Curcumin is the most active component of turmeric. It is believed that curcumin is a potent antioxidant and anti-inflammatory agent. Tetrahydrocurcumin is one of the major metabolites of curcumin that exhibits many of the same physiologic and pharmacological activities as curcumin and in some systems may exert greater antioxidant activity than curcumin. Oral administration of tetrahydrocurcumin at 80 mg/kg body weight to diabetic rats for 45 days resulted in a significant reduction in blood glucose and significant increase in plasma insulin levels. In addition, the diabetic rats had decreased levels of plasma total protein, albumin, globulin and albumin/globulin ratio as compared to control rats. After treatment with tetrahydrocurcumin and curcumin total protein, albumin, globulin and albumin/globulin ratio were brought back to near normal. The activities of hepatic and renal markers were significantly elevated in diabetic rats as compared to control rats, and treatment with tetrahydrocurcumin and curcumin has reversed these parameters to near normal levels. In diabetic rats, the decreased levels of urea, uric acid and creatinine with increased levels of albumin and urine volume was observed, and treatment with tetrahydrocurcumin and curcumin reversed these parameters to near normal. Tetrahydrocurcumin appeared to have a better protective effect when compared to curcumin.Diabetes mellitus is by far the most common of endocrine disorders and a major threat to health care worldwide. The increase of free radical-mediated toxicity is well documented in streptozotocin-diabetic rats. The liver is the main effector organ for maintaining plasma glucose levels within narrow limits. Hyperglycaemia can generate a redox imbalance inside the cells, especially in the liver [1]. A model antidiabetic drug should possess both hypoglycaemic and antioxidant properties, without any adverse effects. Plant drugs are frequently considered to be less toxic than synthetic ones [2].The liver and kidney play a major role in the pathogenesis of type 2 diabetes. The liver enzymes aspartate transaminase, alanine transaminase, alkaline phosphatase and γ-glutamyl transpeptidase are used routinely for assessing liver function. Although they are present in tissues throughout the body, they are most often elevated in patients with liver diseases or high alcohol consumption. Nephrotoxicity is one of the major side effects of drug therapy in clinical practice, frequently leading to acute renal failure. Many physiological mechanisms have been implicated in streptozotocin-induced renal injury in diabetes [3].Curcumin (diferuloylmethane) is the substance that gives the spice turmeric, which is extensively used in Indian cuisine as a component of curry powder, providing its yellow colour. It is believed that curcumin is a potent antioxidant and anti-inflammatory agent. Curcumin has been shown to reduce the hyperlipidaemia [4], delay the development of cataract [5], ameliorate renal lesions [3] and reduce crosslinking of collagen [6] in a stre...