Familial hypercholesterolemia (FH) is a genetic disease that is massively underdiagnosed worldwide. Affected patients are at high risk of cardiovascular events at young ages. Early intervention in childhood could help prevent heart attacks and cerebral strokes in these patients. We conducted an interventional study including 10 patients that previously underwent genetic testing for familial hypercholesterolemia. These patients received lifestyle and diet recommendations that they followed for a year before being reevaluated. Patients with negative genetic testing were able to achieve lower levels in their lipid panel values compared to the patients with positive genetic testing, with lifestyle changes alone. LDL-cholesterol levels decreased by 18.5% in patients without FH while patients genetically confirmed with FH failed to achieve lower LDL-cholesterol levels without medication. Genetic testing for FH is not always part of screening algorithms for FH. Some studies even advise against it. Our study proved the importance of genetic testing for FH when suspecting this disorder and choosing the treatment course for patients.