Insulin Carbohydrate Ratio


  • ICR can be transferred from your pump

  • Adjust your ICR by performing a test meal experiment or observing autotune.

ICR refers to the amount of carbohydrates one unit of insulin is able to neutralize.

Example: Bill has a 1:10 ICR (aka an ICR of 10). If Bill has 20 carbs with lunch, he will need 2 U of rapid inslin to neutralize it.

ICR is not changed as drastically as basal rates or ISF unless Dynamic CR is enabled. As always, your ICR must be as accurate as possible for proper iAPS function.


It is safe to transfer your ICR from your pump settings. Your settings may not be accurate if you are experencing high peaks with meals, or if you have lows three hours thereafter. If you have SMB/UAM on and are experencing sharp drops, you additionally may need to optimize your ISF.

There are two suggested methods of optimizing your ICR. The standard way is a test meal experiment and can be done while not looping. Have meal with a known amount of carbohydrates and bolus according to your current ICR. Monitor your blood sugar at the three hour mark; did you go high, low, or end up where you started prior to the meal? If you ended up high, you can make your ICR more aggresive by 10%. If you were low, drop it by 20%. You may also look to increasing or decreasing your adjustment factor respectively, if you have dynamic CR on.

If you have autotune enabled, you can monitor the general trend in ICR adjustment. When the autotune value stabilizes, you can go ahead and change your scheduled value to the autotune value, allowing the system to continue making changes if it were being limited by a safety limiter.