Merge pull request #699 from marionbarker/working-docs

Add Automated Dosing section to Closed Loop page

docs/operation/loop/close-loop.md

@@ -47,3 +47,24 @@ Start with meals that you know well. If Loop suggests less or more insulin than
 	* Loop will not automatically provide more insulin until your glucose is above the lower range of the correction range (but will recommend a manual bolus)
 
 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.
+
+## Automated Dosing
+
+Loop calculates a predicted glucose curve based on your programmed settings for carb ratio (CR) and insulin sensitivity factor (ISF), using your glucose, insulin and carb history. 
+
+If you enter a bolus without entering carbs, the prediction will be for your glucose to go low. (The Loop model calculates a negative number for recommended bolus.) For this case, Loop issues a Temp Basal to prevent the low, typically 0.0 U/hr but always less than your scheduled basal rate.
+
+!!! tip "COB and IOB"
+    * <code>COB</code> is the carbohydrates (g) that Loop expects to be absorbed
+    * <code>IOB</code> is the current active insulin (above or below the scheduled basal rate)
+
+If you enter carbs and select `Save without bolusing`, you have COB without associated IOB. In that case, Loop predicts your glucose will start rising and updates the recommended bolus, which includes consideration of your [`Glucose Safety Limit`](../../loop-3/therapy-settings.md#glucose-safety-limit), [`Correction Range`](../../loop-3/therapy-settings.md#correction-range) and [`Maximum Bolus`](../../loop-3/therapy-settings.md#maximum-bolus) . If that recommended bolus is positive, Loop might deliver some part of that bolus automatically - the exact percentage and timing of that delivery depends on your [`Dosing Strategy`](../../loop-3/settings.md#dosing-strategy). At each loop cycle (new glucose reading), Loop updates the prediction and calculates a new recommended bolus. When you enter carbs without bolusing, Loop may start delivering some insulin, but if your glucose doesn't start rising as Loop expects, it revises the recommended bolus.
+
+!!! tip "When does Loop start dosing?"
+    The glucose prediction is for the next 6 hours (the duration of insulin action), which is why the predicted glucose plot is included on the bolus screen. Loop considers glucose prediction with respect to your scheduled `Correction Range` over the full DIA, weighting closer predictions more than later predictions, when calculating [Recommended Bolus](../algorithm/bolus.md).
+
+    It is actually easier to answer when Loop will **not** automatically increase insulin delivery:
+
+    * If at any time in the next 3 hours, Loop predicts glucose below `Glucose Safety Limit`, Temp Basal is immediately set to 0.0 U/hr and recommended bolus is set 0 U
+    * If the eventual glucose (at the end of 6 hours) is greater than your `Correction Range` but the prediction dips below the low-end of your `Correction Range`, there is no automatic delivery
+        * The recommended bolus can be positive, which you see if you tap on bolus icon manually