Blood Clots During Your Period

What They Mean and When to See a Doctor

For most women, the clots that sometimes come out in your period blood are part and parcel of menstruation. In fact, it's both normal and necessary for blood to clot. Clotting is the body's mechanism to stop bleeding. The scab that develops on a cut is in part clotted blood that hardens to create a sort of natural bandage on the wound. While clots in menstrual blood aren't exactly scabs, they're usually nothing to worry about. Here's how normal clots and clumps in your period form, what they're made up of, and how to know when clots may be a sign that something could be wrong.

Normal Clots and Clumps

Your menstrual period starts when hormones trigger your body to start shedding the uterine lining, exposing small blood vessels and causing them to bleed. While this blood is waiting in your uterus to pass through the cervix and vagina during menstruation, your body produces anticoagulants to help break the blood and tissue down so you can pass it more easily. When the blood is moving faster than the anticoagulants can be produced, however, clots can form.

Mixed into menstrual blood are also tiny bits of tissue from the small vessels in the lining of the uterus, the endometrium. Sometimes what appears to be a blood clot is actually a clump of endometrial cells or it can be a mixture of them and blood clots.

Dark red or blackish clots may appear during the first few days of your period when the flow is heaviest. Generally speaking, if the clots are smaller than a quarter and there is not a lot of them, you shouldn't worry.

When your menstrual flow is heavier, blood clots tend to be bigger because there's a larger amount of blood sitting in the uterus. The clots formed are usually a much brighter red color because blood is filling and moving out of the cavity of your uterus more quickly—so quickly it doesn't have time to darken.

This also explains in part why, if you have a heavy flow, you're more likely to have cramping. In order to pass larger blood clots, the cervix has to dilate a bit, causing pain that can be quite intense.

Causes

Depending on your age and your medical history, any number of factors could be pumping up the volume of your menstrual flow and/or causing bigger-than-average clots to form, including:

  • Uterine fibroids, which are noncancerous growths in your uterus and very common.
  • Endometriosis, a condition in which the endometrial tissue in the lining of your uterus grows outside your uterus, usually onto your fallopian tubes and ovaries.
  • Adenomyosis, a condition in which the endometrial tissue in the lining of your uterus breaks through and begins to grow in your uterine wall, often making your uterus larger.
  • Hormonal imbalances, including hypothyroidism, polycystic ovary syndrome (PCOS), perimenopause, and menopause, can cause your menstrual cycles to be irregular, which may result in clotting and heavy bleeding from the uterine lining not being shed regularly. 
  • Miscarriage, which can happen very early, before you even know you're pregnant, and result in clotting and bleeding.
  • Cancer in your uterus or cervix, though this is unlikely.

If you're pregnant and are passing clots, see your doctor or go to the nearest emergency room as this may be a sign of a miscarriage or a potentially life-threatening ectopic pregnancy (in which the fetus has implanted outside of the uterus).

Diagnosis

Blood clots in and of themselves aren't a medical condition or disease but rather a possible symptom of another underlying condition. Your doctor may begin the quest to figure out the cause of your blood clots by asking you some questions such as:

  • When did you first get your period?
  • How long does your period last?
  • How heavy is your flow?
  • Have you noticed changes in your flow over time?
  • How does the bleeding impact your life?
  • Have you been pregnant before?
  • Have you ever had pelvic surgery?
  • Do you use birth control and, if so, what kind?
  • What medications are you on?

Next, your doctor will do a pelvic exam. He or she will likely also want to do some tests to figure out what might be causing your blood clots. These tests may include:

  • Blood test: A blood test can be done to look at your thyroid function and to check for a hormonal imbalance or an issue with how your blood clots. It can also be used to see if you have anemia, a common complication of heavy bleeding that can make you feel tired and weak.
  • Pap test: Cells are taken from your cervix and evaluated for changes to see if this might be the cause of heavy bleeding and/or clots.
  • Ultrasound: Your doctor may do an ultrasound, a painless external procedure that uses sound waves, to monitor blood flow and check for fibroids or endometriosis in your uterus.
  • Endometrial biopsy: During an endometrial biopsy, tissue samples of your uterine lining are removed and evaluated to look for abnormal cells. You may feel some cramping during this procedure.
  • Sonohysterogram: This test lets your doctor look at the lining of your uterus. After fluid is injected into your uterus through a tube that's inserted through your vagina and cervix, an ultrasound is performed. The fluid helps your doctor see your endometrium in more detail so problems can be seen more clearly. This procedure may cause some cramping or pressure.
  • Hysteroscopy: For this procedure, you may have general anesthesia or you may just have local anesthesia to numb your pelvic area. Your doctor inserts a thin scope with a light to look around at your uterus in more detail. This can help diagnose polyps and fibroids.
  • Magnetic resonance imaging (MRI): An MRI uses powerful magnets and radio waves to create a picture of your uterus. This is a completely painless procedure.

Treatment

Treatment for abnormal blood clots means that you need to treat whatever may be causing them. Your treatment will depend on a number of factors including what's causing your large blood clots and/or heavy bleeding, how severe it is, your age, your personal desires, and where you are in your reproductive journey. Medications and surgery are the most common types of treatment for the conditions that can cause blood clots or result from heavy bleeding.

Medications your doctor may use include:

  • Iron supplements: If you have anemia, iron supplements will put iron back into your blood.
  • Birth control pills: Hormonal birth control makes your periods more regular and significantly decreases the menstrual blood flow. Combination birth control pills containing both estrogen and progesterone can reduce your menstrual blood flow by up to 50 percent. A progesterone-only pill or injection like Norethindrone (norethisterone) can decrease menstrual blood flow by up to 83 percent.
  • Intrauterine device (IUD): An IUD like Mirena has been shown to reduce menstrual blood flow by up to 96 percent after one year of use, though you may have irregular bleeding like spotting during the first six months or more
  • Advil or Motrin (ibuprofen): Taken during your period, ibuprofen reduces pain, cramping, and the amount of bleeding you have by 49 percent.
  • Hormonal therapy: Progesterone, estrogen, or a combination of the two can help reduce bleeding.
  • Antifibrinolytic medicines If you don't want to use hormonal therapies, another option is to take Lysteda (tranexamic acid) or Amicar (aminocaproic acid) instead, which help reduce bleeding. Lysteda can reduce your menstrual flow by up to 58 percent.

    Surgical treatment may be an option for you when you need to have polyps or fibroids removed or when medication isn't helping. Surgeries can include:

    • Dilation and curettage (D&C): During this procedure, your cervix is dilated and the top layer of your uterine lining is removed. A D&C often needs to be repeated once the lining builds up again.
    • Operative hysteroscopy: This can be used to remove fibroids or uterine lining or to fix problems in your uterus.
    • Endometrial ablation or resection: These similar procedures remove all or part of your uterine lining, which lessens or stops your periods, but also prevents you from having children.
    • Laparoscopy: This minimally invasive surgery involves small incisions in your abdomen and can be used to remove small uterine fibroids and growths. 
    • Myomectomy: If your fibroids are large, you may need a myomectomy, which involves a larger incision in your abdomen.
    • Hysterectomy: In this surgery, your uterus is removed, which means you won't have periods anymore. This may be an option to consider when medications haven't helped and/or you're finished having children and still a long way from menopause when bleeding issues stop.

      When to See a Doctor

      • If your menstrual bleeding is heavy and requires you to change your tampon or pad every couple of hours
      • If the bleeding lasts longer than seven days
      • If blood clots are larger than a quarter
      • If there is an excessive amount of blood clots
      • If you have extreme abdominal pain with nausea or vomiting
      • If you have bleeding or clots while pregnant
      When to See a Doctor About Menstrual Cramps
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      Article Sources
      • Centers for Disease Control and Prevention (CDC). Heavy Menstrual Bleeding. U.S. Department of Health and Human Services. Updated August 28, 2015. https://www.cdc.gov/ncbddd/blooddisorders/women/menorrhagia.html
      • Mellor Y. Heavy Menstrual Bleeding: Diagnosis and Management Options. The Pharmaceutical Journal. June 2018;300(7914). doi:10.1211/PJ.2018.20204948.
      • The American College of Obstetricians and Gynecologists (ACOG). Heavy Menstrual Bleeding. Published June 2016. https://www.acog.org/Patients/FAQs/Heavy-Menstrual-Bleeding