Insulin resistance (IR) is a widespread health problem characterized by failure of cell responses to insulin. IR increases the risk of fungal infections. Long-term administration of dexamethasone is a therapeutic need accompanied IR and fungal infections. Fluconazole is the first-line antifungal therapy that inhibit fungal cytochrome P450 (CYP450) enzyme. It has a hepatotoxic effect and moderate inhibitory effect on multiple CYP450 enzymes that could affect the pharmacokinetics of drugs used to treat insulin resistance such as metformin. This study aims to evaluate the effect of administration of fluconazole on liver function, CYP450 concentration and level of insulin resistance induced by dexamethasone and high fat diet. Insulin resistance in rats was induced by dexamethasone (0.1mg/kg/day s.c) (DEX) for 2 weeks, after eight weeks of high fat diet (HFD) until the end of the experiment. Oral administration of fluconazole (20, 40 mg/kg) (FLU20, 40) was started concomitantly with DEX for 2 weeks. Metformin (400mg/kg) (MET) was used as a reference treatment for IR and administered orally for 2 weeks with DEX and FLU (20, 40). Concomitant administration of FLU either 20mg/kg or 40 mg/kg with DEX showed significant increase in IR, AST and ALT compared by that caused by DEX alone or with MET. FLU showed a significant decrease in serum CYP450 that elevated by DEX. Massive fibrosis was noticed in histological assessments of liver tissues of HFD+DEX+FLU (20, 40) groups. In conclusion administration of FLU in case of IR induced by HFD+DEX resulted in deterioration of liver functions and decrease in the therapeutic efficacy of MET.