Aim: This study is aimed to determine the efficacy of HbA1c as a predictor in early diagnosis of GDM. Methods: A Prospective observational study was conducted at Geetanjali Medical College and Hospital, Udaipur from January 2020 to June 2021 in 106 pregnant patients with high risk factor for GDM attending antenatal OPD in the first trimester. Fasting blood glucose, HbA1c and all routine investigation at first trimester were performed. Patients with FBS >92 mg/dl or HbA1c was <6.5% in the first trimester were further evaluated in the second trimester for repeat HbA1c and 75gm 2hr DIPSI. In patients with HbA1c <6.5% and DIPSI value between 140-200 mg/dl were further subjected to 75 gm oral glucose tolerance test to confirm the diagnosis of GDM using WHO-2013 criteria.