Diabetes is one of the leading causes of death and has become an alarming disease with its increasing prevalence rate. Through the times, humankind has been into various medical discoveries for the treatment of various diseases. And thus, plants had been widely the focus of study as sources of treatments. The study was conducted to determine the blood glucose lowering activity of the Lumboy (Syzygium cumini) leaf crude extract in hyperglycemic rats induced with Medic orange. The leaf extract was also tested for its toxicity and determination of approximate effective dose and effective dose at 50% of the test animal population. Findings revealed that the Acute Oral Toxicity Test found Lumboy leaf extract as a nontoxic substance. Approximate Effective Dose was determined at 10 mg/kg to 2511.9 mg/kg while Effective dose of population was at <39.81 mg/kg. The leaf extract was then used for the formulation of solution and bioassay result showed no significant difference between the blood glucose lowering activity of the Lumboy leaf extract and Metformin solution using albino rats.