Passing blood clots usually means your body is shedding blood faster than its natural anticoagulants can keep up. In most cases, people searching this phrase are noticing clots during their period, but blood clots can also appear in urine or stool, and each context points to different causes. Small clots are often harmless, while larger or more frequent ones can signal something worth investigating.
Blood Clots During Your Period
Menstrual blood contains a mix of blood, tissue from the uterine lining, and proteins that normally keep the blood in a liquid state as it leaves your body. When your flow is heavy, the blood can pool in the uterus or vagina before it exits, giving it time to clot. The result is those jelly-like clumps that range from dark red to almost black. During lighter days, the body’s natural clot-dissolving proteins handle things fine. On heavier days, they get overwhelmed.
The size of the clots matters more than the clots themselves. Clots smaller than a quarter (about 2.5 cm across) are generally considered normal and don’t need medical attention on their own. Clots the size of a quarter or larger are one of the recognized signs of heavy menstrual bleeding.
Other signs that your period has crossed into “heavy” territory include bleeding that soaks through a pad or tampon every hour for several consecutive hours, needing to double up on pads, having to change protection overnight, or periods lasting longer than seven days. If any of these sound familiar, it’s worth getting evaluated rather than assuming heavy periods are just something you live with.
What Causes Heavy Clotting During Periods
Sometimes heavy clotting is just the way your cycle runs, especially during perimenopause or after starting or stopping hormonal contraception. But persistent large clots often point to a structural or hormonal issue that can be treated.
- Uterine fibroids: Noncancerous growths in the uterine wall that can distort the shape of the uterine cavity and interfere with normal blood outflow. They’re extremely common, affecting up to 80% of women by age 50, and heavy clotting is one of their hallmark symptoms.
- Adenomyosis: A condition where tissue from the uterine lining grows into the muscular wall of the uterus. This makes the uterus enlarged and can cause painful, clot-heavy periods.
- Polyps: Small growths on the inner lining of the uterus that can cause irregular or heavy bleeding.
- Hormonal imbalances: When estrogen and progesterone are out of balance, the uterine lining can build up excessively before shedding, producing a heavier, clottier period.
- Bleeding disorders: Conditions that affect the blood’s ability to clot properly, such as von Willebrand disease, can show up as unusually heavy periods starting from a young age.
Blood Clots During Pregnancy
Passing blood clots during pregnancy is a different situation entirely. Some spotting in early pregnancy is common. The blood can be pink, brown, red, or dark red, and light spotting doesn’t automatically mean something is wrong. But passing actual clots, especially fresh red ones, raises more concern.
In the first trimester, clots can be associated with a subchorionic hematoma (a pocket of blood between the uterine wall and the pregnancy sac) or with miscarriage. The tricky part is that even with an ultrasound, it may not be possible to immediately tell which is happening, depending on the stage of pregnancy and the severity of symptoms. A subchorionic hematoma often resolves on its own, while a miscarriage typically progresses with worsening bleeding and cramping.
The threshold that signals an emergency is filling more than two large pads per hour or passing clots the size of your palm. That level of bleeding during pregnancy warrants immediate evaluation at an emergency department.
Blood Clots in Urine
Finding blood clots when you urinate is less common than menstrual clots and almost always requires investigation. Blood clots in urine can be painful to pass and may cause a blocking sensation if they obstruct urine flow. You might also feel pain in your bladder or lower back.
The most frequent causes include urinary tract infections, kidney or bladder stones, an enlarged prostate, vigorous exercise, or a recent procedure on the urinary tract. In women, endometriosis can also cause blood to appear in urine. Less commonly, blood clots in urine can signal bladder, kidney, or prostate cancer, or a blood-clotting disorder like sickle cell disease or hemophilia.
Any visible blood in your urine, even a single episode, is worth having checked. The color gives a rough clue: bright red or pink blood usually comes from the bladder or urethra, while brownish or tea-colored urine points to the kidneys.
Blood Clots in Stool
Blood in your stool looks different depending on where the bleeding originates, and the color is the most useful signal. Bright red spots or clots on the surface of stool, or on toilet paper, typically come from the rectum or the very end of the large intestine. Hemorrhoids and anal fissures are the most common culprits, and while uncomfortable, they’re rarely dangerous.
Dark red blood mixed into the stool suggests bleeding higher up in the colon or small intestine. This pattern can come from inflammatory bowel disease, diverticular disease, or polyps. Black, tarry, foul-smelling stools point to bleeding even higher, often in the stomach or upper digestive tract. The blood turns dark because stomach acid breaks it down during digestion.
A single episode of bright red blood after straining is common and usually benign. But dark or black stools, blood mixed into the stool rather than sitting on the surface, or any rectal bleeding that recurs over days or weeks warrants a closer look to rule out more serious causes.
How to Track What You’re Seeing
If you’re noticing blood clots in any context, a few details will help you and your healthcare provider figure out what’s going on. Note the color (bright red, dark red, brown, black), the size relative to a familiar object (a dime, a quarter, a golf ball), how often clots appear, and any accompanying symptoms like pain, fatigue, dizziness, or fever. For menstrual clots, tracking over two or three cycles gives a clearer picture than a single period. For clots in urine or stool, even one occurrence is useful information to share.
Fatigue and lightheadedness alongside heavy clotting can indicate anemia from ongoing blood loss. This is especially common with heavy periods that go untreated for months or years. A simple blood test can confirm whether your iron levels have dropped, and treatment is straightforward once the underlying cause of the bleeding is addressed.