The analysis of M. charantia leaves collected from Benin city, Edo, Nigeria, revealed the presence of flavonoids and tannins. The hypoglycaemic activity of the methanolic extract (ME) of M. charantia leaves in rat was evaluated. Forty Wistar rats weighing 140-250 g were categorized into 8 experimental groups of 5 Wistar rats per group. The efficacy of 250 mg ME kg^-1 in alloxan-induced diabetic rats showed mild hypoglycaemic effect within 24 h. There was no evidence to establish that parenteral route is more effective than the oral route of administration of ME. The experimental rats that was alloxan-treated to induce hyperglycaemia and treated with 0 or 500 mg ME kg^-1 showed significant loss in weight (p<0.05) after 12 weeks. The controls and those treated exclusively with ME without alloxan treatment had significant weight gain (p<0.05). The results generally indicated that ME has hypoglycaemic potential especially on long-term use.