Background: Fibroblast growth factor 21 (FGF21 regulates several biochemical pathways such as glucose/fructose update, lipid oxidation, and insulin/glycogen sensitivity. Some beneficial effects of FGF21 on human body have been investigated, including weight loss and improved glycemia. It has been also suggested as a therapeutic agent for Diabetes Type 2. Aim : Τhe aim of this study is to measure FGF21 serum levels in diabetes mellitus patients, compare them with FGF21 levels in healthy individuals and correlate them with age, carbohydrate and lipid metabolism markers. Methodology : In this study. FGF21 levels in 35 diabetics and 23 non-diabetics were correlated with Glucose, HBA1c, Cholesterol, Triglycerides, HDL-cholesterol, LDL-cholesterol concentrations. Results : FGF21 concentration is doubled in diabetics. (both men and women). independently from the patients' age. and it was statistically significant. No statistical correlation between FGF21 and other biochemical markers in diabetic and non-diabetic individuals. as well as within the two subgroups of participants aged <40 years old. and > 40 years old was recorded. Conclusion : FGF21 is an important metabolic regulator, which its concentration was found increased in diabetics serum, in the present study, while no statistical correlation was found between FGF21, age of the participants and other biochemical markers.