Familial chylomicronemia syndrome (FCS) is a disorder characterised by severe hypertriglyceridemia (HTG), caused by mutations in five canonical genes, primarily the lipoprotein lipase (LPL) gene. Scores used to identify FCS show inconsistencies with genetic results, and measuring LPL activity could be a complementary diagnostic tool, requiring standardised methodologies and reference values (RV). The objective of this work was to review the literature on LPL activity in FCS, integrating our findings. In patients with HTG, it was to identify FCS and distinguish it from multifactorial forms (MCS) by measuring LPL activity using a reference method and RV established in our laboratory. Ten patients with HTG were evaluated and classified as very likely (≥10), unlikely (≤9), and very unlikely (≤8) for FCS according to the Moulin score. In 22 normotriglyceridemic controls, the RV for LPL activity was determined. Enzymatic activity in plasma post-heparin injection, with and without enzymatic activators, was measured, and genetic analyses were performed using saliva samples.The RV for LPL activity was 33.3 (18.7–70.3) mUI, with 6.6 mUI (20% of RV) used as a differential criterion between FCS and MCS. Of seven patients with Moulin scores ≥10, four had genetic findings incompatible with FCS. Among these, two showed LPL activity <20%, and two had activity >30%. In patients with Moulin scores <10 and inconclusive genetic diagnoses, LPL activity was >20%. LPL activity could differentiate FCS from MCS, particularly in cases without genetic confirmation, highlighting the importance of specialised laboratory analysis.