Hemophilia is divided into three classes: severe, moderate and mild. The severity, and thus seriousness of the symptoms, is based on the amount of active clotting factor in the blood. The normal amount of clotting factor an individual maintains generally varies between 50% and 150%. Whereas, individuals diagnosed with Hemophilia have less than 50%.

Individuals with Mild Hemophilia have active clotting factors vary from 6% to 50%. These individuals rarely experience a bleeding problem and may bleed only after severe injury.

Individuals with Moderate Hemophilia have between 1% and 5% active clotting factor. These individuals have fewer bleeds than individuals with Severe Hemophilia, usually bleeding only as a result of injury.

Individuals with Severe Hemophilia have less than 1% active clotting factor. As a result, they are subject to the greatest number of bleeds, often several per month, and may bleed spontaneously.

All individuals with hemophilia must take appropriate precautions when having dental work or surgery performed. Factor level and severity do not change over the life of an individual. Moreover, the severity of factor deficiency tends to be familial; relatives will often show similar factor levels and severity.