Adjusting Settings for Loop

Loop is an incredible tool for managing Type 1, but at least for now, it doesn’t learn on its own. It’s incredibly dependent on you providing the proper values for basal schedule, ISF, and carb ratio in particular. Katie’s post on fine-tuning settings is the authoritative post on this topic. This post has less info in terms of the why, and is a bit more prescriptive about exactly how to do the testing.

For all testing, there are a few prerequisites. Some of these are a MUST and others more of a SHOULD:

• CGM sensor should be between 2 and 12 days old
• Pump site should be at least 6 hours old, and should not be replaced during the test
• No significant lows leading up to the test
• No significant exercise during the test
• Do not disconnect or suspend the pump during the test
• Make notes in Nightscout

Basal Testing

The first and most important settings to get right are the basal settings. Loop assumes that your basal schedule would keep you steady barring other factors, so if that’s not the case, everything else will be thrown off. The challenge with basal testing, particularly with young kids, is that you have to fast to get the best results. We’ve found breaking the day into four parts works well enough, but if you can fast a little longer, it’s certainly easier to do two or three longer tests.

Test 1 (12:00 AM – 6:00 AM Basal):

• 6:00 PM – Last meal and bolus. No additional food or boluses or test should be cancelled.
• 10:00 PM – BG should be between 80 and 140 and relatively stable
• 11:00 PM – Open Loop
• 12:00-8:00 AM – No food or boluses unless BG is above 200 or below 70 (if so, cancel test)
• 8:00 AM – Bolus for breakfast, close loop

Test 2 (6:00 AM – 12:00 PM Basal):

• 12:00 AM – Last meal and bolus. No additional food or boluses or test should be cancelled
• 4:00 AM – BG should be between 80 and 140 and relatively stable
• 5:00 AM – Open Loop
• 6:00 AM-12:00 PM – No food or boluses unless BG is above 200 or below 70 (if so, cancel test)
• 12:00 PM – Bolus for lunch, close loop

Test 3 (12:00 PM – 6:00 PM Basal):

• 7:00 AM – Last meal and bolus. No additional food or boluses or test should be cancelled
• 10:00 AM – BG should be between 80 and 140 and relatively stable
• 11:00 AM – Open Loop
• 12:00 PM-6:00 PM – No food or boluses unless BG is above 200 or below 70 (if so, cancel test)
• 6:00 PM – Bolus for dinner, close loop

Test 3 – easier option (12:00 PM – 6:00 PM Basal):

• 8:00 AM – Last meal and bolus. No additional food or boluses or test should be cancelled
• 10:00 AM – BG should be between 80 and 140 and relatively stable
• 10:00 AM – Zero carb snack
• 11:00 AM – Open Loop
• 12:00 PM-6:00 PM – No food or boluses unless BG is above 200 or below 70 (if so, cancel test)
• 3:00 PM – Zero carb snack
• 6:00 PM – Bolus for dinner, close loop

Test 4 (6:00 PM – 12:00 AM Basal):

• 1:00 PM – Last meal and bolus. No additional food or boluses or test should be cancelled
• 4:00 PM – BG should be between 80 and 140 and relatively stable
• 5:00 PM – Open Loop
• 6:00 PM-12:00 AM – No food or boluses unless BG is above 200 or below 70 (if so, cancel test)
• 12:00 AM – Close loop

Test 4 – easier option (6:00 PM – 12:00 AM Basal):

• 1:00 PM – Last meal and bolus. No additional food or boluses or test should be cancelled
• 4:00 PM – BG should be between 80 and 140 and relatively stable
• 5:00 PM – Open Loop
• 5:00 PM – Zero carb dinner
• 6:00 PM-12:00 AM – No food or boluses unless BG is above 200 or below 70 (if so, cancel test)
• 12:00 AM – Close loop