Individuals who carry the Factor V Leiden mutation have a 3- to 8-fold increased risk as heterozygotes and a greater than 10-fold increased risk as homozygotes.
Individuals who carry the F2 prothrombin mutation have a 2- to 5-fold increased risk as heterozygotes and up to a 10-fold increased risk as homozygotes.
Individuals who carry two copies of the 677C>T mutation, or one 677C>T and one 1298A>C mutation, in the MTHFR gene have between a 2- and 8-fold increased risk.
Compound heterozygotes (heterozygous for more than one of the mutations tested for) have an even higher risk of thrombophilia. For example, a person that is heterozygous for both the Factor V Leiden mutation and heterozygous for the F2 prothrombin mutation has a greater than 20-fold increased risk.