So let me know if I get this straight. You already had been to the residence earlier that night (an hour and a half earlier as you had stated) and had you obtained your SAMPLE history, you would have realized that he was a diabetic and realized that chances were his condition was probably associated with this even though he was A and O x 4/4. Is this something that you did? I know that with myself, my level can go below 2 mmoL (normal range is between 4 - 8) and I am still A and O x 4/4, and I present with a slight headache.
Now, with this being said, you could have taken his BGL (blood glucose level) on the first call and seen if this was within his normal range and find out what meds he was on and the last time he had eaten. This would have helped you immensely on your second call with him. If you would have taken his BGL on the first call and realized that it was below his normal range, then you could have given him the oral glucose. Here, the EMT use D50W and can also hang a line of D5W to help prevent his sugar levels from spiking then falling below his normal range again.