Good luck with your op.
I was in hospital for 4 days and nights over last weekend.
Breakfast was the same every day. Porridge or weetabix or cornflakes (all with skimmed milk) or a soft roll with jam and a spread. Small tub of concentrated orange juice.
Lunch and dinner had a choice of 4 mains. 2 of them extremely carb heavy. (pastry, pasta, rice, potatoes) One was a sandwich with various thinly spread fillings and a "margarine" spread. The fourth was a salad, but the salad was always Cos lettuce with half a hard tomato cut in half, half an egg, coleslaw and a slice of cucumber. The protein varied between ham or a PORK PIE, or roast beef. No dressings, never any cheese. Puddings were an ice cream made from buttermilk (ingredients listed in order, water, sugar, buttermilk extracts, chemicals.), or a zero fat fruit yogurt, or a piece of fresh fruit, or rice pudding.
Teas and coffee were served with skimmed milk. One thing for sure, they were pushing carbs and insistent on as near zero fat as possible.
Mr Blue brought me some food in, which I was able to keep in the fridge, but he couldn't bring in enough for each meal.
In the end I gave up and ate the sandwiches.
They were taking my BG at random times during the day and nothing above 6.3. I was also checking myself, and they were OK.