Frequency analysis of the oral glucose oxygen consumption (VO₂) signal was realized and the spectral density of this signal with the glucose and insulin levels during oral glucose tolerance test (OGTT) was evaluated. The study included 10 control subjects and 12 glucose intolerance patients of ages ranging between 18 and 60 years old. The VO₂ signal was registered and plasma glucose and insulin levels were measured every 10 min during 3 hours. The variance analysis among plasma glucose, insulin concentration and spectral energy of VO₂ was evaluated. Using Pearson correlation, the plasma glucose and insulin values were compared with the spectral energy of VO₂ for each group. Variations in the spectral density of VO₂ were observed after oral glucose load administration during OGTT, however, they did not show statistical significance with the glucose and insulin levels in both analysis. These results contribute to understand the behaviour of the oxidative glucose metabolism in the intolerant patients.