Leaf infusions from B. monandra have been frequently used in popular medicine to treat diabetes. In the current work, it was investigated the acute effect of Bauhinia monandra leaf lectin, BmoLL, galactose specific, on glucose and insulin levels of control (C) and pre-natal malnourished (M) Wistar rats. M and C rats were obtained from females kept on multideficient and standard diets. Rats (13 to 16 weeks) were submitted to glucose tolerance test, through an overload of glucose (1.5 mg/kg, po.) and divided into 4 sub-groups: C and M receiving vehicle (V, 0.1% DMSO, 2.5 ml/kg, po), CV and MV (n=4); C and M receiving BmoLL (150 mg/kg, po.), CBmoLL and MBmoLL (n=5). Basal fasting serum glucose (SG) and serum insulin (SI) levels were measured. Lipid levels, aspartate (AST) and alanine aminotransferase (ALT), urea and hematological determination were also evaluated. Basal fasting SG (171 ± 16.6 vs.128 ± 10.5 mg/dl, respectively; p< 0.05) was higher in M than in C. Glucose tolerance curve (GTC) was higher (p< 0.05) in MV than in CV. Basal SI was the same for C and M. CBmoLL showed a peak of SI in the first hour after glucose overload (3.0 ± 0.6 µIU/ml), while CV did it in the second hour (4.0 ± 1.2 µIU/ml). In MV and MBmoLL SI peak occurred at second hour. Differently from CBmoLL, MBmoLL presented low levels of insulin at fourth hour (2.9 ± 1.1 vs. 0.2 ± 0.01 µIU/ml, respectively; p < 0.05). ALT and urea were the same for C and M (61 ± 2.4 vs. 54 ± 3.6 and 35 ± 1 vs. 37 ± 1.4 IU/L, respectively). Cholesterol and triglycerides were lower in C than M (29 ± 1.3 vs. 35 ± 1.7; 76 ± 9.6 vs. 133 ± 12.8 IU/L, respectively; p < 0.05). Hematological profile was the same for C and M. Together, these data suggested that M revealed glucose intolerance and lectin did not change serum insulin or glucose in M or C rats.