Abstract: Phytochemistry of Momordica charantia L. leaves revealed the presence of flavonoids and tannins. The hypoglycaemic effect of M. charantia leaves as well as the plant`s effect on rats` weight under different treatment patterns was assessed. Forty wistar rats weighing between 140-250 g were categorized into eight experimental groups of five wistar rats per group. The efficacy of 250 mg kg-1 methanolic extract of the leaves on alloxan-induced diabetic rats showed mild hypoglycaemic effect within 24 h. There was no evidence to establish that parenteral route is more efficacious than the oral route of administration of the treatment plant. The experimental rats that was alloxan-treated to induce hyperglycaemia and treated with 500 mg kg-1 of methanolic extract of the treatment plant as well as those induced with alloxan without treatment with methanolic extract of M. charantia showed significant loss in weight (p < 0.05) after twelve weeks. The controls as well as those treated exclusively with methanolic extract of treatment plant without alloxan treatment had significant weight gain (p < 0.05). The results generally indicate that methanolic extract of the leaves of M. charantia has hypoglycaemic potential especially on long-term use.