Step 10: Test Settings

Time Estimate

  • 2 hours to read the the rest of LoopDocs (particularly "Set up App", "Operate", and "FAQ" sections) and LoopTips thoroughly and thoughtfully
  • 15 minutes to take this quiz to make sure you've familiarized yourself with Loop's expected behavior
  • 1-3 days to test settings if you are a normal person who wants to get the most out of Loop


  • A small amount of effort to test/validate basals, carb ratios, and ISF (correction factor) will eliminate a lot of uncertainty when you start Looping.
  • Keep an open mind that settings may need to change just as you start Loop. Hormones, illness, and failed sites can still happen just like always.


  • "My endo makes my pump settings, so do I really need to test them?" Well, nobody is going to force you...but testing your settings even just a couple days will give you a tremendous advantage going into Loop. Your endo may have very conservative overnight ISF and carb ratios that normally don't get used in traditional pump therapy, but will be used by Loop for sure. So, keep an open mind as you head into Looping on old settings if you haven't tested them recently.
  • "I have great control, why would I need to test my settings?" Awesome for you! However, it is quite possible that your "great control" comes with a lot of little adjustments all the time. We all got used to needing little bumps and nudges of insulin or carbs over time...and sometimes those bumps and nudges are covering for underlying settings that need adjustment. Testing your settings will help...especially if you are coming from a treatment style that involves memorizing your insulin doses for may not know your actual carb ratio or ISF as a result of "just knowing" your boluses.
  • "I can't basal test with my 2-year-old. What can I do?" I agree, that would be pretty tough. Consult your endo, watch your patterns, and do the best you can...little kiddos are a difficult group to do settings testing with. I feel ya.

Loop is just a fancy calculator underneath the hood. The math problems that it is solving depend on some settings that you will be providing it. It's a good idea to make sure you do a bit of settings testing before using Loop.

Basal rates, if properly set, will keep your blood glucose steady without food present. You can test your basals by having a relaxing set of 4-6 hours without eating at least two hours before you begin the test. Does your blood sugar stay steady? Or do you climb and need a correction? Or do you go low and need to eat? Setting basals is a HUGE important step to setting yourself up for Loop success.

Insulin Sensitivity Factor (sometimes called Correction Factor) is how much one unit of insulin will bring down your blood sugar. The higher the value of this setting, the more sensitive to insulin you are. An ISF of 30 means one unit of insulin brings your blood sugar down 30 mg/dL. You can test this setting after you get good basals set and tested. Simply bring yourself to a higher BG with a glucose tab or other small quick carbs. Wait until you see yourself plateau again at the higher BG, then make a correction. Wait 4-6 hours (again no food) and see where your correction lands your blood sugar. Divide the BG drop by the amount of correction insulin you delivered...that’s your ISF.

Carb Ratio is the amount of carbs covered by one unit of insulin. Ideally a good carb ratio will bring your BG back to starting point within 2-3 hours of the meal. (High fat/protein meals may cause BGs to be impacted longer.) If you are spiking higher than you’d like after a meal but still coming back to starting BG, consider prebolusing your meal by 15-20 minutes rather than changing carb ratio.

Check for a discussion on how to check all these settings and why they are important. If you’re fascinated by this topic, read the book Think Like A Pancreas for a really great discussion. Finally remember settings can change periodically. Hormone cycles, steroids, illness, etc may lead to a need to change settings.

Next Step: Make Plans for Loop Data

Now you are ready to move onto Step 11 to Make Plans for Loop Data.