Diabetic hypoglycemia. Course of action.

At 1:30 PM (before eating lunch) he started sweating and he felt cold to the touch so when I checked his Blood Sugar level with a machine it turned out to be 76. I checked again after 2 minutes and it was 55. So we gave him Glucon D and he ate lunch and then he seemed to be normal again. He had a healthy breakfast with roti, eggs, and milk about 5 hours earlier. He says that he had a similar episode a week ago. He had a bone fracture surgery a month ago. His medications are Telma-AM for hypertension, and Gluconorm -VG2 for mild diabetes. And after the operation he was given supplements/multivitamin with Vitamin D, Zinc, Calcium, magnesium. And also a tablet with Cissus Quadrangularis Extract. Please suggest the reason for this and future course of action.