The Acylcarnitines Quantitative Profile using Flow Injection Analysis–Tandem Mass Spectrometry (FIA-MS/MS) is an advanced laboratory test used to measure the levels of fatty-acid and amino-acid–derived acylcarnitines in the human body. This analysis is a valuable tool for diagnosing and monitoring metabolic disorders, such as fatty-acid oxidation defects, which affect the body’s ability to convert fats into energy. The results can reveal abnormal accumulations of specific fatty acids, indicating metabolic disturbances that may require medical intervention. FIA-MS/MS technology is known for its precision and speed, providing comprehensive information about the concentrations of various acylcarnitines in a blood sample, which helps improve the understanding of a patient’s metabolic status. This test is especially important for individuals experiencing unexplained symptoms such as chronic fatigue, muscle weakness, or growth issues, as it assists in guiding appropriate treatment plans and enhancing personalized healthcare.