Before I started to use DIY Loop, I was eating low-carb meals (< 30 grams/day) twice per day. I took two boluses for each meal. The first one was calculated using the carb content of the meal in the usual manner: carbs/insulin-to-carb ratio and given at least 15 minutes before eating.
I also took a separate dose to cover fat and protein. I counted up 50% of the protein grams and added it to 10% of the fat grams and thought of that total as carbohydrate equivalents.
Once I knew the carb-equivalents for the protein and fat, I decided by the insulin-to-carb ratio and found the total insulin needed for protein and fat. I delivered that bolus in an extended fashion so that I never exceeded 1.2 insulin units/hour. I delivered the protein/fat extended bolus right after the immediate carb bolus.
For example, if my meal was comprised of 10 grams of carbs, 60 grams of protein and 60 grams of fat, using an insulin to carb ratio (I:C) of 1:10, here’s how I figured my dosing. Immediate carb dose: 10 carbs/10 (I:C) = 1 unit of insulin.
For the extended bolus to cover protein and fat, here’s the arithmetic I used. Protein 60 grams x 50% = 30 carb equivalent grams. Fat grams 60 x 10% = 6 carb equivalent grams. Total carb equivalents grams = 30 + 6 = 36.
Divide 36 carb equivalents by 10 (I:C) = 3.6 units. Since I want to limit my extended bolus to a maximum of 1.2 units/hour, I will deliver these 3.6 units at 1.2 units/hour for 3 hours. Typical extended boluses ranged from 2-6 hour duration.
I found this system to be dependably repeatable and enjoyed excellent glucose control, especially 3-6 hours after the meal.
Is there any way that you might be able to switch your one meal to earlier in the day? Eating close to bed-time (< 3 hours from last bite to head hitting the pillow) increases the risk of poor post-meal control and it sabotages your ability to sleep well.