Hemophilia and inhibitors

PDF download is not available for Arabic and Urdu languages at this time. Please use the browser print function instead

Inhibitors are a type of immune complication that some people with hemophilia may develop. Learn more about inhibitors and how they are treated.


Another type of complication that can affect your treatment plan is related to your immune system. Normally, your immune system helps protect your body against disease and infection by producing antibodies. Antibodies recognize and destroy any substance that shouldn’t be there, such as viruses or bacteria.

Sometimes people with hemophilia produce antibodies against the replacement factor that is given for treatment. Antibodies that target and destroy factor are called inhibitors. A person with hemophilia and an inhibitor has a hard time treating their bleeds with factor because their immune system destroys factor as soon as it is infused.

Inhibitors usually develop in people with severe hemophilia A. They often develop during the first 50 treatments of factor replacement therapy. Doctors usually find out whether you have inhibitors through a routine blood test. Even if you do not have inhibitors, it is still important to understand what they are and how they can affect hemophilia treatment. People with hemophilia with inhibitors often need other types of treatments to help stop the bleeding.

Remember how the clotting cascade works? For a quick review, click through the animation in the Understanding blood clotting page in Module 2.

Last updated: March 13th 2019