Talk to Diabetologist on High Fasting Blood Sugar Levels

My father has been a diabetic patient for more than 30 years. He's taking insulin for more than 20 years but the fasting sugar levels are coming too high. Random levels are fine. Recently I found this Nutrifactor Glucofactor food supplement for diabetes patients and I wanted to ask if my father can take this as a food supplement without hesitation? He can't intake glucerna or Ensure they instantly upset his stomach and causes loose motions.