Can Fibroids Cause Blood Clots? What Every Woman Should Know

Many women assume that heavy periods with blood clots are simply part of having fibroids, but that is not something you have to accept as your normal. Bleeding from fibroids has clear causes, and there is a range of treatment options to consider. 

Knowing the difference between what is normal and what is not can help you seek the right support sooner. 

What are uterine fibroids?

Uterine fibroids are benign (not cancerous) growths made of muscle and fibrous tissue that develop in or on the uterus. Fibroids are very common, especially in women in their 30s and 40s. Hormonal changes in oestrogen and progesterone, as well as genetics, are thought to play a role in their development. 

Fibroids are grouped based on where they grow in or around the uterus:

• Submucosal fibroids grow just beneath the inner lining of the uterus. These are most closely linked to heavy periods and clotting.

• Intramural fibroids grow within the muscular wall of the uterus and are the most common type.

• Subserosal fibroids grow on the outer surface of the uterus and tend to press on surrounding organs.

• Pedunculated fibroids grow on a stalk, either inside or outside the uterus.

Knowing which type you have matters because it can influence your symptoms and the treatment options your doctor may recommend.

What are menstrual blood clots?

In this article, “blood clots” refers mainly to menstrual clots passed during a period. These are different from blood clots that form inside veins, such as deep vein thrombosis. In rare cases, very large fibroids may contribute to vein compression, but menstrual clots themselves do not travel to the lungs or brain. 

Each month, your body sheds the lining of the uterus, known as the endometrium. For most women, this happens roughly every 21 to 35 days.

Throughout the month, oestrogen causes this lining to grow and thicken in preparation for a possible pregnancy. If pregnancy does not occur, the lining sheds and menstruation begins. The blood and tissue then pass through the cervix and out of the vagina.

To help the flow move freely, your body releases natural substances that thin the blood. However, when bleeding becomes heavy and fast, your body cannot thin the blood quickly enough, and clots begin to form. They are most common during the heaviest days of your period, particularly at the start, and usually settle as your flow lightens over the following days.

Why do fibroids cause blood clots?

Fibroids can make your periods heavier and more prone to clotting in a few ways. Understanding why this happens can help make sense of your symptoms.

A larger area of lining to shed 

Fibroids, particularly submucosal fibroids, can increase the surface area of the uterine lining. A larger lining means more blood and tissue is shed with each period. Fibroids can also cause abnormal blood vessels to develop in the uterine lining, which tend to bleed more easily and contribute to the overall volume of blood lost.

Disrupted uterine contractions

Normally, your uterus contracts rhythmically during your period. These contractions help compress blood vessels and limit bleeding. Fibroids can interfere with this process, making it harder for your uterus to control blood loss effectively.

An enlarged uterine cavity 

Fibroids can cause the uterus to become larger overall. This increases the total surface area of the lining that needs to be shed each month, which further contributes to heavier flow and more clotting.

These factors together explain why periods in women with fibroids often tend to be notably heavier than usual.

Passing frequent or large blood clots during your period can feel worrying, especially when bleeding becomes heavier over time. Request an appointment with Thomson Medical for an assessment of your fibroid size, location, and possible causes of heavy menstrual bleeding.

Normal vs abnormal clotting

Not all clots are a cause for concern. Clotting can be a normal part of menstruation, particularly on heavier days.

Normal clotting may look like this:

• Smaller than 2.5 cm

• Occurs occasionally, usually at the start of your period

• Bright or dark red in colour

Abnormal clotting may look like this:

• Larger than 2.5 cm

• Happens frequently throughout your period

• Requires you to change a sanitary pad or tampon every one to two hours

• Comes alongside severe pain, persistent fatigue, or signs of anaemia

Many women live with heavy periods and clots for years without realising these symptoms may be worth discussing with a doctor. Clot size, how often they occur, and how you feel during your period all matter when building a fuller picture.

What symptoms can occur with fibroid-related blood clots?

Heavy periods and clots are often the most visible signs of fibroids, but they are not always the only ones. You may also notice other changes in how your body feels, particularly around the time of your period.

Pelvic pain or cramping 

You might feel intense cramping in your lower abdomen or pelvis. This happens as your uterus works harder to shed a thickened lining. The pain can feel different from ordinary period cramps and may last longer than usual.

Fatigue and anaemia 

Losing large amounts of blood each month can lead to iron deficiency anaemia. You might feel unusually tired, weak, or short of breath, even when you have not been particularly active. These are signs that your body may not be getting enough iron and are worth raising with your doctor.

Prolonged or irregular bleeding 

Because fibroids can disrupt normal uterine contractions, your period may last longer than usual or become harder to predict from month to month.

If any of these symptoms sound familiar, it is a good idea to bring them up with your doctor. Writing down your symptoms before your appointment can help your doctor get a clearer picture.

How is this diagnosed?

Your doctor will usually begin with a few straightforward assessments to understand what is causing your symptoms.

They may then recommend:

• A pelvic examination to check for any changes in the size or shape of your uterus

• A transvaginal ultrasound, an internal scan that uses sound waves to identify the location and size of your fibroids

• Blood tests, particularly a full blood count, to check whether blood loss has led to anaemia

In some cases, further investigations may be needed. Your doctor might suggest an MRI scan or a procedure called a 'hysteroscopy' (which allows a closer look at the inside of the uterus) to assess other conditions, such as polyps, adenomyosis, hormonal changes, bleeding disorders, pregnancy-related causes, medication effects, or, less commonly, cancer of the uterus or cervix.. 

These additional steps help your doctor build a fuller picture before discussing the options that best suit your situation. 

Treatment options for fibroid-related blood clots

Treatment is not the same for every woman. Each treatment has its own benefits, limitations, possible risks, and recovery considerations. Your doctor will consider your symptoms, the size and location of your fibroids, your age, and whether you plan to have children in the future. 

Managing heavy bleeding

Heavy bleeding caused by fibroids can often be managed separately from the fibroids themselves. This is particularly helpful when symptom relief is needed while further treatment decisions are being made.

These options focus on easing your symptoms and supporting your general health:

• Pain relief such as ibuprofen can help reduce discomfort during your period, but it is not suitable for everyone 

• Iron supplements to replenish iron lost through heavy bleeding and support your energy levels

• Hormonal therapy including the contraceptive pill, hormonal injections, or a hormonal intrauterine device (IUD), which can help regulate your cycle and reduce bleeding over time

• Endometrial ablation, a procedure that destroys the uterine lining to reduce heavy bleeding. This may not be not suitable if you plan to become pregnant in the future 

• Tranexamic acid, a non-hormonal medicine that can reduce heavy menstrual bleeding in suitable patients

These treatments do not remove fibroids themselves, but they can help reduce the impact heavy bleeding has on daily life while further treatment is being considered.

Treating the fibroids directly

Some treatments focus on the fibroids themselves by shrinking them, destroying fibroid tissue, or removing the fibroids entirely. 

Depending on your symptoms and future fertility plans, your doctor may discuss: 

• GnRH agonists:

  • Medicines that temporarily lower oestrogen levels

  • May help shrink fibroids and reduce heavy bleeding

  • Often used in the short term, typically for 3 to 6 months, or before surgery

• Uterine artery embolisation (UAE):

  • A minimally invasive procedure that blocks the blood supply to fibroids using tiny particles

  • Causes fibroids to shrink gradually over time

• Laparoscopic or robotic myomectomy:

  • Removes fibroids through small abdominal incisions using a camera and specialised instruments

  • Usually involves a shorter recovery time than open surgery, though it depends on the size, number, and location of the fibroids, as well as your overall health and surgical plan 

• Abdominal myomectomy:

  • Removes fibroids through a larger abdominal incision

  • Often considered for large, multiple, or deeply positioned fibroids

• Hysterectomy:

  • Surgical removal of the uterus

  • As the uterus is removed, fibroids cannot return

  • Usually discussed when other treatments have not worked or are not appropriate

Your doctor will explain the benefits, limitations, and suitability of each option so that treatment decisions can be shaped around your symptoms, fibroid type, and future plans.

When should you see a doctor?

Heavy periods and large clots can become so familiar that they feel normal, but they are not something you simply have to accept. 

Speak to your doctor if you notice any of the following:

• Bleeding that soaks through a sanitary pad or tampon every one to two hours

• Passing clots larger than 2.5 cm across

• Periods that last longer than seven days

• Bleeding between your periods

• Severe pelvic pain alongside heavy bleeding

• Signs of anaemia such as a racing or fluttering heartbeat, dizziness, feeling lightheaded, fainting, or ongoing fatigue

Heavy periods and blood clots can affect your daily life, your energy, and your overall health. Your doctor can help you explore the options available and find an approach that suits your symptoms and your plans for the future.

If your periods have become heavier, longer, or more painful than usual, request an appointment with Thomson Medical to better understand what may be causing your symptoms and what treatment options may help.

FAQ

Are blood clots common with fibroids?

Yes, blood clots can occur with fibroids, particularly when fibroids cause heavy menstrual bleeding. When bleeding becomes heavier than usual, your body may not be able to thin the blood quickly enough before it passes, which is how clots form.

How large is too large for menstrual clots?

Clots larger than 2.5 cm are generally considered unusually large and should be discussed with a doctor, especially if they occur frequently or come alongside heavy bleeding.

Can fibroids cause clots outside of periods?

Yes, fibroids can sometimes cause bleeding between periods, known as intermenstrual bleeding, and clots may occasionally be passed during these episodes.

Do clots mean fibroids are getting worse?

Not always, but increasing clotting or heavier bleeding may suggest that fibroids are growing or affecting the uterine cavity more. Speaking with your doctor can help you understand whether anything has changed.

Can fibroid treatment reduce blood clots?

Yes, treatment for fibroids may help reduce heavy bleeding and menstrual clotting. Hormonal therapies, minimally invasive procedures, or surgery can each play a role in managing symptoms, depending on the type and size of your fibroids.

When is clotting considered an emergency?

Can birth control reduce clotting from fibroids?

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice based on your unique situations, please consult a specialist at Thomson Medical. Request an appointment with Thomson Medical today.