How severe is haemophilia?

The severity of haemophilia usually depends on the amount of clotting factor present in the blood.

Severe haemophilia: the level of clotting factor in the blood is less than 1%8
Moderate haemophilia: the level of clotting factor in the blood is between 1-5%8
Mild haemophilia: the level of clotting factor in the blood is between 6-40%8

People with severe haemophilia can bleed frequently and often for no apparent reason. This is known as spontaneous bleeding and occurs most commonly in the joints or muscles. People with moderate haemophilia usually bleed less frequently than those with severe haemophilia, and do not usually bleed spontaneously. They may bleed for a long time after injury, surgery or a dental procedure. People with mild haemophilia usually only have prolonged bleeding after serious injury or surgery and may never bleed spontaneously.8