This study evaluated the hypoglycaemic effects of fractionated neem leaf extract (IRC) on alloxan induced diabetic wistar rats. IRC dissolved in phosphate buffered saline (PBS) PH 7.2 was administered as 50 mg/kg, 500 mg/kg, 1000 mg/kg, 2000 mg/kg single doses and 5 mg/kg, 50 mg/kg, 250 mg/kg and 500 mg/kg repeated doses in the diabetic rats while in the normoglycaemic rats 100 mg/kg and 250 mg/kg were used respectively. The positive control groups received single and repeated doses of glibenclamide (5 mg/kg) while the negative control groups were left untreated in each case. Single doses of the extract in diabetic wistar rats produced maximal dose dependent percentage reduction after 4 hours of administration with percentage reductions of 13.10% (500 mg/kg), 14.40% (1000 mg/kg) and 17.50% (2000 mg/kg) respectively. The result shows that 500 mg/kg repeated doses gave the highest percentage reduction in fasting blood glucose in alloxan induced diabetic rats after 7, 14 and 21 days as follows 55%, 31.7% and 29.3% while 250 mg/kg repeated doses produced the highest percentage reduction of fasting blood glucose in non-diabetic rats at 7, 14 and 21 days and are 21.4%, 26.6%, 25.16% respectively. In conclusion, IRC lowered fasting blood glucose levels in non-diabetic and alloxan induced diabetic rats when given orally.