Understanding what stage of leptin resistance you have helps to determine how easy it will be for you to lose weight and how long it will take to get to your target goal. You can assess your stage of leptin resistance by checking your serum leptin level. You will want to check your serum leptin level in the FASTED state. Once you have your result you can then determine your stage by looking at the stages below: Stage 1 (mild leptin resistance): serum leptin between 10-19 ng/ml. - At this stage,