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    7 Potential Causes for Large Blood Clots During Your Period

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      The presence of blood clots is common during the menstrual cycle, especially during the heaviest days of the period. Most women experience clots at some point in their lives, but heavy bleeding and large clots may be a cause for concern. If you are noticing unusually large blood clots in your flow, schedule an appointment with Dr. Sergei A. Sobolevsky for best advice regarding your condition and if it needs any treatment. The experienced endovascular specialist focuses on the causes behind heavy bleeding and large clots to ensure it is not a serious health issue. He also comes up with the best solutions to prevent excessive loss of blood during your period and helps you continue with routine life even during this time of the month.

      Heavier than usual menstrual bleeding is defined as menorrhagia. If you are changing your pad or tampon every two hours or even sooner and passing blood clots the size of a quarter or larger, you are suffering from heavy periods. It is uncomfortable and often painful and results in debilitating symptoms that can turn serious if you do not seek medical help.

      What Are Blood Clots?

      During menstruation, the lining of the uterus begins shedding due to hormones. Small blood vessels can bleed during this process, and to prevent the body from losing too much blood, plasma and platelets work together to form blood clots.

      According to doctors, blood clots will form anytime you have a certain amount of blood that just sits there, whether it is due to some cut or periods. Period clots happen if you are having a good amount of bleeding. This blood sits inside the uterus, and as it sits there, it forms clots.

      There could be several reasons for a heavier period and abnormal clots during your cycle. It could be the result of some medication you are taking, a change in your lifestyle, or an underlying health condition affecting your cycle. The good news is that many of the conditions, and causes of their symptoms are common and can be treated successfully.

      Blood Clots During Your Period

      Here are seven reasons for large blood clots and heavier-than-normal periods.

      Thyroid Issues

      The thyroid gland present in the neck is responsible for hormone production and distribution. If it is not functioning the right way, it can lead to various complications. Hypothyroidism, or too little production of thyroid hormone, or hyperthyroidism, or production of too much thyroid hormone, can impact the flow and severity of your menstrual cycle.

      It is best to consult your doctor if you experience large blood clots during menstruation, as it could be resulting from thyroid imbalance. The doctor will run a test, called a TSH, thyroid stimulating hormone to measure this hormone. The doctor may also check your levels of T3 and T4 hormone and run anti-thyroid panels to determine if you are suffering from an underlying autoimmune thyroid disease like Hashimoto’s Thyroiditis or Grave’s disease.

      Polyps and Fibroids

      Polyps and fibroids are benign growths that can settle in the uterus and its lining. They make your periods heavy and last longer than usual. There are many types of benign fibroids but submucosal fibroids, or fibroids that grow inside the uterine cavity, are most likely to cause heavy bleeding and large clots. Uterine polyps that grow on the cervix or in the lining of the uterus can also be a reason behind heavy clotting.

      If you continue to experience heavy bleeding and large blood clots during the period, combined with lower back pain or stomach cramps, it could be a uterine obstruction like a fibroid.

      Learn available treatments our top fibroid specialists offer:

      Our top doctors also provide vein treatments in Downtown Brooklyn, NY, including:

      Birth Control

      If you have recently started a new form of birth control, your contraceptive method may be the reason behind large blood clots during periods. Some types of birth control, such as non-hormonal IUDs, can cause heavier-than-normal periods and clots in some women. If you have an IUD and continue to experience heavy clotting and bleeding, it is best to consult a doctor to find out if it is the best form of birth control for you.


      Regular or excessive use of over-the-counter or prescription medications can contribute to heavy periods with large clots. Anti-inflammatory or hormonal medications, like estrogen, progestin, and anticoagulants, can also result in abnormal menstrual flow and bleeding. If you observe big clots of blood in your flow, consult your doctor regarding the medications you are taking for any health conditions and their potential side effects.


      If you have suffered a miscarriage or ectopic pregnancy, it is often mistaken for a heavier period blood clot. In this condition, the fetus begins to form outside of the uterus, usually in one of the fallopian tubes. An ectopic embryo does not survive, and the pregnancy will miscarry, leading to bigger blood clots in periods.


      Endometriosis occurs when the tissues that grow inside the uterus develop outside the uterine cavity. It can lead to heavy clotting and bleeding during the cycle, abdominal pain, and severe cramps. Endometriosis can be very painful, and it is not easy to diagnose it, but it can be managed with medical treatment.

      Polycystic Ovarian Syndrome (PCOS)

      PCOS is another disorder that can cause excessive clotting and bleeding during periods. It is a condition in which follicles grow on the ovaries and prevent eggs from being produced regularly, resulting in irregular menstruation and other problems, including infertility, weight gain, and excessive hair growth.

      Read more: What Does Discharge Look Like Before Your Period?

      Other Conditions That May Cause Blood Clots

      Many other less common chronic conditions can also affect your period and make it heavier than it should be.

      They include:

      • Thyroid diseases
      • Adenomyosis
      • Blood disorders like Von Willebrand disease
      • Pelvic Inflammatory Disease (or PID)
      • Certain types of cancers

      If you are worried about your period turning heavier than normal, fill out a period tracking chart as it happens. It may help your doctor in diagnosing your symptoms accurately.

      Additional symptoms you should watch for include:

      • Abnormally heavy flow
      • Significant abdominal pain and cramping
      • Pain during intercourse
      • Painful urination
      • Frequent clots

      Read more: Is Leg Pain at Night A Warning Sign of Vascular Disease?

      When to See a Doctor for Large Clots During Your Period?

      Blood clots during a period are a normal part of the menstrual cycle. The amount, length, and frequency of menstrual bleeding varies from woman to woman and month to month. However, significant changes to the size and amount of these clots are not common and point to an underlying condition. It is best to consult your doctor if you notice too many large blood clots during your period.

      When speaking to your doctor, you should be prepared with the following information:

      • How long do your periods usually last?
      • How heavy is your usual flow?
      • Do you have any bleeding between periods?
      • Have you noticed any changes over time?
      • Have you experienced pain?
      • Is there any chance you are pregnant?
      • Which medications are you currently taking?
      • Do you have any other medical conditions?

      Your doctor will do a pelvic exam. He may also want to do a blood test to check for anemia, a blood condition that can make you feel weak or tired, a pap test, or pelvic ultrasound to determine the potential underlying problem for large blood clots during your period. If needed, the doctor may recommend medication. In most cases, a hormonal medication to regulate heavy periods is prescribed.

      Visit Downtown Vein & Vascular Center to talk to an expert about your concerns and learn why you are passing large blood clots in your periods and if you need some treatment for them. Dr. Sergei A. Sobolevsky is an experienced endovascular specialist and uses the most state-of-the-art techniques and proven methods to detect your condition accurately. He understands how irritating menorrhagia could be and comes up with the best solutions to prevent heavy blood loss during menstruation and helps you feel better. 

      Dr. Sergei Sobolevsky (Vein & Vascular Specialist)

      Sergei Sobolevsky, MD, is a leading specialist in endovascular medicine with experience in vascular and interventional radiology. Dr. Sobolevsky has decades of experience in the field, with over 25,000 procedures performed, accumulating extensive experience in image-guided minimally invasive medicine, diagnosing and treating a range of conditions.

      Dr. Sobolevsky earned his Doctor of Medicine (MD) degree in 1997 from the University of Colorado School of Medicine. He received his specialty clinical training in vascular and interventional radiology at Harvard University. Later, he earned his MBA from the MIT Sloan School of Management. Recognized as a Castle Connolly Top Doctor and named to the Top Doctors New York Metro Area in 2020, 2021, and 2022, Dr. Sobolevsky is licensed in multiple states, has delivered presentations at numerous institutions in the US and abroad, and now acts as a clinical advisor for the biomedical industry. He also held multiple positions in the field during his career, including Chief of Vascular and Interventional Radiology at the Columbia University Medical Center in New York, NY, Senior Vice President in Clinical and Regulatory Affairs at Artann Laboratories in North Brunswick, NJ, and Medical Director at the American Endovascular and Amputation Prevention Center in Brooklyn.

      More About Dr. Sobolevsky