When you feel like you have learned what you need from open-loop, you should be ready to switch to close-loop. There are several ways you can help make that transition as smooth as possible.
Many people choose to transition to close-loop in a step-wise fashion. Starting close-loop on weekends is an easier starting point so that you can minimize distractions (let's face it...you'll probably be staring at the Loop a lot for those first few days). Typically, people have an easier time transitioning to close-loop for parts of their day that don't involve food...so nighttimes tend to be easier than daytimes to start.
Maximum Basal Rate⌁
When you are first beginning to close-loop, it is important to be conservative (low) in setting your maximum basal rate. If your settings are incorrect in other areas (basal rates, carb absorption time, carb ratio, etc), Loop may enact incorrectly aggressive high temp basals. Gradually increase your maximum basal rate as your comfort and confidence in Loop increase. Typically, experienced closed loop users set their max basal rate no more than 3-4 times their average basal rate.
If your basals, ISF, or carb ratios aren't set correctly, Loop may overshoot and leave you lower than expected (or with more IOB than you are comfortable with). Setting your low BG target slightly higher can help prevent unexpected lows or high IOB as you adjust your settings.
Watch the IOB⌁
Watch whether Loop accumulates positive or negative IOB while holding your BG steady when no food is present. If you find that you are "carrying" positive or negative IOB consistently, you should review your settings to see if perhaps your basal or ISF needs adjusting.
Meals will likely be the hardest part of transitioning to close-loop. Starting with foods that you have a high comfort level with is a great idea. If you have favorite meals that you know well (how high BGs usually go, how much to bolus, how to pre-bolus, etc), these would be a good starting point. Watching when the Loop high temps or suspends basals (early vs late in the meal) will really help you adjust to find your typical carb absorption times. As a general idea, assuming other settings are accurate:
- early high temps in a meal that leave you low after, you may need to shorten carb absorption time
- early suspensions in a meal that leave you high after, you may need to lengthen carb absorption time
This is definitely an area where YDMV (your diabetes may vary), so don't expect or accept that what works for others will work for you. Test, observe, and adjust as needed.