If the bleeding is more rapid than vWF can be generated then a dog will not clot normally and will have excessive bleeding when the vWF is exhausted. The lower the assay for vWF is, the more likely the individual is to bleed with any given event. Major events, such as trauma followed by major surgery, may exhaust the vWF in animals that have higher assays including some carriers. They do not commonly bleed spontaneously but are at great risk to bleed due to injury or surgery. It is not rare for an affected dog to have minor surgery, such as a neuter, or trauma and to not bleed excessively.
Carriers have one normal gene and one mutated gene.
This level will vary over time with any given dog and vary greatly between dogs. Carriers rarely bleed except at times of great stress to their clotting system. Normals have two normal genes. It should be noted that in the event of a prolonged stress to the clotting system, such as very long surgery or a bleeding ulcer, normal dogs and humans would exhaust their vWF and other clotting factors so that they have a prolonged bleeding time. This is treated with transfusion of platelets and clotting factors.