If an injury occurs in the body, it is normal for a blood clot to form to stop the bleeding and for this the body needs platelets or proteins that are called clotting factors.
Factor VIII and factor IX deficiencies are the most common to present, and are known as hemophilia A and hemophilia B respectively.
While insufficient clotting could lead to abnormal bleeding (hemorrhage), too much clotting could lead to blood clots (thrombosis).
These problems can be hereditary, they can also be caused by liver diseases, by a lack of vitamin K in the body or by a side effect of certain medicines such as anticoagulants.
With fewer diagnoses, the blood may also be deficient in other factors such as I, II, V, V + VIII, VII, X, XI or XIII.