Background and Objective: Lactose is a disaccharide sugar and is found in mammals milk and derivatives. Lactose intolerance is the inability to metabolize lactose, because of a lack of the required enzyme lactase in the digestive system. Genetically the physiological hypolactasia (primary LM) is associated with the LCT-13910 C/T and LCT-22018 G/A polymorphisms. The aim of this study focused on the diagnosis and treatment intolerance or malabsorption of lactose in a cohort of 983 patients for the appearance of non-specific symptoms suggestive of a lactose intolerance. Methods: The work was divided into the following phases: diagnosis of lactose intolerance or malabsorption; Check the incidence of primary lactase deficiency in the population Lucana (Italy); Evaluate the improvement of post-diagnosis symptoms and impact on quality of life (Q.O.L: Quality Of Life) as a result of enzymatic and/or food therapy in intolerant subjects. Evaluate the correlation genotype/phenotype studying variants -13910 C>T and -22018 A>G in LPH gene. Results: Of the 983 participants, 668 subjects (67.95%) had a positive homozygous mutation (associated to-13910CC hypolactasic phenotype), 314 subjects (31.94%) had a positive heterozygous mutation (associated to -13910CT lactase persistent phenotype) and only in 1 subject (0,1%) the 2 alleles were not mutated (-13910TT dominant homozygous). The present work reveals a 67.95% of participant with a positive homozygous mutation (-13910CC). Conclusions: The lactose malabsorption is a condition widespread in Italy, but much less frequently is the syndrome of intolerance. Embarking on a diet that a priori excludes milk and derivatives, in the absence of a definitive diagnosis, it can have a negative impact on the welfare of the organism The genetic test is really simple and noninvasive, confirms or excludes a malabsorption and in particular circumstances provides a predictive test to detect primary hypolactasia long before of her clinical manifestation.