This study aimed to see how allicin (45mg/kg BW) affected diabetic Mellitus in male rats (DM). Forty male rats were utilized, and they were split into four groups at random for 42 days. T2 was treated with 45 mg/kg B.W of allicin dissolved in 1 ml of D.W daily and injected with a single dose of sodium citrate buffer (0.5ml Intra-Peritoneal IP), DM was induced in T1 and T2 by injection of a single dose of streptozotocin 50 mg/kg B.W IP, T1 was assigned as a positive control, T3 received 45 mg/kg B.W. of allicin dissolved in 1 ml D.W. every day, and a single dose of sodium citrate buffer was injected (0.5ml IP). When diabetic rats treated with allicin in T2 were compared to diabetic rats in T1, the findings indicated a significant increase (P0.05) in body weight growth, insulin, total protein, and albumin, better lipid profile, and reduced glucose concentration. Histological investigations revealed that the island of Langerhans had atrophy and necrosis in the exocrine tissue in the T1 group, whereas the T2 group had a large island of Langerhans. The findings in the T3 group marked hyperplasia of the island of Langerhans. The 45mg/kg, B.W. of allicin, has a hypoglycemic effect and elevates the expression level of insulin and pancreas tissue protection effect when used orally in adult rats at the given dose for forty-two days.