Why are There Blood Clots in My Period?

Woman sitting on toilet bowl with hand on chin, mid section
Hitoshi Nishimura/Getty

Question: Is It Normal To Have Blood Clots in My Period?


It depends.

It is understandable why you may be concerned if you see blood clots in your menstrual flow. Usually, this is just a normal part of menstruation and nothing to worry about.

Your menstrual flow is made up of the shedding of the lining of your uterus mixed with the blood that comes from the small vessels that are uncovered when the lining of the uterus is shed.

Sometimes the cells of the shed endometrium clump together and these could appear to be a clot of blood when really it is a clump of tissue or endometrium.

It is very normal for your blood to clot. In fact, that is exactly how your body stops itself from bleeding. And your blood contains certain factors that cause this clotting to happen. So, unless you have an underlying medical problem or you are taking a medication that affects the production or function of your body’s clotting factors or platelets your blood will clot.

The cyclic hormone changes in your body trigger the shedding of the lining of the endometrium. During this process, there is some time when the small blood vessels under the surface are exposed and actively bleed until clotting and other changes in the wall of the uterus stop them from actively bleeding.

During this time blood accumulates in the uterus. And what happens to this blood while it is sitting in the uterus?

It clots.

If your menstrual flow is of average volume it is probable that you may have some actual blood clots. These clots are usually quite small and typically dark red to almost black in color. The clots are small because there is only a moderate amount of blood lost that needs to clot. The clots are dark in color because the blood has been sitting in the uterus for awhile before it comes out in your menstrual flow.

If you are having a heavy menstrual flow your blood clots will appear very different. First of all these clots will be bigger because there is a larger amount of blood sitting in the uterus that needs to clot. Secondly, these clots are usually a much brighter red. This is because the blood is filling the cavity of the uterus faster. So then the pressure of the blood volume is moving it out of the uterus at a faster rate. Because with heavy bleeding the clots tend to be bigger you will likely also have more pain with your menstrual flow because the blood clots need to pass through your cervix. The bigger the blood clot the more the cervix has to dilate or open to let it pass and the more cramping you will have.

Common gynecological conditions that can cause heavy vaginal bleeding that might result in large blood clots include:

  • Uterine fibroids
  • Endometrial polyps
  • Adenomyosis

As always, be sure to discuss any changes in your menstrual bleeding with your healthcare

Updated by Andrea Chisholm MD

Continue Reading