By BSc (biologist & science teacher).
Last Update: 08/28/2015

Typically, women who experience an excessive bleeding during their periods also present menstrual blood clots. This clotting often causes painful cramps when large clots pass through the cervix.

Causes of menstrual blood clots


A heavier bleeding than usual during your period may drain your body’s anticoagulant ability, therefore causing larger clots.

Endometriosis and IUD

Endometriosis, or uterine fibroid, may lead to an excessive clotting during the menstrual cycle. Sometimes, women using a IUD (intrauterine device or coil) might experience a heavier bleeding with larger clots. Nevertheless, at times there is no explanation for clotting.

Pelvic floor dysfunction

Fibroids, polyps, Pelvic Inflammatory Disease (or disorder) (PID), an increased thickness of the uterine lining or endometrial cancer may occasionally lead to blood clotting. This is the reason why it is recommended to see a doctor in order to dismiss severe problems.

Hormonal and blood factors

Women with hormonal imbalances may have a higher risk of excessive bleeding, which leads to clotting. Other reasons may be: underactive thyroid gland, possible blood disorders or blood-thinning medications.


Often ignored, stress is a very common factor leading to excessive bleeding. Sometimes, blood clots during menstruation are just a way in which your body throws away the uterine tissue. Overall, the aim of the menstrual cycle is getting rid of toxins and waste, which are usually expelled as blood clots.

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Authors and contributors

 Iván Ferrer Durbà
Iván Ferrer Durbà
Biologist & Science Teacher
Bachelor's Degree in Biology by the University of Valencia (UV). Postgraduate Course in Secondary Education and Teaching by the University of Portsmouth. Teacher of Sciences at multiple British schools and high schools. More information about Iván Ferrer Durbà

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One comment

    1. Dorothy Perkins

      Hello! I’m 26 and I pass heavy blood clots during menstruation… My gynecologist told me it’s normal but I would like to know whether it is possible to donate them. I mean, there are people suffering from anemia and here I am wasting large amounts of blood… how ironic, isn’t it?