Factor XI deficiency is an inherited clotting disorder affecting dogs. Factor XI is an essential protein needed for normal blood clotting. Deficiency of this factor most commonly results in a mild bleeding disorder. An affected dog may bruise easily, have frequent nosebleeds, and exhibit prolonged bleeding after surgery or trauma. In rare cases, the bleeding may be severe. Due to the mild nature of this disorder, affected dogs may not be identified until a surgery is performed or trauma occurs at which time excessive bleeding is noted. Veterinarians performing surgery on dogs that are known to have coagulation factor XI deficiency should have ready access to blood banked for transfusions. Most dogs with this condition will have a normal lifespan despite increased blood clotting times.