The aim of the present study was conducted to assess the correlation and the influence of the coexistence of diabetes,, thyroid, leptinand biochemical variables related to carbohydrate and lipid metabolism in patients suffered from either type 1 diabetes ( T1DM; 1DDM) or type 2 diabetes (T2DM;NIDDM). The study was performed on 100 individual collected from the outpatient and inpatient clinics of diabetes. They divided into 5 groups as follow; volunteer apparently healthy, IDDM with complications and NIDDM without complications. The obtain results revealed an increase in the level of glycosylated haemoglobin (HBA1C) in individuals with higher levels of blood glucose, hypercholesterolemia and hypertriglyceridemia in diabetic patients with more increase in patients suffered from IDDM with complications. Patients suffered NIDDM with complications show higher level of leptin than other groups. There is an increase in serum TSH level in patients suffered from IDDM with complications than other groups with reduction in T3 and T4 levels. On the other hand, there is a decrease in serum TSH level in patients suffered from NIDDM with complications than other groups with elevation in T3 and T4 levels. In conclusion, the present study indicates a significant negative correlation between serum T4 and leptin in NIDDM with complications. A negative correlation is showed between serum T3, T4 and leptin in IDDM with complications.