Menstrual clots are lumps of coagulated blood or tissue. They are discharged from the uterus during menstruation when the lining of the uterus or endometrium sheds and is expelled from the uterus through the cervix.
Normally, the body produces anticoagulants or blood thinners to allow the thickened endometrium fragments and blood mixture to pass more freely through the cervix and leave the body. However, sometimes, the body is not able to produce enough thinning agents, causing blood clots to form.
Menstrual clots resemble pieces of mashed-up red fruit. They can be bright red or burgundy and may vary in size. They are usually mixed with liquid blood. The longer the blood stays inside the uterus, the darker it is in color, and the likelier it is to form clots.
Period blood clots
Period blood clots are thick, jelly-like clumps of blood and tissue that are common during menstruation, especially with heavy flow. They form when menstrual blood builds up in the uterus and begins to clot before leaving the body.
Most period blood clots are small (less than the size of a quarter) and dark red in color. These clots are usually normal and part of the body’s natural process of shedding the uterine lining. However, passing large clots frequently or with severe cramping may indicate underlying conditions like fibroids, endometriosis, or a hormonal imbalance.
Causes of menstrual clots
Blood clot formation is the body’s way of controlling bleeding. Blood cells called platelets play an important role in blood clot formation. They release chemicals that start the “clotting cascade.” The fibrin protein is the last step in this cascade, which crosslinks and forms a mesh-like structure that results in a clot.
Platelets can produce these clotting factors. This occurs during menstruation, as well as because of an injury to a blood vessel wall.
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Menstrual clots and heavy periods
The normal menstrual cycle lasts 25 to 32 days. A normal flow lasts between four and seven days and may be accompanied by blood clots. A normal period should normally cause mild to moderate discomfort beginning the first day and then subside.
A period is considered heavy if it soaks through a pad or tampon every hour for several hours or if it lasts for over seven days. Large clots in period blood are also considered signs of heavy periods. Moreover, heavy periods can cause constant pain in the lower abdomen.
Heavy menstrual bleeding can negatively affect a woman’s quality of life and lead to other conditions such as anemia where the body lacks enough healthy red blood cells that can carry oxygen to different organs and tissues in the body. Anemia can make a person feel weak and tired.
Menstrual clots and disease
Blood clots during a period can be normal or a sign of an underlying problem, such as:
- a blockage in the uterus
- fibroids or non-cancerous growths in the wall of the uterus
- hormonal imbalance
- a miscarriage
Menstrual blood clots can also indicate the presence of more serious conditions, such as:
- endometriosis
- adenomyosis
- cancer
Should I worry?
Clots in menstrual blood are considered normal if they are quarter-sized or smaller and only occur occasionally. However, if they frequently occur (more than three times in a row) accompanied by heavy periods and are larger than a quarter, you should seek medical advice.
Menstrual clots and endometriosis
Endometriosis is usually accompanied by heavy bleeding during a woman’s period and chronic pelvic pain. This is because the endometrium-like tissue that has grown outside the uterus reacts to the hormones secreted from the ovaries in the same way as the normal endometrium and starts to bleed.
Treatment
Hormonal medications such as the contraceptive pill can help regulate heavy bleeding and reduce the formation of blood clots. These work by inhibiting the growth of the endometrium. An intrauterine device (IUD) that releases the hormone progestin can also help.
Other treatment options include Cyklokapron and Lysteda. These medications stop blood clots from breaking down and, therefore, may reduce heavy menstruation. Likely, less blood will pool in the uteru,s and menstrual clot formation will diminish.
Laparoscopic surgery often used both to diagnose and treat endometriosis, can also treat heavy bleeding and the formation of blood clots during periods.
Our approach
Endometriosis is associated with heavy periods, prolonged menstrual flow, and large clots. We believe that a transvaginal sonogram, and, if needed, hysteroscopy and endometrial biopsy are necessary for diagnosis. It is also necessary to rule out the diagnoses of myoma, uterine fibroid, polyp, endometrial hyperplasia, and endometrial cancer.
Are blood clots during periods normal?
Yes, small, jelly-like blood clots during periods are common and usually normal, especially on your heaviest days.
Clots form when menstrual blood pools in the uterus or vagina and starts to gel before exiting. You’ll often see them after sitting or sleeping, or when flow is fast. Typical clots look dark red or burgundy, feel soft and gelatinous, and are smaller than 2–3 cm (about grape/quarter size). They often come with stronger cramps because your uterus is working harder to push out thicker blood.
When clots are likely normal
- Heaviest 1–2 days of your period
- After lying down or first thing in the morning
- With regular cycle length and manageable pain
When to call your clinician
- Clots ≥2–3 cm, or you soak a pad/tampon every hour for several hours
- Periods last >7 days, or bleeding suddenly gets much heavier
- You feel dizzy, short of breath, or very tired (possible anemia)
- You have new or worsening pelvic pain, or you’re over 40 with cycle changes
- There’s any chance of pregnancy
What do different sizes and colors of clots mean?
By color:
- Bright red: Fresh, faster flow. Normal early in a period or after standing up.
- Dark red/burgundy: Older blood that pooled and oxidized. Common with “jelly-like” clots.
- Brown: Very old blood leaving slowly; common at the beginning or end of a period.
- Pink or watery: Mixed with cervical fluid; can happen with light flow or spotting.
- Gray tissue or foul odor: Not typical period clots, seek urgent care (possible infection or, if pregnancy is possible, miscarriage tissue).
- Black: Very oxidized blood; can be normal if occasional, but discuss if persistent or with pain.
FAQs
What do large blood clots in the period mean?
Large blood clots during menstruation can often signal an unusually heavy flow, one that simply exceeds your body’s natural ability to keep menstrual blood liquid. When bleeding is rapid, the uterus sheds its lining more quickly than the bloodstream’s anticoagulant proteins can act.
This allows blood to pool and clot into larger masses.
Beyond just a heavier-than-normal period, sizable clots might also point to underlying factors. These could include uterine fibroids, polyps, or adenomyosis, all of which can distort the uterine cavity and impede smooth outflow.
When should I be worried about period blood clots?
You should definitely be concerned about period blood clots if they are consistently larger than a quarter, appear in rapid succession, or coincide with you soaking through a pad or tampon in under an hour. These kinds of patterns strongly suggest unusually heavy menstrual bleeding that might be overwhelming your body’s natural anticoagulant processes.
Why do I have a jelly-like blood clot during my period?
A jelly-like blood clot during your period is usually just pooled menstrual blood that has clotted before leaving the uterus, especially when the flow is heavy or fast.
Period clots form when the endometrium (uterine lining) sheds and mixes with blood and proteins that help it clot. If blood collects in the uterus or vagina before exiting, it can gel and appear dark red or burgundy, soft, and “jelly-like.” You may notice more clots on the heaviest days or after sitting/lying down.
What do endometriosis clots look like?
Endometriosis clots usually look like dark-red or burgundy, jelly-like lumps in period blood. Often larger, thicker, and more frequent during painful, heavy cycles.
People with endometriosis can have heavy menstrual bleeding that leads to more visible period clots. These clots often appear gelatinous, stringy, or liver-like, and may include small, soft tissue fragments mixed with blood.
Important clarity: You can’t see endometriosis lesions in your period blood. Clots reflect how quickly you bleed and how long blood pools before leaving the uterus. They don’t confirm or rule out endometriosis. Diagnosis relies on symptoms, imaging (for endometriomas/deep disease), and sometimes laparoscopy.
What does big blood clots period mean?
Large blood clots during your period are generally considered normal. These clots are mixtures of blood and tissue shed from your uterine lining. Your body typically releases anticoagulants to keep menstrual blood liquid. However, when your flow is heavy, these substances may not work fast enough. This allows blood to pool and form clots before it exits your body.
Clots up to the size of a quarter (about 2.5 cm) are usually not a cause for alarm. If clots are consistently larger than this, it might signal menorrhagia (heavy menstrual bleeding). Uterine fibroids or hormonal imbalances can also cause large clots. It is best to consult a doctor if you are concerned.
What does an unhealthy period clot look like?
An unhealthy period clot is primarily one that is consistently larger than a quarter. This is the main sign you should pay attention to. Passing these large clots frequently is not typical. It often occurs with very heavy menstrual bleeding. This condition is also known as menorrhagia. You might find yourself soaking through a pad or tampon every hour.
While the color is often dark red, look out for grayish tissue. A foul odor with clots can also signal an infection. Regularly passing large clots suggests an underlying issue.
Jelly-like blood clots during period is it normal?
Jelly-like blood clots during your period are usually normal and caused by the body shedding the uterine lining. These clots often appear during heavy menstrual flow when blood pools in the uterus and clots before exiting the body. They can be dark red and vary in size, especially on the heaviest days of the period. While small clots (smaller than a quarter) are generally harmless, frequent large clots or severe pain may signal conditions like fibroids, endometriosis, or hormonal imbalances.
Patient story
“My research led me to locate an excision specialist, Dr. Seckin. I had excision surgery with Dr. Seckin in March 2015. I had advanced endometriosis removed in 18 places, including my appendix, intestines, ovary, and uterus. It turns out that the cyst was the least of my problems! Dr. Seckin was wonderful throughout my experience.” —M. Wilson
Get a Second Opinion
Our endometriosis specialists are dedicated to providing patients with expert care. Whether you have been diagnosed or are looking to find a doctor, they are ready to help.Our office is located on 872 Fifth Avenue New York, NY 10065.
You may call us at (646) 960-3080 or have your case reviewed by clicking here.
Dr. Seckin is an endometriosis specialist and women’s reproductive health advocate. He has been in private practice for over 30 years at Lenox Hill Hospital with a team of highly skilled personnel.
Dr. Seckin specializes in advanced laparoscopic procedures and is recognized for his expertise in complex cases of deep infiltrating endometriosis of the pelvis. He is particularly dedicated to performing fertility-preserving surgeries on cases involving the ovaries.
He has developed patented surgical techniques, most notably the “Aqua Blue Excision” technique for a better visualization of endometriosis lesions. His surgical techniques are based on precision and microsurgery, emphasizing organ and fertility preservation, and adhesion and pain prevention.
Dr. Seckin is considered a pioneer and advocate in the field of endometriosis.