The present study was conducted to assess the interrelationship and the influence of the coexistence of diabetes,  leptin, thyroid  and biochemical variables related to carbohydrate and lipid metabolism in patients suffered from either Type 1 diabetes (T1DM; IDDM) or Type 2 diabetes (T2DM; NIDDM). The study was performed on 100 individuals collected from the outpatient and inpatient clinics of diabetes. They divided into 5 groups as follow; volunteer apparently healthy, IDDM with complications, IDDM without complications, NIDDM with complications and NIDDM without complications. The obtained results revealed an increase in the level of glycosylated hemoglobin (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 from 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 TSH and leptin.  A positive correlation is found between serum T4 and leptin in NIDDM with complications. A negative correlation is showed between serum T3, T4 and leptin in IDDM with complications. Additionally, there is a significant positive correlation between serum leptin and cholesterol, also between serum leptin and triglycerides in IDDM with complications.