My dad's hba1c is below normal but fasting sugar checked today came as 7.83. what does this means? really worried.

Fasting gluc. vs. A1: Hi. A1c is less sensitive for diagnosis than fasting glucose. And I doubt your dad's A1c is below the normal range; more likely it's somewhere near the upper end of the normal range (at least) if his fasting glucose is 7.83. He should see his doctor for formal testing and appropriate management. Healthy diet and regular exercise are mainstays. Good luck!