This study aimed to perform an experimental analysis of the two most common substitutions of the LDLR gene, c.1775G > A p. (Gly592Glu) and c.662A > G p. (Asp221Gly) as well as c.91G > A p. (Glu31Lys) and c.2483delA p. (Tyr828Phefs∗101) stop loss alteration detected in the Polish population to reclassify the variants, which is essential for the correct diagnosis of FH patients. The gene discussed is LDLR; the disease is familial hyperaldosteronism.