A diagnosis of hemophilia is suspected when prolonged and uncontrolled bleeding occurs in response to trivial injury.

Diagnosis of this condition involves several laboratory tests and an outline of this process is given below:

• A detailed history of bleeding tendencies from immediately after birth is taken. A propensity to bruise easily and  prolonged bleeding in response to minor injury are considered possible indicators of hemophilia.
• A detailed family history is taken and may well suggest that the condition runs in the family.
• Diagnosis is usually suspected based on blood tests that indicate poor coagulation. This is identified by an increased partial thromboplastin time in the context of a healthy prothrombin time and bleeding time. Diagnosis is confirmed if further blood testing reveal a very low level of factor VIII.

The level of Factor VIII does not usually change throughout an individual’s lifetime and the severity of disease a person has ranges from mild to severe depending on how deficient their Factor VIII level is.

Severe hemophilia A is the most common form of hemophilia, accounting for 60% of all cases, and is defined as a Factor VIII level of less than 1%. People with severe hemophila A experience at least 20 or more episodes of severe bleeding every year, sometimes even in the absence of trauma or injury. Moderate hemophilia A is defined as a Factor VIII level of between 1% and 5%, along with less frequent bleeding episodes. Mild hemophilia is defined as a Factor VIII level of between 5% and 25%, with bleeding episodes only occurring in response to severe trauma or surgery, for example.

• Genetic testing is also now available to help determine whether a person is at risk of developing hemophilia or passing the condition on to any offspring.