The aim of this study was to present the properties of insulin sensitivity indices formulas to justify selection of formulas to evaluate of insulin sensitivity for calculation from an oral glucose tolerance test (OGTT) data. Twelve of the most applicable formulae for ISI calculation were analyzed in the view of two sets of results: 1) point contrasts, calculated as the ratio of average ISI values in lean and obese groups of patients; and 2) interval contrasts, calculated as ratios of T from the two-sided t-test, evaluated as dimensionless, mutually comparable contrasts within a continuous scale. Statistical significance of individual ISIs in terms of their contrasts was evaluated by two-sided t-tests. P<0.001 was a considered statistically significance between a group of 59 healthy volunteers with BMI<25 kg/m2 and a group of 63 volunteers with BMI≥25 kg/m2 who underwent frequent OGTT sampling. To compare data of an individual subject with the standard, we recommend selecting the formulas with a high point contrast. To compare of data of several subject groups, we recommend using the formulas with a high interval contrast.