What is the ruling on a voluntary fast for someone who intended to fast, then experienced a drop in blood sugar two minutes before the Fajr adhan, and consequently ate?

The crucial point for a fasting person to abstain from eating is the advent of dawn (Fajr). If the muezzin calls the adhan at the break of dawn, then there is no harm in eating two minutes before his adhan. What people circulate about the obligation to stop eating ten or fifteen minutes before Fajr is not prescribed (in religious law) and is not binding. However, if one eats after the advent of dawn, the fast is invalid. The general principle is that the muezzin is trustworthy and knowledgeable of the times, and he calls the adhan at its proper time. The prayer times are generally based on their accurate correspondence with the actual time.