Blood clots during your period are small, gel-like clumps of blood and tissue that pass from your uterus during menstruation. Most are completely normal, especially during the heaviest days of your cycle. They form when your flow is heavy enough that your body’s natural blood-thinning process can’t keep up.
Why Clots Form During Your Period
Each month, your uterus builds a thick, blood-rich lining in preparation for a possible pregnancy. Estrogen drives this growth during the first half of your cycle, thickening the lining so it could nourish a fertilized egg. After ovulation, progesterone takes over to stabilize and maintain that lining. If pregnancy doesn’t happen, both hormone levels drop, and the lining sheds. That shedding is your period.
As the lining breaks down, your body releases natural anticoagulants to thin the blood and tissue so it can flow out easily. But when blood pools in the uterus or flows faster than those anticoagulants can work, the blood has time to coagulate. The result is a clot, a mixture of blood cells, tissue from the uterine lining, and proteins involved in clotting. This is the same basic process that forms a clot when you cut your finger, just happening inside your uterus instead.
Clots are most common on your heaviest days, typically the first one to three days of your period. They often appear darker in color (deep red, maroon, or almost black) because the blood has had more time sitting in the uterus before passing.
Normal Clots vs. Concerning Clots
Small clots, roughly the size of a dime or a quarter, are normal for many people. You might see a few on your heaviest days and none on lighter days. The color, texture, and exact size can vary from cycle to cycle without meaning anything is wrong.
Clots become a concern when they’re large or frequent. Passing golf ball-sized clots, or passing clots every couple of hours, signals that your bleeding may be heavier than normal. Another red flag: soaking through a pad or tampon in an hour, consistently, for two or more hours in a row. Clinically, heavy menstrual bleeding is defined as losing more than 80 milliliters of blood per cycle, but since nobody measures that at home, the pad-per-hour guideline is a more practical way to gauge it.
What Causes Heavy Clotting
Several conditions can tip the balance toward a thicker uterine lining or heavier flow, both of which increase clotting.
Hormonal imbalances. When estrogen levels run high relative to progesterone, the uterine lining grows thicker than usual. More lining means more material to shed and a heavier flow. This imbalance is common with polycystic ovary syndrome (PCOS), irregular cycles, perimenopause, and obesity. In some cases, prolonged estrogen dominance can lead to endometrial hyperplasia, an overgrowth of the uterine lining that causes particularly heavy, clot-filled periods.
Uterine fibroids. These noncancerous growths in or on the uterus are extremely common and can distort the uterine wall, making it harder for the uterus to contract and stop bleeding efficiently. The result is often prolonged, heavy periods with noticeable clots.
Adenomyosis. This happens when the type of tissue that normally lines the uterus grows into the muscular wall of the uterus itself. It causes the uterus to enlarge and produces heavy, painful periods.
Bleeding disorders. Some people have conditions that affect how well their blood clots throughout the body. Von Willebrand disease is one of the more common ones. If your periods have always been unusually heavy since they started, a blood-clotting disorder is worth investigating.
Thyroid problems. Both an underactive and overactive thyroid can disrupt your menstrual cycle and contribute to heavier bleeding.
When Heavy Periods Cause Anemia
Losing a lot of blood every month can drain your iron stores over time. Red blood cells carry iron, so consistently heavy periods put you at real risk for iron deficiency anemia. This is one of the most common consequences of heavy menstrual bleeding, and it often goes unrecognized because the symptoms creep in gradually.
Signs to watch for include extreme tiredness that doesn’t improve with rest, weakness, pale skin, feeling dizzy or lightheaded, a fast heartbeat, shortness of breath with normal activity, cold hands and feet, and brittle nails. Some people develop unusual cravings for ice, dirt, or other non-food items, a condition called pica that’s a hallmark of significant iron deficiency. If you notice several of these alongside heavy, clot-filled periods, your iron levels are worth checking with a simple blood test.
How Heavy Bleeding Is Evaluated
If your clotting seems excessive, a healthcare provider will typically start with bloodwork to check for iron deficiency anemia, thyroid disorders, and clotting problems. An ultrasound of the uterus can reveal fibroids, polyps, or a thickened lining. In some cases, a small tissue sample from the uterine lining (an endometrial biopsy) is taken to rule out hyperplasia or other abnormalities. These tests are straightforward, usually done in an office visit, and help pinpoint the underlying cause.
Treatment Options That Reduce Clotting
Treatment depends on what’s driving the heavy flow, but several options can reduce both bleeding volume and clot size.
Anti-inflammatory pain relievers. Over-the-counter options like ibuprofen and naproxen do more than ease cramps. They also reduce menstrual blood loss, which can mean fewer and smaller clots. Taking them at the start of your period, rather than waiting until pain peaks, tends to be more effective.
Hormonal treatments. Birth control pills, progesterone supplements, and hormonal IUDs all work by thinning the uterine lining so there’s less tissue to shed each month. A hormonal IUD is one of the most effective options for reducing flow. It delivers a small amount of progestin directly to the uterus, and many people see dramatically lighter periods within a few months.
Tranexamic acid. This prescription medication helps blood clot more effectively throughout the body, which may sound counterintuitive for someone already passing clots. But by reducing the overall volume of menstrual bleeding, it decreases the conditions that cause large clots to form. You only take it during the days you’re actively bleeding.
Procedures. When medication isn’t enough, or when structural issues like fibroids are the cause, procedures ranging from fibroid removal to endometrial ablation (which destroys the uterine lining to reduce or stop bleeding) may be options. These are typically considered after other treatments haven’t provided enough relief.
Practical Ways to Track Your Flow
If you’re unsure whether your clotting is normal, keeping a simple record for two or three cycles can help you and a healthcare provider assess the situation. Note how often you change your pad or tampon, whether you see clots, and roughly how large they are (comparing to a coin is a useful shorthand). Also note your energy levels and any symptoms like dizziness or unusual fatigue, which could point to iron loss. A pattern of large clots, frequent pad changes, or worsening fatigue over several cycles gives a much clearer picture than trying to recall details from memory.