BACKGROUND: The liver function tests and noninvasive tests (NITs) play important roles in the follow-up and monitoring of fatty liver disease (FLD). Our aim is to establish annual biological variation (BV) and personalized reference intervals (prRIs) of liver function tests for the first time in order to accurately assess the status and progress of FLD. METHODS: 67 fatty liver patients who participated in regular physical examination once a year for six consecutive years, were enrolled. Based on these patients, we calculated annual BV and derived parameters, including reference change value (RCV), index of individuality (II), and total variation around the true homeostatic set point (TV RESULTS: We calculated the annual within-subject BV (CV CONCLUSION: Annual BV and their derived parameters based on fatty liver patients can provide an objective basis for the monitoring and follow-up of FLD, a global epidemic disease.