the uterus’s ability to contract and slow bleeding. The result is heavier flow and larger clots.
Polyps
Uterine polyps are soft growths attached to the inner wall of the uterus. They’re estrogen-sensitive, meaning they grow in response to estrogen in your body. Polyps can cause irregular bleeding, very heavy flow, and spotting between periods.
Adenomyosis
In adenomyosis, tissue similar to the uterine lining starts growing into the muscular wall of the uterus itself. This causes the uterus to thicken and enlarge, sometimes to double or triple its usual size. Painful periods with heavy, prolonged bleeding and clotting are hallmark symptoms. Adenomyosis is more common in people who also have endometriosis.
Bleeding Disorders and Medications
Some people have inherited conditions that affect how their blood clots. If you’ve had heavy periods since your very first one, or you also bruise easily, get frequent nosebleeds, or have bled excessively after dental work or surgery, an underlying clotting disorder could be the cause. Blood-thinning medications can also worsen menstrual bleeding by interfering with normal clot formation throughout the body, including the uterus.
The Anemia Connection
Chronically heavy periods drain your iron stores over time. Your body uses iron to make the red blood cells that carry oxygen, so losing too much blood each month can tip you into iron deficiency anemia. This is one of the most common consequences of untreated heavy menstrual bleeding, and it often creeps up gradually enough that you adjust to feeling worse without realizing it.
Signs of iron deficiency anemia include extreme tiredness, weakness, pale skin, dizziness, shortness of breath with mild exertion, cold hands and feet, headaches, and brittle nails. Some people develop unusual cravings for ice, dirt, or other non-food items. If you’re regularly passing large clots and also dealing with persistent fatigue or lightheadedness, low iron is a likely contributor.
How Doctors Figure Out the Cause
The evaluation typically starts with blood work to check for anemia, thyroid disorders, and clotting problems. A pelvic ultrasound is usually the first imaging step, using sound waves to look for fibroids, polyps, or an enlarged uterus. If the ultrasound doesn’t give a clear answer, your doctor may recommend a sonohysterogram, where fluid is injected into the uterus to get a more detailed view of the lining, or a hysteroscopy, where a thin, lighted camera is inserted through the cervix to examine the inside of the uterus directly. A Pap test and sometimes a tissue sample from the uterine lining help rule out precancerous changes.
The specific cause shapes the treatment. Hormonal imbalances often respond to hormonal therapies that regulate the cycle and thin the lining. Fibroids and polyps can sometimes be removed with minimally invasive procedures. Adenomyosis may be managed with hormonal options or, in more severe cases, surgery. Iron supplements address the anemia while the underlying bleeding is brought under control.
Red Flags That Need Urgent Attention
Most heavy periods aren’t emergencies, but some situations call for same-day medical care. Soaking through a pad or tampon every hour for several consecutive hours is one. Feeling faint, dizzy, or confused during your period is another, as these can indicate significant blood loss. A rapid heartbeat or chest pain alongside heavy bleeding also warrants immediate evaluation. These symptoms suggest your body is struggling to compensate for the volume of blood you’re losing, and intervention can prevent the situation from becoming dangerous.