Investigations conducted in our laboratory have shown that transdermal delivery of insulin has several potential advantages over the conventional route. These pectin-insulin (PI)-containing dermal patches possess the ability to maintain sustained controlled release of insulin into the bloodstream of streptozotocin-induced diabetic rats with concomitant reduction of blood glucose levels. We have successfully formulated and optimized the concoction of the PI-containing dermal patch which exhibited improved therapeutic efficacy in glycaemic control mediated by prolonged plasma insulin concentrations in the therapeutic range. Previous studies have shown that the PI-containing dermal patch formulation (33.60 µg/kg) derived from a combination of two 16.80 µg/kg patches prepared with 4 g of pectin is the optimum and chemically stable dermal formulation. Accordingly, the current study was designed to evaluate the chronic treatment of the optimized PI-containing dermal patch on selected metabolic parameters in separate groups of STZ-induced diabetic rats. Dermal patches containing 4 g of pectin and a total insulin concentration of 33.60 µg/kg were formulated by dissolving pectin/insulin in deionised water with subsequent solidification with CaCl2. Animals were treated twice daily 12 h apart for the 5-week experimental period. Blood glucose concentrations and physical parameters (food and water intake, urine output and body weight) were measured weekly. Blood samples were collected for insulin, glycated haemoglobin and antioxidant activity determination. Our findings show that the optimized PI-containing dermal patch reduces blood glucose concentrations with concomitant increase in plasma insulin concentrations. Furthermore, glycated haemoglobin levels were significantly reduced and endogenous antioxidant enzyme activity was increased as a result of improved glycaemic control. The findings of the current study suggest that the PI-containing dermal patch formulation has improved therapeutic efficacy in the alleviation of diabetes mellitus and associated complications. These findings are of significant importance as the PI-containing dermal formulations can be developed into unit dosage forms with prolonged therapeutic efficacy.