Objective: To compare the hypoglycemic effect of the aqueous extract of Moringa oleifera (moringa), Smallanthus sonchifolius (yacon) and metformin on Rattus norvegicus, albino variety, with induced diabetes mellitus. Materials and methods: Preclinical, experimental, controlled and randomized study. Diabetes was induced intraperitoneally with a dose of alloxan at 130 mg/kg. A total of 24 male Rattus norvegicus, albino variety, Holfzman strain (6 per group) were used. They were divided as follows: control group (no treatment), metformin group (14 mg/kg), M. oleifera group (200 mg/kg), and S. sonchifolius group (140 mg/kg), treatments were administered via orogastric tube for 15 days. Glycemia levels were determined using an Accu-Chek® Instant electronic glycometer (Roche). Results: Decreased glycemia was observed in the treatment groups: M. oleifera (p = 0.009), S. sonchifolius (p = 0.002) and metformin (p = 0.002), by 313 mg/dL, 281.5 mg/dL and 415 mg/dL, respectively. When comparing glycemia in the treated and control groups, no difference was observed (P > 0.05) at 24 hours and four days of treatment; while at the eighth (P < 0.05) and fifteenth day (P < 0.01) the treated groups had lower glycemia than the control group, but it was similar among them. Conclusion: The aqueous extract of S. sonchifolius, M. oleifera, and metformin presented similar hypoglycemic effect in experimental rats with induced diabetes.