Why Am I Passing Blood Clots Between Periods?

Approximately every month, a woman’s uterine lining thickens to prepare for pregnancy. If implantation does not occur, the uterus sheds its lining. This shedding is what we call a period or menses.

Most women have a period on a monthly cycle (a commonly referenced frequency is 28 days, though it is not the average frequency for most women is 28 days). The duration of period flow is usually 5-7 days. Every woman’s cycle is different, and some women experience irregular periods, heavier periods, and/or periods with clotting.

Seeing some small clots in your period flow is not necessarily unusual. However, it’s never considered normal to experience heavy bleeding or to pass large quarter-sized clots.

What Is a Period Blood Clot?

The period blood clots that you see during your cycle are different from:

• Normal blood clotting that occurs when you cut yourself 
• Clots that form in deep veins (that can be potentially life-threatening)

Clots that occur during menstrual flow can either be congealed blood that pooled in the back of the vagina while lying or sitting and then all come out at once upon standing OR it can be blood, fluid, or mucous mixed with endometrial tissue.

If you have a heavy flow, there’ll be more blood collecting in the vagina, and this can congeal and form clots.

Clotting: What’s Considered Normal

So, some clotting is considered normal when you’re on your period. According to the CDC, blood clots smaller than a quarter are nothing to be concerned about and don't require medical treatment.

However, the CDC says “blood clots the size of a quarter or larger” should be further investigated. This stands whether they’re showing up as part of your period or not; you'll want to see a doctor for medical advice.

If you’re seeing blood clots when you’re not on your period, you may be bleeding heavily, and this is also something you’ll want a doctor to investigate. 

Keep track of the number of pads or tampons (saturated and not saturated) used when you’re bleeding. Abnormal blood loss can be estimated by tracking pad or tampon use and how quickly they become soaked.

What Could Cause Abnormal Clotting

If you’re passing large clots either during or between periods, it’s something you may need to investigate with your doctor. What follows are some possible causes of abnormal clotting:

Birth Control Cause

• Birth control: According to Medical News Today, bleeding often occurs in the first 6 months of taking a new birth control pill. Doctors sometimes refer to this as breakthrough bleeding. Abnormal uterine bleeding is more likely if you miss a pill, start a new medication, or experience vomiting or diarrhea as the result of illness, according to the Mayo Clinic. 
• Morning-after pill: According to the Mayo Clinic, the morning-after pill may cause breakthrough bleeding or heavy menstrual bleeding. Under normal circumstances, you don't need to consult your doctor. But if bleeding continues for longer than a week, you are saturating a pad or tampon every 1-2 hours, passing clots greater than a quarter-size, you are experiencing signs of symptomatic anemia, or you are experiencing serious abdominal pain, seek medical advice. 
• Intrauterine device (IUD): Some women with an IUD for birth control could also experience non-period bleeding. Side effects of hormonal IUDs include irregular bleeding—which often decreases or stops within 6 months—mood changes, acne, and breast tenderness. The use of copper IUDs can sometimes result in cramps, heavy bleeding, and bleeding between periods. 

External Causes

• Medications: Certain medications may cause abnormal vaginal or uterine bleeding. Your pharmacist should advise you of any serious side effects of the medication.

Common Infections

The following infections may cause vaginal bleeding between periods. It’s worth noting that most infections are treatable. However, an infection may also become more serious if ignored.

• Sexually transmitted infections (STIs), including chlamydia, gonorrhea, and trichomoniasis, may cause abnormal bleeding
• Pelvic inflammatory disease (PID), an ascending infection of the upper  female reproductive system, can cause abnormal or heavy bleeding

Pregnancy-Related Causes

• Ectopic pregnancy: Signs and symptoms of an ectopic pregnancy include abdominal pain and vaginal bleeding
• Miscarriage: Abnormal uterine bleeding is one of the symptoms of miscarriage

Other Causes

• Fibroids or polyps: These benign tumors can cause irregular or heavier periods and vaginal bleeding between periods.
• Endometriosis: According to the Mayo Clinic, women with endometriosis may experience heavier periods or bleeding between periods (intermenstrual bleeding).
• Polycystic ovary syndrome (PCOS): PCOS is a syndrome that is associated with anovulation which can make it difficult to get pregnant. It may also cause irregular uterine bleeding.
• Blood clotting disorders, like von Willebrand disease, may cause heavy menstrual bleeding.
• Other health conditions, like hypothyroidism, liver disease, or chronic kidney disease, can cause heavy menstrual bleeding and clotting.
• Cancer: Cancer or precancer of the cervix, uterus, or (very rarely) fallopian tube may cause abnormal uterine bleeding.

Perimenopause & Menopause

• Perimenopause: The time before menopause is known as perimenopause. During perimenopause, hormones fluctuate greatly. These hormonal shifts can have an effect on ovulation and your entire menstrual cycle. Some women notice irregular or skipped periods and abnormal bleeding between periods during perimenopause. 
• Cancer: According to the Dana-Farber Cancer Institute, spotting in post-menopausal women can, in some cases, be an early sign of cancer and should always be investigated further.

Risks of Heavy Bleeding and Blood Clots Between Periods and Clotting

Depending on the cause of intermenstrual bleeding and blood clots, the risks to your health will be different. However, anemia is one risk that is common to all causes.

Anemia is a condition in which you lack enough healthy red blood cells to carry adequate oxygen to your body's tissues. It can have many causes, including heavy menstrual bleeding or vaginal bleeding between periods (intermenstrual bleeding).

Anemia doesn’t always have symptoms. But, according to the Mayo Clinic, signs and symptoms of anemia include:

• Fatigue
• Weakness
• Pale or yellowish skin
• Irregular heartbeats
• Shortness of breath
• Dizziness or lightheadedness
• Chest pain
• Cold hands and feet
• Headaches

When to Seek Medical Advice for Abnormal Vaginal Bleeding

If you experience heavy vaginal or uterine bleeding or clotting during or outside of your period, it is important to seek medical care and advice.

If heavy bleeding or clotting is accompanied by any of the following symptoms, you'll want to consult your doctor immediately for their advice:

• Heavy periods and/or passing blood clots
• Irregular periods
• Abdominal pain or cramping
• Pain or a burning sensation when peeing
• Abnormal vaginal discharge and/or redness, irritation, and itchiness of the vulva (external genitalia) or vagina.

Even if you don’t have any of the above symptoms, don’t ever ignore abnormal vaginal bleeding or abnormal uterine bleeding in the following situations:

• If you think you’re pregnant: You should always seek medical advice as soon as you think you may be pregnant to be administered a pregnancy test
• When it happens unpredictably or frequently: If spotting seems to happen frequently and randomly, you should definitely look into it
• It begins after unprotected sex: Unprotected sex can put you at risk for STIs and other infections, so if you notice spotting after unprotected sex, it’s wise to see your doctor
• You are on medication that may cause spotting: If spotting can be a side effect of any medication you are on, you should seek out professional help
• Spotting occurs post-menopause: It is never considered normal for anybody post-menopause to experience abnormal vaginal bleeding

How to Prepare for Your Medical Appointment

When you see your doctor, she may need to know the following:

• How long have you been experiencing blood clots between periods been happening: Is it something you’ve always experienced, or did it start recently?
• How often it happens: Is it monthly or irregular? Is this the first time it’s happened?
• If there’s a pattern to the bleeding: Have you observed the bleeding happens on certain days in your menstrual cycle or seemingly at random?
• How long did the bleeding last: 1–2 days or more?
• If you're passing blood clots, are they large blood clots? (coin sizes can be a handy reference)
• How heavy was the blood flow: Did you use any protection? Was a panty liner insufficient?
• Do you usually have a heavy menstrual flow/blood flow? (how many tampons do you use a day, and whether those tampons are super absorbency; do you often saturate your tampons quickly or experience leaks?)
• Was there anything unusual about the blood: Color, texture, or odor?
• Did you also experience pain or other symptoms while you were bleeding?
• Did the bleeding coincide with any increased physical exertion (sex, exercise, etc.)?
• Was there anything you did that seemed to make the spotting worse or better?

Your doctor may also examine you and conduct a pelvic exam. The tests your doctor might recommend will depend on your age and other factors. If you could be pregnant, they will likely obtain a pregnancy test.

They will most likely order bloodwork to check your blood count and see if you’re anemic.

Other tests your doctor may recommend in order to determine a cause of abnormal uterine bleeding may include:

• Endometrial biopsy: An endometrial biopsy is used to screen for abnormal cells in the uterus. Learn more from Johns Hopkins Medicine.
• Hysteroscopy: A hysteroscopy allows your doctor to look inside your uterus in order to diagnose and treat the causes of abnormal bleeding. Learn more from the Cleveland Clinic.
• Pelvic Ultrasound: A pelvic ultrasound allows quick radiographic visualization of the female pelvic organs and structures, including the uterus, cervix, vagina, fallopian tubes, and ovaries. Learn more from Johns Hopkins Medicine.

Possible Treatments for Abnormal Uterine Bleeding or Clotting

The treatment of any unusual vaginal bleeding, blood clots or abnormal uterine bleeding will depend on the cause. Your doctor will first want to diagnose the problem and then they will help you understand your treatment options and determine the right course of action.

Some treatment options for blood clots that your doctor might explore with you may include:

Intrauterine Device (IUD)

It may seem unusual that one possible cause of the bleeding may also be used as a treatment. But hormone-releasing IUDs can help. A hormonal IUD "can decrease menstrual bleeding after three or more months of use," according to the Mayo Clinic. After one year of use, roughly 20% of women stop having periods altogether.

According to the Medical Journal of Australia, one in 20 women will experience abnormal uterine bleeding, such as heavy or long periods or bleeding in between periods. The 2018 study by Dr. Annabelle Brennan found that “hormone-releasing IUDs is the most effective form of non-surgical treatment for abnormal menstrual bleeding.”

Birth Control Pill

Different types of hormonal contraceptives (birth control pills) can reduce bleeding and related problems. Hormonal contraceptives are medicine for the uterus and can lessen the amount of uterine bleeding.

D&C: Dilation and Curettage

Dilation and curettage (D&C) is a procedure to remove tissue from inside your uterus. Learn more on the Mayo Clinic’s website.

Myomectomy

According to the Mayo Clinic, in a myomectomy, your surgeon removes the fibroids, leaving the uterus in place. This can be performed laparoscopically or via hysteroscopy.

Hysterectomy

Hysterectomy (the removal of the uterus) is 100% effective in stopping uterine bleeding. A hysterectomy is considered a major surgery that requires a hospital stay. Although it will permanently solve uterine bleeding, including heavy periods or bleeding between periods, it also means you won’t be able to become pregnant.

Endometrial Resection or Ablation

Another treatment option is to temporarily remove or cauterize the top layer of the uterine lining (endometrium). Here the tissue is removed using surgical instruments (endometrial resection) or destroyed, for instance, using laser beams or microwave energy (endometrial ablation). After this procedure, you’ll often stop having periods for several years or have much lighter periods. This option can affect future fertility.

Medically reviewed by Dr. Chimsom T. Oleka, M.D, Written by Jane Flanagan — Updated on January 30, 2023.

We hope you found this post informative — but remember: we’re not doctors and this post is not medical advice! While all posts are fact-checked and well researched, we always recommend you chat with your doctor about any questions or concerns you might have regarding a medical condition. We’re here to support and educate, but never with the aim of disregarding professional medical advice you’ve been given. Phew, now that that’s out of the way, you can go on living unapologetically free, and in period underwear.