Prophylaxis is the regular use of clotting factor concentrates to prevent bleeds before they start.

Injections of clotting factor are given one, two or three times a week to maintain a constant level of factor VIII or IX in the bloodstream. Prophylaxis can help reduce or prevent joint damage.

In countries with access to adequate quantities of clotting factor concentrates, this is becoming the normal mode of treatment for younger patients, and can be started when the veins are well developed (usually between the ages of two and four years).