Background: Studies on the determination of carnitine levels and nutritional status in patients of type II diabetes. Objective: We designed this study to determine changes of serum-free L-carnitine in type II diabetic women. Design: A cross-sectional study (case-control study). Setting: Clinical of Endocrinology and Metabolism, Sina Hospital, Pharmacological Research Center, Tabriz Medical university, Iran. Patients and methods: Taking into account the importance of the control of diabetes, in the present case-control study, the levels of serum-free L-carnitine, blood glucose and lipids, systolic and diastolic blood pressure, body mass index (BMI) and nutritional status assessed in the case and control groups which were selected by the simple sampling method. The control group (n ¼ 18) included patients with no complications and the case group (n ¼ 33) was grouped into three subgroups including patients with retinopathy, hyperlipidemia and neuropathy. Results: Study results indicated that the mean serum-free L-carnitine concentration in the case group was significantly lower than its mean concentration level in the control group, 39.6378.99 vs 53.4270.93 mmol/l, respectively (Po0.001). Serum-free L-carnitine in retinopathy, hyperlipidemia and neuropathy case subgroups were 39.0379.89, 39.6378.99 and 40.44712.50 mmol/l, respectively (P40.05). No significant difference was found between the serum-free carnitine levels of the case subgroups. The mean blood glucose, triglycerides, total cholesterol, low-density lipoprotein cholesterol, very lowdensity lipoprotein cholesterol levels and systolic and diastolic blood pressure were significantly higher in the case group than in the control group. Conclusion: In this study, the mean serum-free L-carnitine levels in diabetic patients with complications was almost 25% lower than in diabetic patients with no complications. On the basis of the study results, carnitine supplementation in diabetic patients, especially in patients with diabetes complications, might be useful.