Many diabetic patients prefer to use herbal medicine and treated with conventional drugs, concurrently. The main objective of this study was to evaluate the co-therapeutic effects of Sidr(Zizyphusspina-christi L.) fruits or leaves and metformin in diabetic rats. Forty two adult male albino rats were used and divided into seven groups (G1-G7). G1 was kept on basal diet (negative control), while other groups were subcutaneously injected with alloxan (120 mg/kg body weight).G2 was kept untreated as a positive control, while the other alloxan -injected groups were treated with metformin (100 mg/kg body weight) as a reference drug (G3), or fed on basal diet supplemented with 5% of either Sidr fruits (SFP) or leaves powder (SLP) (G4 and G5, respectively). G6 and G7 received combined treatments (metformin + SFP and metformin + SLP, respectively). The curative period lasted for 4 weeks. By its end, body weight gain (BWG) and relative weights of liver, kidneys and pancreas were calculated. Fasting glucose, insulin, amylase activity, liver glycogen, lipid profile as well as liver and kidney functions were determined. The typical manifestations of diabetes were noticed in untreated diabetic group including hyperglycemia and hypoinsulinemia.Moreover, a significant increase in serum amylase activity and relative liver and kidney weights was noticed associated with dyslipidemia, liver and kidney dysfunction and a significant decrease in BWG and absolute pancreas weight along with marked histopathological abnormalities in pancreas tissue.SFP was more effective than SLP in normalizing body weight, pancreas weight and liver antioxidant status, while the capability of SLP was higher in correcting the level of serum low density lipoprotein cholesterol (bad cholesterol). In general, receiving combined treatments was more efficient than receiving metformin alone.In conclusion, Sidr fruits and leaves can help metformin in the treatment of diabetes mellitus.