Background: Diabetes Mellitus (DM) is a major health issue worldwide, with hyperglycemia being the primary symptom. Uncontrolled hyperglycemia in diabetes mellitus can lead to a variety of complications. This research aims to analyze the effectiveness of black garlic in reducing blood glucose in diabetic rats induced by streptozotocin. Methods: A randomized pretest-posttest-only control group design was used in this experimental study. Twenty-four male Wistar Rats were divided into six groups randomly, that is a normal group (N) without any treatment, a negative control group (C-) with streptozotocin induction, a positive control group (C+) with streptozotocin induction plus administration of metformin 45mg/kg BW and treatment groups (T1, T2, and T3) with streptozotocin induction plus administration of black garlic at doses of 72 mg/200gBW/day, 144 mg/200gBW/day, and 288 mg/200gBW/day respectively. The study was conducted for 14 days of treatment. Blood glucose was measured with a glucometer, and statistical analysis was performed using SPSS 26 by paired t-test. Results: Based on the Comparability analysis, giving black garlic for 14 days showed significant differences in blood glucose levels before and after treatment in groups C-, C+, T1, T2, and T3 with P<0,05. Based on the different averages of the data, in group C+, there was a significant increase in blood glucose levels, while in groups C-, T1, T2, and T3, there was a significant decrease in blood glucose levels. Conclusion: Black garlic significantly lowers blood glucose levels in white male rats (Rattus norvegicus) diabetes mellitus model induced by streptozotocin.