What Blood Clots During Your Period Mean

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For most women, occasional clots in period blood are part and parcel of menstruation. In fact, it's both normal and necessary for blood to clot. Take scabs, for example. A scab is comprised of blood that clots and hardens on a wound—forming a sort of protective bandage.

Menstrual blood clots are generally nothing to be concerned about. That said, it's also possible that another underlying condition is causing abnormal blood clots to appear in your period blood.

To help you identify when to see a doctor, we've created this article as a guide to normal and abnormal menstrual blood clots. Read on to learn what they're made of, how they form in your period blood, and the signs that indicate something else could be wrong.

When to See a Doctor for Blood Clots
Verywell / Emily Roberts

How Menstrual Clots Form

Your menstrual period starts when hormones trigger your body to shed the uterine lining (the endometrium). As the lining sheds, small blood vessels bleed.

While this blood is waiting in your uterus to pass through the cervix and vagina, your body produces anticoagulants to help break the blood and tissue down. This allows your body to pass it more easily.

But sometimes, the blood moves faster than the anticoagulants can be produced, and as a result, clots form. Mixed into the menstrual blood are also tiny bits of tissue from the small vessels in the uterine lining.

Thus, what appears to be a blood clot may actually be a clump of endometrial cells. Or, it can be a mixture of both endometrial cells 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. That's because blood is filling the cavity of your uterus and leaving your body so quickly that it doesn't have time to darken.

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


Depending on your age and medical history, any number of factors could be increasing the volume of your menstrual flow and/or causing abnormally large clots to form, including:

  • Uterine fibroids: These noncancerous growths in your uterus are very common.
  • Endometriosis: In this condition, the endometrial tissue in your uterine lining grows outside your uterus, usually onto your fallopian tubes and ovaries.
  • Adenomyosis: This is a condition in which the endometrial tissue in your uterine lining breaks through and begins to grow in your uterine wall, often making your uterus larger.
  • Hormonal imbalances: Hypothyroidism, polycystic ovary syndrome (PCOS), perimenopause, and menopause can cause irregular shedding of the uterine lining, resulting in clotting and heavy bleeding.
  • Miscarriage: Pregnancy loss can happen very early, sometimes before you even know you're pregnant. Clotting and bleeding are common symptoms.
  • Cesarian scar: Some women may experience abnormal bleeding associated with a cesarian scar defect.
  • Cancer in your uterus or cervix: Potential but less likely sources of blood clots.

If you're pregnant and are passing clots, see your doctor or go to the nearest emergency room. 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 of Underlying Conditions

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

  • How long does your period last?
  • How heavy is your usual flow?
  • Have you noticed changes in your flow over time?
  • 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 may also want to do some tests to figure out what might be causing your blood clots. These tests may include:

  • Blood tests: A blood test can be done to look at your thyroid function and to check for a hormonal imbalance, anemia, or an issue with how your blood clots.
  • Pap test: Cells are taken from your cervix and evaluated to see if any changes might be the cause of heavy bleeding and/or clots.
  • Ultrasound: A painless, external procedure that uses sound waves to monitor blood flow and check for fibroids or endometriosis in your uterus.
  • Endometrial biopsy: In this procedure, tissue samples of your uterine lining are removed and evaluated to look for abnormal cells. You may feel some cramping while the procedure is done.
  • Sonohysterogram: To examine your uterine lining, your doctor will inject fluid into your uterus through a tube that is inserted through your vagina and cervix. As the procedure is performed, you may feel some cramping or pressure.
  • Hysteroscopy: For this procedure, you may have general anesthesia or just local anesthesia to numb your pelvic area. Your doctor will insert a thin scope with a light to examine your uterus in detail. This can help diagnose polyps and fibroids.
  • Computerized Tomography (CT) or Magnetic resonance imaging (MRI): Whereas a MRI uses powerful magnets and radio waves to create a picture of your uterus, a CT is more similar to an X-ray. Both are completely painless procedures.

Blood Clots Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

Doctor Discussion Guide Woman

Treatment for Abnormal Clots

Your treatment will depend on a number of factors, including:

  • What's causing your large blood clots and/or heavy bleeding
  • How severe the clots and bleeding are
  • Whether or not other painful symptoms accompany your period
  • Your age, and where you are in your reproductive journey

What is heavy menstrual bleeding, exactly?

Menorrhagia refers to heavy menstrual bleeding and menstrual bleeding that lasts more than seven days. Your flow is considered heavy when you have to change your pad or tampon after less than two hours, or you are passing blood clots that are the size of a quarter or larger.

Iron Supplements

Prolonged heavy menstrual bleeding is a common cause of anemia in women of reproductive age. In fact, one study found that 63.4% of women who experienced menorrhagia also had anemia.

Anemia can make you feel tired, weak, dizzy, and lightheaded—among other symptoms. To treat the condition, your doctor may prescribe iron tablets or supplements to restore iron levels in your blood.

Iron supplementation will not make your period lighter. However, it can remedy the symptoms of anemia and ensure you are not losing too many healthy red blood cells due to heavy bleeding.


Certain contraceptives may reduce your menstrual blood flow and control irregular bleeding. In particular, doctors often prescribe hormonal IUDs or birth control pills.

Two forms of oral contraceptives are used to control heavy bleeding: combination birth control and progresterone-only birth control. Combination birth control pills containing both estrogen and progesterone can reduce your menstrual blood flow by up to 77%.

A progesterone-only pill or injection like Norethindrone (norethisterone) can decrease menstrual blood flow by more than 80%. Noresthisterone is considered the most commonly used progesterone-only oral contraceptive.

Another option is a hormonal IUD like Mirena, which has been shown to reduce menstrual blood flow by up to 95% after one year of use. That said, you may have irregular bleeding and spotting during the first six months or more.


Taken during your period, Advil or Motrin (ibuprofen) can reduce pain, cramping, and the amount of bleeding you have by up to 49%.

Advil and Motrin both fall under the category of non-steroidal anti-inflammatory drugs (NSAIDs). But not all NSAIDs function the same exact way.

Although aspirin is another NSAID used to treat pain and inflammation, taking it can actually increase your menstrual flow.

Hormonal Therapy

Progesterone, estrogen, or a combination of the two can help reduce bleeding. These hormones can be prescribed as contraceptives or in doses that are not specifically tailored for contraception.

The primary difference between hormonal therapy and hormonal contraceptives is that hormonal therapy preserves fertility. It is therefore the preferred option for women who are trying to conceive but would also like to control their heavy menstrual bleeding.

Antifibrinolytic Medicine

Antifibrinolytic medicines like Lysteda (tranexamic acid) or Amicar (aminocaproic acid) can help reduce bleeding. Lysteda can reduce your menstrual flow by up to 58%.

The specific function of antifibrinolytic medication is to slow fibrinolysis—a term that refers to the process of breaking down blood clots.

Surgical Treatment

Surgical treatment may be an option for you when you need to have polyps or fibroids removed. Your doctor may also recommend surgery if medication isn't helping you or is contraindicated for any reason. Surgeries can include:

  • Operative hysteroscopy: This can be used to remove fibroids or uterine lining or to fix problems in your uterus.
  • Endometrial ablation or resection: These procedures remove all or part of your uterine lining to lessen or stop your periods. They also prevent you from having children.
  • Laparoscopy: This minimally invasive surgery can be used to remove small uterine fibroids and growths with a small surgical incision in your abdomen.
  • 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 and you will not be able to conceive. This option is considered when medications haven't helped and/or you are still a long way from menopause.

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


Blood clotting is your body's way of preventing excessive bleeding. It's normal to have clots in your menstrual blood, especially if your flow is heavy.

It's not normal, however, for your period to be so heavy that bleeding lasts longer than seven days, or you are seeing blood clots that are larger than a quarter in size. This is known as menorrhagia, and it's a reason to see your doctor.

Prolonged or untreated heavy menstrual bleeding can lead to anemia. The condition is common in women who experience menorrhagia; if you are anemic, you may feel fatigued, dizzy, and lightheaded, and your doctor may prescribe iron tablets.

Sometimes a heavy flow is simply that—a heavy flow. Other times, it is a symptom of another underlying condition. It's possible you may have uterine fibroids or a hormonal imbalance. Both conditions are common and they're not life-threatening.

If you are pregnant or may become pregnant, there's also a chance the bleeding is caused by a miscarriage or a life-threatening ectopic pregnancy. And while it is much more rare, it is also possible that the heavy bleeding is caused by cervical or uterine cancer.

You know your body better than anyone else; if something feels off, give your gynecologist or primary physician a call.

A Word From Verywell

Unless you are new to having periods, you are probably used to the changes your body undergoes throughout your monthly cycle. You may have several symptoms of PMS one month and hardly any the next. Just as well, the flow of your period can vary in heaviness, and you may occasionally notice clots in your period blood.

In general, these aren't things to worry about. But if you believe you have menorrhagia, your periods are irregular, or you are concerned about painful cramps or other symptoms, go ahead and schedule a visit with your doctor.

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