Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both .The aim of this study was to find the correlation between HbA1c with FBS and establish a conversion equation between them, and also to examine the relationship between glycohemoglobin (HbA1c) and age and gender difference as well. Finally, try to set up diagnostic criteria related to early diabetes and to detect pre-diabetes. This was a cross-sectional study done in diabetic hospital, Tripoli. There were 100 cases enrolled during period study. All fasting blood sugar (FBS) and HbA1c data of each case were collected for study .The study target is to prove if we can rely on HbA1c values to assess the diabetic complication and consequently used it as to assess their usefulness in monitoring the glycemic control in diabetic patient and predictive biomarker to prevent the diabetic complications.