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Factor XI Deficiency

Factor XI (11) deficiency is an inherited bleeding disorder. It is caused when a person’s body doesn’t produce enough of protein in the blood (factor XI or FXI) that helps blood clot or the factor XI doesn’t work properly. Unlike haemophilia A or B, there is no bleeding into joints and muscles.

Factor XI deficiency is the most common of the rare bleeding disorders, estimated at one in 100,000 people, and is the third most common bleeding disorder to affect women after von Willebrand disease and haemophilia.

Factor XI deficiency used to be known as haemophilia C.

Links to selected resources:

What Is Factor XI Deficiency?
(World Federation of Hemophilia)
Explains the causes of this bleeding disorder, its symptoms, diagnosis and treatment.

Factor XI deficiency (Hemophilia C)
(Canadian Hemophilia Society)
Explains factor XI deficiency, what causes it, how it is passed on, how common it is, diagnosis, symptoms and treatments.

Factor XI deficiency
(National Hemophilia Foundation, USA)

Factor XI deficiency
(National Organisation for Rare Disorders/NORD)


Pre-pregnancy planning if you have factor XI deficiency 
(Factored In, HFA)

Source: What are rare clotting factor deficiencies? World Federation of Hemophilia: Montreal, 2023.

NB We provide these links as a service to the haemophilia community. As web sites can change or should you find a site to be no longer active please notify hfaust@haemophilia.org.au. Haemophilia Foundation Australia is not responsible for the content of any external web sites. The featuring of a site on this page is not an endorsement by HFA of the information or views expressed therein.

Date last reviewed: 1 February 2024

Important Note: This information was developed by Haemophilia Foundation Australia for education and information purposes only and does not replace advice from a treating health professional. Always see your health care provider for assessment and advice about your individual health before taking action or relying on published information. This information may be printed or photocopied for educational purposes.

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