Free fatty acids are mainly formed by the decomposition of subcutaneous fat and visceral fat, and are an important source of energy for human metabolism. The level of free fatty acids in human serum is extremely low under normal conditions, and rises transiently during prolonged starvation, strenuous exercise or emotional state, and is easily affected by various endocrine hormone levels. Free fatty acids in human serum mainly include stearic acid, palmitic acid and oleic acid, etc., which are combined with serum proteins and operate in the blood with high metabolic activity. Although they are easily affected by fat metabolism, sugar metabolism and endocrine factors, they are also very sensitive clinical indicators reflecting the metabolism of sugar and lipids as well as the endocrine function of human body. Patients with abnormal free fatty acid test results need to go to the hospital and be diagnosed by a professional doctor.