Obesity and dyslipidemia are often found in association with insulin resistance (IR). These components combined with hypertension characterize the most common endocrine disorder in humans, the metabolic syndrome. Thus, in addition to profiling body weight evolution and lipid metabolites, glucose tolerance (a reflection of IR) and insulin sensitivity should also be considered as part of any metabolic phenotyping protocol. The ability to measure IR and glucose tolerance is important not only in the quest to fully understand the pathogenesis of the metabolic syndrome in the mouse, but also to test the effects of potential interventions. This unit presents a variety of tests used for this purpose, including direct blood glucose measurements, insulin measurement by ELISA, the homeostatic model assessment, glucose tolerance and insulin sensitivity tests, and the euglycemic clamp.