Plasma desmosterol analysis by Gas Chromatography–Mass Spectrometry (GC-MS) is an advanced laboratory procedure designed to measure desmosterol levels, an important compound present in the body as an intermediate in cholesterol synthesis. The significance of this analysis lies in its role in assessing individual health and diagnosing certain conditions related to lipid disorders. The process begins with collecting a plasma sample and processing it to extract desmosterol. The sample is then analyzed using gas chromatography to separate the compound from other components, followed by mass spectrometry to accurately identify and quantify it. This technique is reliable and rapid, providing precise results that help physicians make informed treatment decisions. The analysis is used in multiple fields, including precision medicine and scientific research, enhancing the understanding of lipid balance in the body and its impact on overall health.