Fasting blood sugar/ gestational diabetes

Hello momshies! Ano po best time mag fasting para sa FBS? Overnight ba or hapon? My OB suggested 6-8 hrs fasting. 3.30 pm na ako nakunan ng dugo. Result is my GESTATIONAL diabetes ako-96.Nag fasting lang ako ng 6 hrs. Parang balak kong ipa ulit... What do you think po?