Abstract: Diabetes mellitus is known as a metabolic disease characterized by hyperglycemia caused by impaired insulin secretion, insulin action, or both and impaired metabolism of carbohydrates, fats and proteins. Diabetic angiopathy is a chronic complication of diabetes mellitus occurs in essential blood vessels throughout the body, started by endothelial dysfunction of vascular endothelial. Chitosan increases cardiac performance due to amino polysaccharide molecules. This study aims to determine the use of chitosan as adjunctive therapy for diabetes mellitus by looking at the arterial lumen of the heart arteries . Histopathological changes were observed by seeing the blood that filled the lumen of the heart arteries. Sixteen white rats divided into two groups: group 1 as treatment groups were injected by streptozotocin and group 2 as a treatment group was injected streptozotocin and giving chitosan. Data collection of coronary arteries was performed with a score of 3 >75 %, between 25%-75% given two scores, and < 25% were given rating 1. The results of paired t-test can be significant value between the observation of the blood that filled the lumen of the blood vessel of the heart (p:<0,005) indicating there is a significant difference between diabetic rats with streptozotocin that given chitosan compare with diabetic rats were not given chitosan. It can be concluded that chitosan as adjunctive therapy for diabetes mellitus can improve the lumen of the heart arteries.