MTHFR gene mutation test is done to know two relatively common mutations in the MTHFR gene. These mutations are associated with the elevated levels of homocysteine in the blood. This test is ordered to confirm the positive results of an elevated homocysteine test, along with the cardiac risk tests when a person has the family history of cardiovascular disease or when there are inappropriate blood clots (thrombosis). It is not a common test, but it is suggested to be done when there is the presence of homocysteine in the blood.