Tricosanoic acid-d3 is the deuterium-labeled form of tricosanoic acid. Tricosanoic acid (C23:0) is a long-chain saturated fatty acid and an endogenous agonist of the free fatty acid receptor FFAR1, known to stimulate hair growth. It enhances cognitive function through mechanisms such as regulating neuronal membrane fluidity, inhibiting neuroinflammatory responses, participating in myelin formation, and influencing neuronal energy metabolism. In Alzheimer's disease (AD) models, particularly in the prefrontal cortex, lower expression levels of tricosanoic acid are observed, while higher serum concentrations are correlated with improved cognitive performance. Tricosanoic acid may serve as a biomarker for diseases associated with cognitive decline.