Cotinine analysis by liquid chromatography–tandem mass spectrometry (Cotinine, by Liquid Chromatography–Tandem Mass Spectrometry - LC-MS/MS) is a precise test used to measure cotinine levels, which is a major metabolite of nicotine, in a blood or urine sample. This analysis is considered an effective tool for assessing exposure to smoking or the use of tobacco products, whether through direct smoking or indirect exposure to smoke. The importance of cotinine testing lies in its ability to provide accurate information about nicotine consumption, which supports public health research, studies on the health effects of smoking, and smoking cessation programs. This test is usually performed on urine samples, as cotinine levels are a reliable indicator of recent nicotine use. Due to its high accuracy, this analysis is used in a wide range of applications, including patient monitoring, evaluation of treatment effectiveness, and epidemiological studies.