Blood Clots During a Period: 7 Causes (& What To Do)

Updated in June 2023

Blood clots during a period can be normal and usually happens due to an imbalance in the woman's hormones that cause the lining of the uterine walls to thicken. This can result in heavier bleeding and the formation of clots ranging from 5 mm to 3-4 cm (around an inch).

However, although having a period with blood clots is normal in most cases and does not require treatment, in other cases it can be a sign of by diseases such as anemia, endometriosis or fibroids, especially if the clots occur with fleshy tissue. 

Therefore it is important to see your doctor to assess the cause of the blood clots during your period and indicate the best treatment. The doctor may order bloodwork to assess your body‘s clotting abilities, as well as an ultrasound to assess your uterine integrity.

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What causes period blood clots?

The most common causes of a blood blots during a period include:

1. Miscarriage

Blood clots during a period may indicate miscarriage in the first trimester of pregnancy, especially if the clot color is slightly yellowish or grayish. It is also common to pass fleshy tissue. Learn more about miscarriage symptoms that can occur in addition to blood blots. 

What to do: to confirm if you have had a miscarriage, it is very important to see your doctor. If the bleeding is very heavy, you should proceed to the hospital immediately to start appropriate treatment and to prevent the loss of too much blood. In most cases, miscarriages occur in the first weeks of pregnancy and bleeding lasts only 2 to 3 days.

2. Endometriosis

Endometriosis is characterized by the growth of endometrial tissue outside the uterus, which can lead to heavy menstruation, intense pain and clot formation. Although this disorder is more frequent in women between the ages of 30 and 40, it can appear at any age. Read more about the endometriosis symptoms that can present and how they vary from woman to woman. 

What to do: you should see your doctor for testing (e.g. a transvaginal ultrasound or blood test) to confirm a diagnosis,. Starting treatment usually depends on the woman's desire to get pregnant and can be done with the use of medication, hormones or surgery.

3. Myoma

Myoma is a benign tumor on the inner wall of the uterus that is also known as a uterine fibroid. It usually causes symptoms such as pain in the uterus, heavy menstruation with the formation of clots or fleshy tissue, and bleeding between periods.

What to do: it is important to see your doctor, who can order a pelvic ultrasound and confirm the presence of the myoma. Treatment can be done with medication, surgery to remove the fibroid or fibroid embolization.

4. Iron deficiency anemia

Iron deficiency anemia may be one of the causes of a period with clots, since iron deficiency can alter blood clotting and lead to menstrual clots. See the main symptoms of anemia to determine your risk for this condition. 

What to do: it is important to see your doctor to request a blood test to confirm anemia. If confirmed, anemia can be treated with an iron supplement, prescribed by the doctor, and by increasing intake of iron-rich foods such as lentils, parsley, beans, and meat. 

Read more about the anemia diet and how to get started. 

5. Other diseases that affect the endometrium

Other endometrial diseases such as endometrial hyperplasia, which is the overgrowth of the endometrium, or endometrial polyps, which is the formation of polyps in the endometrium, can cause you to have a period with clots due to the growth of the uterus.

What to do: you should see your gynecologist to identify the problem promptly. Treatment can be done with the curettage of the endometrial tissue or with the use of progesterone.

6. Vitamin and mineral deficiency

A deficiency in vitamins and minerals that regulate the formation of clots (e.g. vitamin C or K deficiency) can alter the body's ability to clot, and which can result in clots during your period.

What to do: in these cases, it is important to increase your intake of foods like spinach, oranges, strawberries, broccoli or carrots, for example.

7. Gynecological examinations or childbirth

Periods with clots may also occur after gynecological examinations or because of complications during childbirth.

What to do: usually a period can be different for 2 or 3 days, and then resolve and return completely to normal by the next cycle. Therefore, if clots continue to appear, it is important to see your gynecologist.

Fleshy tissue tissue with period

Your period can also come with small pieces of fleshy tissue and this does not mean that the woman has had a miscarriage. These pieces of tissue are little bits of the woman's own endometrium, but they are colorless. Just as the blood has red cells and white cells, the endometrium can also have this coloration.

If your menstruation has pieces of fleshy tissue for 2 consecutive cycles, see your gynecologist for assessment and ask if testing if necessary.