C16 Lactosylceramide-d3 (d18:1/16:0-d3) is intended for use as an internal standard for the quantification of C16 lactosylceramide by GC- or LC-MS. C16 Lactosylceramide is an endogenous bioactive sphingolipid. It forms membrane microdomains with Lyn kinase and the αi subunits of inhibitory G protein-coupled receptors (GPCRs), suggesting a role in cell signaling. Plasma levels of C16 lactosylceramide are elevated in insulin-resistant cattle. C16 Lactosylceramide is also upregulated in a mouse model of Niemann-Pick type C1 disease, a neurodegenerative cholesterol-sphingolipid lysosomal storage disorder.As this product is derived from a natural source, there may be variations in the sphingoid backbone.