Blood Clots During a Period


What are period clots or menstrual clots?

Menstrual clots or blood clots during a period are lumps of coagulated blood or tissue that are discharged from the uterus during menstruation or period.

During menstruation, the lining of the uterus, or endometrium sheds and is expelled from the uterus through the cervix or the opening of the uterus

Normally, the body produces substances known as anticoagulants [1], or blood thinners to allow the thickened endometrium fragments and blood mixture to pass more freely through the cervix and be expelled. However, sometimes, the body is not able to produce enough thinning agents and this causes blood clots to form.

menstrual clots, period clot, Menstrual clots and endometriosis What does a menstrual clot look like?

Menstrual clots look like pieces of mashed up red fruit. They can be bright red or burgundy in color and may vary in size. They are usually mixed up 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.


Blood clot formation is the body’s way of controlling bleeding [2]. Blood cells called platelets play an important role in blood clot formation. They release chemicals that start the so-called “clotting cascade”. A protein called fibrin is the last step in this cascade, which crosslinks and forms a mesh-like structure that results in a clot [3].

Platelets may be triggered to produce these clotting factors either as a result of an injury to a blood vessel wall, like for example in the case of a grazed knee, or pooled blood, as in the case of heavy menstruation.

Menstrual clots and heavy bleeding

The normal menstrual cycle lasts for 25 to 32 days. The flow is between four and seven days and may be accompanied with blood clots. A normal period should normally cause mild to moderate discomfort starting from 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 more than seven days [4]. Large clots in period blood are also considered to be a sign of heavy periods. 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 [5] where there are not 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.


Blood clots during a period can be normal or a sign of an underlying problem [4] 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 a condition where the lining of the uterus or endometrium grows outside the uterus
  • Adenomyosis, a condition where the lining of the uterus or the endometrium grows into the wall of the uterus
  • Cancer

When should I worry?

Clots in menstrual blood are considered normal if they are small in size (smaller than a quarter) and only occur occasionally. However, if they occur frequently (more then three times in a row) accompanied by heavy periods and are larger than a quarter, medical advice should be sought.

Menstrual clots and endometriosis

Blood clots in periods can be a sign of endometriosis [6], a condition where the endometrium or the lining of the uterus grows outside the uterus. The condition is usually accompanied by heavy bleeding during a woman’s period and chronicle pelvic pain. This is because the endometrium 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 too.


Hormonal medications such as the contraceptive pill can help regulate heavy bleeding and reduce the formation of blood clots [7]. These work by inhibiting the growth of the endometrium. An intrauterine device (IUD) that releases the progestin hormone and that is sometimes used as a method of contraception can also help.

Other treatment options include Cyklokapron [8 and Lysteda [9]. These medicines stop blood clots from breaking down and therefore may reduce heavy menstruation. This way it is hoped that less blood will be pooled in the uterus and menstrual clot formation will be reduced.

Laparoscopic surgery [10] that is often used both to diagnose and treat endometriosis can also be used to treat heavy bleeding and the formation of blood clots in periods.


“Endometriosis is associated with heavy periods, prolonged menstrual flow, and large clots - a transvaginal sonogram and if needed hysteroscopy and endometrial biopsy are necessary for diagnosis. Myoma, uterine fibroid, polyp, endometrial hyperplasia, and endometrial cancer must be the differential diagnosis to be ruled out.” — Dr. Seckin, gynecologist, laparoscopic surgeon, and endometriosis expert.


My research led me to locate an excision specialist, Dr. Seckin. I had excision surgery with Dr. Seckin in March of 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. Read More

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  • Megan Rafael Moreno

    I was in pain for 2 years. I was getting no answers, and because dr Goldstein and dr seckins were willing to see and treat me I'm finally feeling almost back to normal. They were very down to earth and helpful in my time of need. Dr Goldstein was easy to talk to and caring, she took care of me…

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    Dr. Seckin is one of the best endometriosis surgeon. Every time I go to the office, he really listens to me and is always concerned about my issues. Dr Seckin's office staff are a delight and they always work with me. I feel I can leave everything to them and they will take care of it. Thank you to the…

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    Fast forward 5 years to find out incidentally I had a failing kidney. My left kidney was only functioning at 18%. During this time, I was preparing all my documents to send to Dr. Seckin to review. However, with this new information I put everything on hold and went to a urologist. After a few months, no one could figure…

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    I had a wonderful experience working with Dr. Seckin and his team before, during and after my surgery. I came to Dr. Seckin having already had laparoscopic surgery for endometriosis 5 years prior, with a different surgeon. My symptoms and pain had returned, making my life truly challenging and my menstrual cycle unbearable. Dr. Seckin was quick to validate my…

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    I came to Dr. Seckin after years of dealing with endometriosis and doctors who didn't fully understand the disease. He quickly ascertained what needed to be done, laid out the options along with his recommendation and gave me the time to make the right decision for me. My surgery went without a hitch and I'm healing very well. He and…

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    Dr. Seckin brought me back to life! I am now 3 weeks into my recovery after my laparoscopy surgery, and I feel like a new and improved woman! Being diagnosed with Endometriosis, then 25yrs old in 2015, and discovering the severity of my case being stage 4, made me devastated. Dr. Seckin's vast knowledge of the disease, sincere empathy, and…

  • Jason Curry

    My wife had her laparoscopic excision surgery to remove endometriosis with Dr. Seckin on Jan 30, 2014. She doesn't write online reviews so I'm writing this on her behalf. I accompanied her with each office visit she had. The staff--Lucy and Kim, are very friendly, warm and professional. Dr. Seckin was excellent in every capacity. He spent a lot of…

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    He is an awesome doctor who saved my daughters life from debilitating endometriosis..she knew instantly upon awaking from surgery that she was better..that wad May and no complaints only praises for Dr. Wonderful Seckin!!

  • Karen N

    I was diagnosed with Endometriosis at 19. I saw several Endometriosis "Specialists" since then, had a few laproscopic surgeries to "remove" the endometriosis and continued to be in pain. I had a hysterectomy in 2012 and was told this would stop the pain once and for all. No such luck! Tired of spending days in bed with a heating pad,…

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    I researched and found Dr. Seckin after dealing with years of doctors who couldn't help me or refused to go the extra mile for their patients. I have to say I am truly blessed to have found such a compassionate and talented doctor. He is exquisite with everything he does, and both his team at the office and surgical team…

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    Dr. Seckin is a very skilled surgeon. There are not many doctors like him that truly understand the effects of endometriosis. I am lucky to have found him. The staff is wonderful too.

  • Meg Connolly

    Dr. Seckin truly LOVES what he does and cares about his patients from the bottom of his heart. My life has already changed in 3 weeks and I couldn’t be more grateful. Should I ever need another operation for endometriosis, Dr. Seckin will be the one to do it. I recommend him to anyone I come across with similar problems…

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