Diabetes mellitus is a metabolic syndrome considered one of the life-threatening diseases in the last two decades. This research aimed to investigate the anti-diabetic potential of bitter honey collected from Nilgiris using both in vitro and in vivo methods. The mineral content of bitter honey was also estimated using atomic absorption spectrophotometer. Bitter honey had a higher amount of zinc and copper, while heavy metals like lead, nickel, and cadmium were below the detection limit. The in vitro antidiabetic study was performed using alpha-amylase and alpha-glucosidase inhibition methods. Acute toxicity (OECD 423) was conducted in female Wistar rats to determine the lethal dose of bitter honey. The antidiabetic activity was carried out in type-2 diabetic Wistar Albino rats induced with streptozotocin and nicotinamide. The experimental rats were categorized into five groups (n=8): the normal group, the diabetic control group, standard glibenclamide-treated diabetic group, bitter honey 200 mg/kg, and 400 mg/kg b.w. treated diabetic group. After the treatment period (28 days), blood samples were collected for biochemical studies, and the pancreas was dissected for histopathological studies. The in vitro antidiabetic studies revealed the antidiabetic potential of bitter honey compared to standard acarbose. Treatment of diabetic rats with bitter honey revealed a statistically significant reduction (P<0.05) in the levels of fasting blood glucose (FBG) compared to untreated diabetic rats. This was accompanied by an elevated HDL and a decrease in LDL, VLDL, triglycerides, total cholesterol, SGOT, SGPT, urea, and creatinine. Histopathological changes in the pancreas indicated a marked improvement in a dose-dependent manner. The study concluded that bitter honey could potentially decrease the levels of FBG in diabetic rats and the various biochemical and histopathological abnormalities associated with diabetes mellitus.