The aim of this randomized and double blinded pilot clinical trial was to investigate the anti-diabetic efficacy of the Rauvolfia-Citrus (RC) tea in humans. We have earlier shown that a combination of calorie-restriction and chronic administration of the RC tea to the genetic diabetic (BKS-db) mice resulted in the normalization of blood sugar, reduction in lipid accumulated in the mice eyes and prevention of the degeneration of the otherwise brittle BKS-db pancreas. The tea is made by boiling foliage of Rauvolfia vomitoria and fruits of Citrus aurantium and is used to treat diabetes in Nigerian folk medicine.