Why Fibroids cause heavy periods

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Why do fibroids cause heavy bleeding, clots and long periods?

It is thought that over 50% of women diagnosed with fibroids experience heavy periods. For some women, this includes large blood clots - larger than a 50p coin according to NHS England - or flooding, which is 2 or more tampons/pads in less than 1 hour. Fibroids can also cause longer periods, bleeding in between periods or even continuous bleeding.

It’s important to note, not everyone is affected the same way, and sometimes heavy periods can be unrelated to fibroids.

Doctors understand several key reasons why fibroids can lead to these problems.

Womb lining not shedding properly

Even small fibroids that grow in the womb can stop the womb lining from shedding properly during a period. This can cause heavy bleeding, long periods, or continuous bleeding that is hard to control. This is one of the most strongly proven causes of abnormal bleeding linked to fibroids.

Increases in the amount of bleeding tissue

Fibroids can stretch the womb and create a larger area of lining that bleeds each month. More lining means more blood loss, which can lead to heavy bleeding and clots or prolonged bleeding, especially when there are several fibroids.

Weak blood vessels

Fibroids can cause extra blood vessels to grow in and around the womb. These blood vessels may be larger and more fragile, so bleeding can be heavier once it starts. This can explain heavy bleeding and clots and why bleeding may feel harder to stop.

Fibroids can stop the womb from tightening properly

During a normal period, the womb tightens to help slow bleeding. Fibroids can interfere with this process, meaning blood vessels stay open longer. This can cause long periods, prolonged bleeding, or bleeding that feels non-stop.

Changes to how the womb lining reacts to hormones

Fibroids can affect how the womb lining responds to hormones, even when hormone blood tests are normal. The lining may become thicker or bleed more easily, leading to abnormal bleeding, heavy periods, or unpredictable bleeding patterns.

Slower clotting

Some studies show that bleeding linked to fibroids may clot more slowly inside the womb. This does not mean someone has a blood disorder, but it can lead to heavy bleeding and clots or periods that last longer than expected.

Important things to know about fibroids and heavy bleeding

Fibroids do not always cause heavy periods.

Location matters more than size, small fibroids can still cause heavy bleeding.

Heavy or prolonged bleeding can have other causes, not just fibroids.

While common, none of these symptoms are normal. If you are experiencing heavy periods of any kind, visit your GP to discuss it.

Are heavy periods disrupting your life?

Do not suffer in silence. If you are experiencing heavy periods we strongly advise you consult your GP if you have not already done so.

However, medication and surgery are not the only tools to assist you on this journey. That’s why we’ve spent time specially curating period products to help you on those especially heavy flow days. To see our recommended range of products, click here.

You are not alone

75-80% of women have fibroids between the ages of 35-55. It is thought between 70-150 thousand women are diagnosed each year in the UK.

There is no shame discussing this with your peers, it helps build awareness and drive change.

Medical disclaimer - This information is for education only and is not a diagnosis or medical advice. Heavy bleeding, long periods, bleeding in between periods, or non-stop bleeding should always be checked by a GP or healthcare professional. They can arrange scans or tests to find the cause and discuss the right treatment options for you.