Oleoyl Ethanolamide-d4 (OEA-d4) is primarily used in research and analytical studies as a stable isotope-labeled internal standard. It plays a crucial role in the quantification and analysis of oleoyl ethanolamide (OEA) in biological samples using techniques like liquid chromatography-mass spectrometry (LC-MS). By providing a reference point, it ensures accurate measurement of OEA levels, which is essential for studying its physiological effects, such as its role in appetite regulation, lipid metabolism, and anti-inflammatory processes. Additionally, OEA-d4 aids in investigating the endocannabinoid system and its interactions with various metabolic pathways, contributing to advancements in metabolic and neurological research.