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Blood clots during your period: What do they mean?

Normally, period fluid is liquid and burgundy or dark red in color, but it’s normal to see blood clots after waking up or sitting still for a long time. This happens when blood starts coagulating. Find out what menstrual clots might be a sign of in this article.

Menstrual discharge consists of endometrial tissue, blood from small blood vessels that are damaged when the uterus sheds its lining, and mucus from the cervical glands.

Blood contains anticoagulants, which are enzymes that keep it from clotting. Thanks to these enzymes, the menstruation is liquid and comes out quickly.

When the uterus sheds its lining, it leaves the body as a natural part of the menstrual cycle. Uterine contractions may play a role in this process. These contractions may also help provide a pressure effect on the blood vessels that supply the endometrium and regulate the rate of menstrual bleeding.

Any process that interferes with the normal functions of the endometrium or with uterine contractions may cause blood clots.

Normal menstrual blood clots are 1 inch (2.5 centimeters) or smaller, and a normal amount of menstrual blood is less than 2.7 fluid ounces (80 milliliters) for the entire period, which shouldn’t interfere with physical, emotional, and social well-being.

If clots appear every month and are bigger than 1 inch, it may indicate a gynecological or bleeding disorder. If you experience this, take note of their color, size, quantity, and consistency and share this information with your health care provider.

If you’re trying to conceive, it’s important to monitor your menstrual flow to see if there are clots.

Clots usually occur during the first days of a heavy period. Otherwise, they may indicate certain gynecological disorders:

  • Polyps or endometrial hyperplasia
  • Uterine fibroids
  • Adenomyosis (abnormal growth and shedding of inner uterine lining inside the uterine walls)

Clotting is sometimes associated with cancer and bleeding disorders.

Clots can signal an issue in the body, and all these conditions can affect the ability to conceive. So if you regularly experience abnormal clots, consult your health care provider.

It’s important to know when period clots should be considered normal or abnormal. 

If the blood clots during your period aren’t larger than a quarter and happen occasionally, that’s normal. Also keep it in mind that period clots are not life-threatening. 

You may notice that your blood clots change in color from red to almost black. This change is also absolutely normal. 

But if you are or suspect you are pregnant and have noticed blood clots, it’s a sign to visit your health care provider as soon as possible to exclude the possibility of miscarriage. 

And if you notice large clots on a regular basis, it’s best to make an appointment with your OB-GYN to check for any complications. 

Normal clots:

  • Are smaller than 1 inch
  • Occur occasionally, usually around the beginning of your period

Abnormal blood clots:

  • Are larger than a quarter
  • Occur frequently

Watch for these other symptoms if you experience heavy flow and menstrual clots:

  • Significant abdominal pain
  • Clots increasing in size
  • Anemia (signs of anemia include shortness of breath, dizziness, faintness, fatigue)

Blood clots are a normal part of our reproductive system. While they might seem alarming, even larger clots aren't cause for concern unless they happen on a regular basis.

If you regularly notice large blood clots, periods with excessive blood loss, or any other worrying symptoms, visit your health care provider for an accurate diagnosis and effective treatment.

“Heavy Menstrual Bleeding.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 20 Dec. 2017, www.cdc.gov/ncbddd/blooddisorders/women/menorrhagia.html.

“Heavy Periods – Overview.” NHS Choices, NHS, www.nhs.uk/conditions/heavy-periods/.

“Menstrual Clots During Heavy Periods: What's Normal & What's Not?” Health Essentials from Cleveland Clinic, 27 Aug. 2020, health.clevelandclinic.org/menstrual-clots-during-heavy-periods-whats-normal-whats-not/.