Period Blood Clots: Cause for Concern?

Some are normal, but others can be a sign of issues like uterine fibroids

For most individuals who menstruate, occasional period blood clots are normal and nothing to be concerned about. That said, uterine fibroids, endometriosis, and other conditions can cause blood clots to appear in your period blood too.

One sign of an abnormal blood clot is that it is the size of a quarter or larger. (Normal period blood clots are about the size of a dime.)

This article explains what period blood clots are made of, how they form, and signs that they may not be normal and need to be evaluated by a healthcare practitioner.

Normal Period Blood Clots

Your menstrual period starts when hormones trigger your body to shed the endometrium, or lining of the uterus. As the lining sheds, small blood vessels bleed.

To prevent too much blood from being lost, your body forms blood clots. It does so by using a combination of plasma, or the liquid part of blood, and platelets, or tiny blood cells that bind together to form clots.

Mixed into the menstrual blood are also bits of tissue from the uterine lining. Thus, what appears to be a blood clot may actually be a clump of endometrial cells. It can also be a mixture of both.

The color of period blood clots can vary. Dark red or blackish clots may appear during the first few days of your period when the flow is heaviest. Your period may start or end with bright red blood clots, too. This means the blood is flowing quickly and doesn't have time to darken.

When your menstrual flow is heavier, blood clots tend to be bigger because there's a larger amount of blood sitting in the uterus.

In order to pass large 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.

Abnormal Period Blood Clots

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.

Depending on your age and medical history, there are many conditions that could be increasing the volume of your menstrual flow and/or causing abnormally large clots to form.

Some of these conditions include:

  • Cesarean scar: Some individuals may experience abnormal bleeding associated with the scar from their C-section.
  • Hormonal imbalances: Hypothyroidism, polycystic ovary syndrome (PCOS), perimenopause, and menopause can cause irregular shedding of the uterine lining, resulting in clotting and heavy bleeding.
  • Uterine fibroids: These noncancerous growths in the uterus are common and can cause heavy bleeding.
  • Endometriosis: In this condition, the endometrial tissue in the uterine lining grows outside the uterus, usually onto the fallopian tubes and ovaries.
  • Adenomyosis: This is a condition in which the endometrial tissue in the uterine lining begins to grow into the uterine wall, often making the uterus larger.
  • Miscarriage: Pregnancy loss can happen very early, sometimes before you even know you're pregnant. Clotting and bleeding are common symptoms.
  • Ectopic pregnancy: This is a potentially life-threatening situation in which the fetus has implanted outside of the uterus.
  • Cancer in the uterus or cervix: Potential but less likely causes of blood clots.

When to See a Healthcare Provider

When to See a Doctor for Blood Clots

Verywell / Emily Roberts

See your healthcare provider if you experience any of the following:

  • Blood clots are larger than a quarter
  • An excessive amount of blood clots
  • Menstrual bleeding that is heavy and requires you to change your tampon or pad every couple of hours
  • Bleeding lasts longer than seven days
  • Extreme abdominal pain with nausea or vomiting

Clots During Pregnancy

If you're pregnant and passing blood or clots of any kind, see your healthcare provider or go to the nearest emergency room.

Diagnosis of Underlying Conditions

If you see a healthcare provider about period blood clots, they will begin their evaluation by asking you some questions that can help guide their next steps:

  • How long does your period last?
  • How heavy is your usual flow?
  • Have you noticed changes in your flow over time?
  • What size are the clots?
  • 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?

If the clots seem abnormal or there isn't an obvious cause, they will perform a pelvic exam. They may also want to do some tests to figure out what might be causing your blood clots.

Tests

A healthcare practitioner may order a number of tests as they work to confirm whether your period blood clots are nothing to worry about or if they are a sign of a medical condition.

Tests used as part of the diagnosis process can 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 the cervix and examined to see if any changes might be the cause of heavy bleeding and/or clots.
  • Ultrasound: This painless procedure uses sound waves to monitor blood flow and check for problems like fibroids or endometriosis.
  • Endometrial biopsy: In this procedure, tissue samples of the 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 healthcare provider will inject fluid into the uterus through a tube that is inserted through the vagina and cervix. During the procedure, you may feel some cramping or pressure.
  • Hysteroscopy: Your healthcare provider will insert a thin scope with a light to examine the uterus in detail. This can help diagnose polyps, or abnormal tissue growths, and fibroids.
  • Computerized tomography (CT) or magnetic resonance imaging (MRI): Whereas an MRI uses powerful magnets and radio waves to create a picture of the uterus, a CT is more similar to an X-ray. Both are painless.

Blood Clots Healthcare Provider Discussion Guide

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

Doctor Discussion Guide Woman

Treatment for Abnormal Period Blood Clots

Treatment for abnormal period blood clots may include iron supplements, contraception and other medications, and—in some cases—surgery.

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 plans for reproduction

Iron Supplements

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

Anemia can make you feel tired, weak, dizzy, and lightheaded, among other symptoms. To treat the condition, your healthcare provider 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 help you replace healthy red blood cells.

Contraceptives

Certain contraceptives may reduce your menstrual blood flow and control irregular bleeding. In particular, healthcare providers may suggest hormonal IUDs or birth control pills.

Two forms of oral contraceptives are used to control heavy bleeding: combination birth control and progesterone-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 (also known as norethisterone) can decrease menstrual blood flow by more than 80%. Norethindrone 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.

Ibuprofen

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 can be found in contraceptives, but healthcare practitioners can also prescribe hormones in doses that are not specifically tailored for birth control.

The main difference between those two options? You can still conceive while taking hormonal therapy.

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 healthcare provider may also recommend surgery if medication isn't helping you or is contraindicated for any reason.

Surgical options include:

  • Operative hysteroscopy: This can be used to remove fibroids or the uterine lining, or to fix problems in the uterus.
  • Endometrial ablation or resection: These procedures remove or destroy all or part of the 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, the 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.

Summary

In general, period blood clots aren't something 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 healthcare provider.

Period blood clots, especially if they are large, can be a sign of an underlying condition that requires evaluation and treatment.

A Word From Verywell

Unless you are new to having periods, you are probably used to how your menstruation can vary a bit from month to month.

It can be helpful to track these changes by taking notes in a journal or using a smartphone app. This information can be useful to your healthcare provider if you come to them about period blood clots or other concerns.

Frequently Asked Questions

  • What does a period blood clot look like?

    A menstrual blood clot looks like a dark red blob of blood. Blood clots can vary in size. A normal blood clot is about the size of a dime.

  • Why are my period blood clots stringy?

    Menstrual blood can be thick or stringy on heavy flow days. These jelly-like globs are a mix of blood, tissue, and blood clots released from your uterus. They are normal and typically nothing to be concerned about. 

  • Can stress cause blood clots in period?

    Stress can lead to changes in your period, including heavier bleeding and blood clots.

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Shoupe D. The progestin revolution: Progestins are arising as the dominant players in the tight interlink between contraceptives and bleeding control. Contracept Reprod Med. 2021 Jan;6(3):1-9. doi:10.1186/s40834-020-00142-5

  2. Herman MC, Mol BW, Bongers MY. Diagnosis of heavy menstrual bleeding. Womens Health. 2016 Jan;12(1):15-20. doi:10.2217/whe.15.90

  3. Centers for Disease Control and Prevention. Heavy menstrual bleeding.

  4. Antila RM, Mäenpää JU, Huhtala HS, Tomás EI, Staff SM. Association of cesarean scar defect with abnormal uterine bleeding: The results of a prospective study. Eur J Obstet Gynecol Reprod Biol. 2020 Jan;244(1):134-140. doi:10.1016/j.ejogrb.2019.11.021

  5. Khan AT, Shehmar M, Gupta JK. Uterine fibroids: current perspectives. Int J Womens Health. 2014 Jan;6(1):95-114. doi:10.2147/IJWH.S51083

  6. Kocaoz S, Cirpan R, Degirmencioglu AZ. The prevalence and impacts heavy menstrual bleeding on anemia, fatigue and quality of life in women of reproductive agePak J Med Sci. 2019 Apr;35(2):365-370. doi:10.12669/pjms.35.2.644

  7. Lethaby A, Wise MR, Weterings MA, Bofill Rodriguez M, Brown J. Combined hormonal contraceptives for heavy menstrual bleedingCochrane Database Syst Rev. 2019 Feb;2(2):29. doi:10.1002/14651858.CD000154.pub3

  8. Maybin JA, Critchley H. Medical management of heavy menstrual bleeding. Womens Health. 2016 Jan;12(1):27-34. doi:10.2217/whe.15.100

  9. Dhamangaonkar PC, Anuradha K, Saxena A. Levonorgestrel intrauterine system (Mirena): An emerging tool for conservative treatment of abnormal uterine bleedingJ Midlife Health. 2015 Mar;6(1):26-30. doi:10.4103/0976-7800.153615

  10. Matteson KA, Rahn DD, Wheeler TL 2nd, et al. Nonsurgical management of heavy menstrual bleeding: a systematic reviewObstet Gynecol. 2013 Mar;121(3):632-643. doi:10.1097/AOG.0b013e3182839e0e

  11. James AH. Heavy menstrual bleeding: work-up and management. Hematology Am Soc Hematol Educ Program. 2016 Dec;1(1):236-242. doi:10.1182/asheducation-2016.1.236

  12. The Society of Obstetricians and Gynaecologists of Canada. Hormonal causes of hmb.

By Tracee Cornforth
Tracee Cornforth is a freelance writer who covers menstruation, menstrual disorders, and other women's health issues.