Why Am I Passing Blood Clots Between Periods?


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

Most women have a period on a monthly cycle (on average, the cycle is 28 days). The duration of their period 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 blooding is not considered unusual. However, it’s not considered normal to experience heavy bleeding or to pass clots outside monthly menstruation.

What Is a Period Clot?

The period clots that you see as part of menstruation are different from:

  • Clotting that happens when you cut yourself 
  • Clots that form in veins (that can be potentially life threatening).

Period blood clots are pieces of the endometrial lining that builds up in your uterus in preparation for pregnancy, then are shedded when you don’t conceive.

Because the opening of your cervix at the top of the uterus is narrow, blood may collect at the bottom of your uterus and flow slowly out. If you have a heavy flow, there’ll be more blood collecting at the bottom of the uterus 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.

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.

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

Keep track of the number of pads or tampons 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 experience large clots either during or between periods, it’s something you may need to investigate with your doctor. 

It’s possible that bleeding is an irregular period. But if you are bleeding between periods there may be a number of explanations and causes.

Birth Control Causes

  • 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.
  • Morning-After Pill: According to the Mayo Clinic, the morning-after pill may cause bleeding between periods or heavy menstrual bleeding.
  • Intrauterine Device (IUD): Some women with an IUD for birth control may also experience non-period bleeding.

External Causes

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

Common Infections

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

  • Sexually Transmitted Infection (STI), including chlamydia, gonorrhea, and genital warts cause abnormal bleeding.
  • Pelvic Inflammatory Disease (PID), an infection of the upper part of the female reproductive system.

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 tumours 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 can cause cysts in the ovaries and make it difficult to get pregnant. It may also cause irregular vaginal bleeding.
  • Blood clotting disorders, like von Willebrand disease may cause bleeding.
  • Other health conditions, like hypothyroidism, liver disease, or chronic kidney disease.
  • Cancer: Cancer or pre-cancer 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 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 Clotting

Depending on the cause of intermenstrual bleeding and clotting, 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 (menorrhagia) or by bleeding between periods (metrorrhagia).

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

If you experience heavy vaginal bleeding or clotting outside your period (requiring a tampon or pad), we advise seeking medical advice.

If bleeding or clotting is is accompanied by any of the following symptoms, you'll want to see a doctor immediately:

  • Heavy periods with a lot of clotting.
  • Irregular periods.
  • Abdominal pain or cramping.
  • Pain or a burning sensation when peeing.
  • Unusual vaginal discharge and/or redness and itchiness.

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 inconsistently: 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 visit a 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.

Preparing for Your Medical Appointment

When you see your doctor, they may need to know:

  • How long this has been happening: Is it something you’ve always experienced or did it start recently etc.
  • 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 certain days in your menstrual cycle or seemingly at random?
  • How long did the bleeding last: 1-2 days or more?
  • How heavy was the bleeding: Did you use any protection? Was a panty liner insufficient?
  • 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?

They'll also likely examine you. The tests they might administer will depend on your age and other factors. If you could be pregnant, they'll probably administer a pregnancy test.

They'll also likely order bloodwork to check your blood count and see if you’re anemic.

Other tests 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 causes of abnormal bleeding. Learn more from The Cleveland Clinic.
  • Pelvic Ultrasound: A pelvic ultrasound allows quick 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

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

Some treatment options she might explore with you may include:

Intrauterine Device (IUD)

It may seem unusual that one possible cause of bleeding may also be used as a treatment. But hormone-releasing IUDs can help.

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 can reduce the bleeding and related problems. Hormonal contraceptives affect the menstrual cycle and lessen the amount of 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.


According to the Mayo Clinic, in a myomectomy, your surgeon removes the fibroids, leaving the uterus in place. If the fibroids are few in number, you and your doctor may opt for a laparoscopic


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 option is to remove the lining of the womb (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, or have much lighter periods. This makes pregnancy unlikely.

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