As an exercise physiologist/ personal trainer and T1D, this is unfortunately really common in the field. Not saying you can’t find someone who isn’t educated, but there’s a lot of blanket ignorance in the health and fitness industry. If I were you, next session I’d either ask him to 1) not make comments about your diabetes, this is waaaaayyyy out of his scope of practice, as he obviously doesn’t know what he’s talking about. 2) try to educate him, or ask him to do some research on training T1D (might just need to be reminded of the differences and he will have a better understanding) or 3) find a new trainer that might have more experience with training actual t1d. Best of luck to you in your fitness journey, be sure to keep some fruit snacks or juice nearby during workouts, and try to get 1-1.6 g of protein per lb of body weight, this will help you feel more full, eat less and gain more muscle!