Menstrual Blood Clots: Causes, Normal vs Abnormal
Menstruation is an important aspect of womanhood. It is a process in which a woman’s body prepares for pregnancy. For most women, the experience of menstruation may be different. Many things make one experience different from another, like having light or heavy blood flow, and how this affects your menstrual cycle.
The driving forces behind the varying characteristics of blood can determine the symptoms you experience during menstruation. You’re not alone if you wonder about blood clotting and whether or not it’s happening as normal. Many factors influence the clotting of blood during menstruation, and any disturbances can alter the typical clotting.[1]
Going forward, we’ll take a closer look at what may cause menstrual clots and when they happen. An understanding of the factors that lead to these clots can give you a better idea of how and why your body reacts via certain symptoms such as thickness of blood. Additionally, we’ll examine what constitutes a normal clot and when abnormal clotting demands attention and management.
Overview
In many cases, blood clotting can be a normal part of menstruation. The clotting may occur due to menstrual discharge throughout a cycle. Other times, there may be more serious, abnormal factors that influence the formation of clots.[2]
If you’ve noticed blood clots as rather unusual, the uterine obstructions may be the cause. If these issues persist, you may consider consulting a professional.
Are Menstrual Blood Clots Normal?
- It might be surprising to see a thick glob of menstrual blood, but passing small blood clots should not be a cause for concern in most cases — small means that the clot is not larger than a quarter.
- Why clots form — the uterine lining thickens to prepare for the implantation of a fertilised egg cell — if implantation does not happen, the uterine lining sheds — blood clots are the body's natural response to bleeding.
- One-third of menstruating people experience flows heavy enough to soak through their menstrual products every hour.
- The key size distinction — the quarter rule — is the most practically useful clinical guidance for readers
When Do Clots Happen?
You may be wondering about the development of jelly-like blood clots during periods, is it normal? The answer is yes, as some clots may form at the beginning of the average cycle within the first five days.
Under typical circumstances, the endometrium, the innermost layer of the uterus, grows over a month’s course and sheds if pregnancy does not occur. Menstrual clots are discharged if the blood flows faster than the anticoagulants that the body generates.[3]
Normal vs Abnormal Menstrual Blood Clots: The Size Guide
| Feature | Normal | Potentially Abnormal |
|---|---|---|
| Size | Smaller than a quarter (25mm) | Larger than a grape — seek medical care |
| When they occur | First 1–2 days when flow is heaviest | Frequently throughout the whole period |
| Colour | Dark red or maroon | Bright red — frequent, large bright red clots |
| Associated symptoms | Mild cramps, manageable flow | Associated with heavy cramps or heavy bleeding |
| Impact on daily life | No significant disruption | Soaking through pads every hour for multiple hours |
| Duration | Resolves within 1–2 days of period | Persists throughout the entire period |
Underlying Causes of Menstrual Clots
1. Uterine obstructions
Uterine obstructions or malformations cause the uterus to expand and result in pressure on the uterine wall. These obstructions can be caused by the growth of fibroids or tumors, as well as abnormalities in tissue like adenomyosis and endometriosis. With these obstructions, the uterus is incapable of contracting, and this causes blood to pool up within the cavities and form clots.[4]
2. Fibroids
Fibroids are one type of obstruction that can cause you to experience abnormal clots during menstruation. Fibroids are uterine tumors, often benign, that are overgrowths of smooth tissue and connective tissue within the wall of the uterus. This influences the passing of heavy blood clots, as well as pain and pressure in the abdomen.[5]
In the presence of fibroids, there is often menorrhagia, which is defined as heavy and prolonged bleeding. Fibroids can grow in different locations within the uterus, and if they develop beneath the uterine lining or within the uterine wall, they may lead to abnormal bleeding. Among common period blood clots causes fibroids are frequently discussed because heavy menstrual flow associated with fibroids can increase the likelihood of passing larger blood clots during menstruation. In this case, there may be clots that can equal or surpass a quarter in size.[6]
In addition to abnormal bleeding and blood clots, bladder dysfunction, and iron deficiency anemia due to increased blood flow may also present. There may also be weight gain around the abdomen, resulting in a protruding stomach, accompanied by lower back pain. Having a history of fibroids can also lead to irregular menstruation and fertility struggles.[7]
3. Endometriosis
Endometriosis occurs when endometrial-like tissues accumulate, and the uterine lining grows on the outside of the uterus. As these cells continue to grow and multiply, there will be a buildup of tissues and blood. This can contribute to a sudden gush of blood during period. In addition to the greater volume of blood, there may be menstrual bleeding that occurs in between periods.[8]
Not only is heavy bleeding a common occurrence, but pain is a hallmark of endometriosis. The growth within the lining interacts with hormones related to the ovaries. As growths continue to build in the abdomen and the pelvis, it can lead to chronic pain and menstrual cramps.[9]
Abnormal blood clots may develop due to the connection between endometriosis and estrogen. The hormone estrogen has a regulatory role in the menstrual cycle and influences the thickening of the uterine lining. One response to the shedding of this thickened endometrium is heavier blood flow and clotting during a period.[10]
4. Adenomyosis
Menstrual blood clots are a typical component of adenomyosis, along with painful cramping and heavy bleeding. This condition is characterized by the expansion of the uterus, which grows larger and thicker. This occurs because the uterine lining grows into the uterine wall.[11]
As a result, the uterus can double or triple its average size, and heavy bleeding occurs for a prolonged period. The increased thickness of the endothelial lining and uterine wall leads to this heavier flow during your period. Greater flow can increase the development of blood clots in your menstrual blood far beyond the clots that are normally seen.[12]
While both adenomyosis and endometriosis can cause uterine obstructions via the growth of endometrial-like tissue, the pathogenesis does differ. As previously discussed regarding endometriosis, the tissue grows outside of the uterus, thus impacting other structures like the fallopian tubes or ovaries. With adenomyosis, the endometrial-like tissue grows in the uterine muscle, which results in heavier blood flow compared to endometriosis.[13]
5. Hormonal imbalance
Clots may also be the result of hormonal imbalances like menopause or stress. When the balance between estrogen and progesterone is distorted, it can cause excessive bleeding. Consequently, clots may form.[14]
Additionally, fluctuations in stress hormones and weight are other possibilities to consider. Imbalanced levels of cortisol and other hormones connected to the hypothalamus-pituitary-adrenal (HPA) axis may have a role in endometriosis-related pain.[15]
Autoimmune disorders such as thyroid hormone imbalance may also play a part, with thyroid autoantibodies possibly being involved in the pathophysiology of endometriosis. When hormones are out of regulation, it may lead to heavy bleeding. It may also cause irregularities that impact your menstrual cycle, such as prolonged menstruation or a skipped period.
6. Heavy Menstrual Flow
The most common cause. Large jelly-like period blood clots often go hand in hand with heavy menstrual bleeding — heavy menstrual bleeding is common, affecting about a third of women who seek treatment for it. When blood flows faster than anticoagulants can prevent clotting, clots form
7. Uterine Fibroids
Benign growths inside the uterus increase bleeding and cause frequent, large clots. One of the most common causes of abnormally heavy periods blood clots — affects approximately 20–80% of women by age 50
8. Polycystic Ovary Syndrome (PCOS)
Irregular cycles caused by PCOS may result in heavier shedding once menstruation begins. Infrequent periods allow the uterine lining to thicken more than usual, resulting in heavier flow and more clots when menstruation does occur
9. Miscarriage
Some medical conditions can cause large blood clots often alongside heavy menstrual bleeding. A miscarriage in early pregnancy can be mistaken for a heavy period with large clots. If there is any possibility of pregnancy, see a doctor immediately.
What Does the Appearance of Menstrual Clots Tell You?
- Small dark clots — most common; normal; typically passed on heavy flow days
- Jelly-like clots — you may have spotted jelly-like blood clots mixed in with your period blood — while this might feel alarming at first, clots are actually natural. The jelly texture reflects the mixture of blood, uterine tissue, and mucus.
- Large clots (larger than a quarter) — if you pass clots larger than a grape, seek medical care.
- Bright red clots — may indicate a faster, heavier flow; worth monitoring
- Grey or tissue-like material — if accompanied by pain and possible pregnancy, may indicate miscarriage; seek urgent medical attention
When Should You See a Doctor About Menstrual Blood Clots?
- Pass clots larger than a quarter repeatedly
- Soak through one or more pads or tampons every hour for two or more consecutive hours
- Experience periods lasting longer than seven days nih
- Experience severe pain alongside heavy clotting
- Notice grey or tissue-like material (possible miscarriage)
- Feel dizzy, faint, or short of breath during your period — signs of significant blood loss
Treatment Options for Heavy Periods With Blood Clots
- Hormonal therapy, progesterone supplementation, and NSAIDs may be used to regulate bleeding.
- NSAIDs — ibuprofen and naproxen reduce menstrual flow and pain; most effective when started 1–2 days before the period begins
- Hormonal contraceptives — the pill, hormonal IUD, or injection; regulate and often reduce flow significantly
- Tranexamic acid — a prescription medication that directly reduces bleeding by inhibiting clot breakdown
- Treating underlying conditions — fibroids endometriosis PCOS or thyroid issues are treated based on severity.
- In severe cases procedures like myomectomy polypectomy or endometrial ablation may be recommended.
- Iron supplementation — for anaemia resulting from heavy blood loss.
Normal vs. Abnormal Clots
A normal menstrual blood clot is roughly the size of a dime and may appear bright red at the onset of a period. Abnormal menstrual clots are often larger, sometimes the size of a quarter, and may appear darker red because the blood flow is heavier. If you are wondering when to worry about period blood clots, it may be important to seek medical advice if clots are larger than a quarter, occur frequently, or if heavy bleeding lasts for seven days or more.[16]
Ways to Manage The Symptoms of Heavy Menstrual Periods
The symptoms of heavy menstrual periods can be managed by hormonal contraceptives and medicinal agents. Iron supplements may be necessary if there is too much blood flow. There are also progesterone injections that can decrease blood flow. Additionally, some commonly used pain relievers like ibuprofen can dampen any chronic pain or cramping and can slow down excessive bleeding.[17]
Aside from utilizing pain relievers and medicinal and hormonal agents, physical activity like yoga and stretching can help relieve discomfort from menstrual blood clots. Adequate consumption of nutrients may help alleviate heavy bleeding and clotting as well. B vitamins help to manage blood clots, as well as vitamin K and vitamin D, which are nutrients involved in the adequate coagulation of blood.[18]
Practical Tips for Managing Heavy Periods With Clots:
- Use high-absorbency products, wear dark clothing and keep spare menstrual supplies nearby.
- Period cups — often more practical than pads/tampons for very heavy flow
- Maintain proper hydration and consume iron-rich foods to help prevent anaemia.
- Track your period — a period tracking app helps identify patterns and changes that are important for medical consultations
- Plan around heavy days — know which days are heaviest and manage activities accordingly
Additionally, if menopause is related to your blood clots, using the Menoquil menopause supplement may be of some help. This may influence the balance of estrogen and other hormones and can also ameliorate weight gain and hot flashes if these symptoms occur.
How are Menstrual Clots Treated?
There are various methods for treating menstrual clots and heavy bleeding. This may be through hormonal medicines that support adequate levels of estrogen and progesterone. Additionally, anti-fibrinolytic agents can prolong the breakdown of clots to reduce bleeding. Operations like a hysterectomy may be a viable solution for removing fibroids or other obstructions.[19]
Can Menstrual Blood Clots Lead to Anaemia?
- Heavy periods with significant clotting is one of the most common causes of iron deficiency anaemia in women of reproductive age
- Signs of anaemia from heavy periods — fatigue, weakness, pale skin, dizziness, shortness of breath
- Symptoms indicating anaemia from heavy periods include fatigue, weakness, and dizziness.
- Iron-rich foods — red meat, lentils, spinach, fortified cereals
FAQs
Does PCOS cause blood clots?
Polycystic ovarian syndrome (PCOS) commonly presents with dysfunction of the ovaries and hyperandrogenism. PCOS can lead to menstrual bleeding that can gush out quickly and is so high in volume that it can create blood clots.[20]
Why are PCOS periods so heavy?
In the presence of PCOS, periods can be heavy because the levels of progesterone are often insufficient. Low progesterone influences heavy menstrual bleeding. Severely painful menstrual cramps often accompany this.
Why is my period blood jelly-like?
Your period blood may be jelly-like because the menstrual discharge is composed of blood and tissue from the lining of the uterus. The clots that look like jelly are clumps made of tissues and clots.
Are blood clots during period normal?
Yes, small blood clots during a period can be normal, especially on heavier flow days. They form when blood and tissue collect faster than the body’s natural anticoagulants can break them down.
What causes blood clots during a period?
Large blood clots may occur due to heavy menstrual flow, hormonal changes, uterine conditions, or other underlying factors affecting bleeding patterns.
How big is too big a period blood clot?
Blood clots larger than a quarter (around 2.5 cm) or frequent large clots may warrant medical attention, especially if accompanied by heavy bleeding.
What does a jelly-like period blood clot mean?
Jelly-like clots usually consist of blood mixed with uterine lining tissue and may occur during heavier periods.
When should I be worried about blood clots during period?
Consult a healthcare professional if clots are large, frequent, associated with severe pain, dizziness, or unusually heavy bleeding.
Can stress cause blood clots during a period?
Stress may influence hormones and menstrual patterns, which can indirectly affect flow and clot formation in some individuals.
Do blood clots during my period mean I have fibroids?
Not necessarily, but frequent large clots can sometimes be associated with conditions like uterine fibroids or other menstrual disorders.
Outlook
After discussing the potential causes of your menstrual blood clots, there may be an effective way to manage them and the accompanying symptoms. Seeking professional help to determine which, if any, of these conditions are the underlying cause would be vital for your health.
Knowing the causes can help you seek proper management, like a nutritious diet paired with healthy lifestyle habits, and you’ll be able to improve your quality of life when dealing with menstrual clots.
References
1] ↑Maria Effrosyni Livanou, Alkis Matsas, Valsami S, Papadimitriou DT, Kontogiannis A, Christopoulos P. Clotting Factor Deficiencies as an Underlying Cause of Abnormal Uterine Bleeding in Women of Reproductive Age: A Literature Review. Life. 2023;13(6):1321-1321. doi:
2] ↑Jain V, Chodankar RR, Maybin JA, Critchley HOD. Uterine bleeding: how understanding endometrial physiology underpins menstrual health. Nature Reviews Endocrinology. 2022;18(5). doi:
3] ↑Thiyagarajan DK, Basit H, Jeanmonod R. Physiology, menstrual cycle. National library of medicine. Published April 24, 2019.
4] ↑Piriyev E, Römer T. Coincidence of uterine malformations and endometriosis: a clinically relevant problem? Archives of Gynecology and Obstetrics. 2020;302(5):1237-1241. doi:
5] ↑Hudgens S, Gauthier M, Hunsche E, et al. Development of the Bleeding and Pelvic Discomfort Scale for Use in Women With Heavy Menstrual Bleeding Associated With Uterine Fibroids. Value in Health. Published online July 2022. doi:
6] ↑Havryliuk Y, Setton R, Carlow JJ, Shaktman BD. Symptomatic Fibroid Management: Systematic Review of the Literature. JSLS: Journal of the Society of Laparoendoscopic Surgeons. 2017;21(3). doi:
7] ↑Donnez J, Carmona F, Maitrot-Mantelet L, Dolmans MM, Chapron C. Uterine disorders and iron deficiency anemia. Fertility and Sterility. 2022;118(4):615-624. doi:
8] ↑Endometriosis: MedlinePlus Medical Encyclopedia. medlineplus.gov.
9] ↑Allaire C, Bedaiwy MA, Yong PJ. Diagnosis and management of endometriosis. CMAJ. 2023;195(10):E363-E371. doi:
10] ↑Delgado BJ, Lopez-Ojeda W. Estrogen. Nih.gov. Published October 3, 2019.
11] ↑Nelsen LM, Lenderking WR, Pokrzywinski R, et al. Experience of Symptoms and Disease Impact in Patients with Adenomyosis. The Patient. 2018;11(3):319-328. doi:
12] ↑Vannuccini S, Petraglia F. Recent advances in understanding and managing adenomyosis. F1000Research. 2019;8:283. doi:
13] ↑Zhai J, Vannuccini S, Petraglia F, Giudice LC. Adenomyosis: Mechanisms and Pathogenesis. Seminars in Reproductive Medicine. Published online October 8, 2020. doi:
14] ↑Booyens RM, Engelbrecht AM, Strauss L, Pretorius E. To clot, or not to clot: The dilemma of hormone treatment options for menopause. Thrombosis Research. 2022;218:99-111. doi:
15] ↑Vannuccini S, Clemenza S, Rossi M, Petraglia F. Hormonal treatments for endometriosis: The endocrine background. Reviews in Endocrine and Metabolic Disorders. 2021;23. doi:
16] ↑Centers for Disease Control and Prevention. Heavy Menstrual Bleeding. Centers for Disease Control and Prevention. Published August 28, 2015.
17] ↑Maybin JA, Critchley HO. Medical Management of Heavy Menstrual Bleeding. Women’s Health. 2016;12(1):27-34. doi:
18] ↑Alesi S, Ee C, Moran LJ, Rao V, Mousa A. Nutritional Supplements and Complementary Therapies in Polycystic Ovary Syndrome. Advances in Nutrition. 2021;13(4). doi:
19] ↑James AH. Heavy menstrual bleeding: work-up and management. Hematology. 2016;2016(1):236-242. doi:
20] ↑Siddiqui S, Mateen S, Ahmad R, Moin S. A brief insight into the etiology, genetics, and immunology of polycystic ovarian syndrome (PCOS). Journal of Assisted Reproduction and Genetics. Published online October 3, 2022. doi:
Christine
Christine is a certified personal trainer and nutritionist with an undergraduate degree from Missouri State University. Her passion is helping others learn how strong and healthy they can become by transforming their daily habits through both training and writing. Christine spends most of her time in the gym and learning how she can influence others through positivity!
