Variability Index (Average Daily Risk Range, ADRR)
This measures how much your BG swings from low to high and vice versa. Variable BG is a problem for three reasons. First, the more your BG changes, typically the worse you feel. Our research shows that greater BG variability is associated with feeling more depressed. Second, the more your BG varies, the more likely you are to slip down into hypoglycemia. Third, variable BG may contribute to the development of certain diabetic complications-as much or more than elevated HbA1c does.
Look at the graphs in Illustration 1 below. The first graph, of Person A, shows a very high Variability Index. The second graph, of Person B, shows a very low Variability Index. Both Person A and Person B have the same HbA1c. The Variability Index gives you more information about how widely your blood sugar swings between highs and lows.
As you can see in Illustration 2, if your BG Variability Index is below 20 that means your BG is not changing much and is at Low Risk for extreme glucose excursions (i.e. BG below 40 mg/dl and/or above 400 mg/dl). If your BG Variability Index is 20-39, you are at Medium Risk for extreme glucose excursions. High Risk is Variability Index greater than 40, which means you should talk to your health care provider about controlling glucose variability. (The red and green pointers illustrate BG variability for Person A and Person B of Illustration 1)
While some peoples' BG generally changes more than others', variable BG can be due to many overtreatment reasons such as taking too much insulin, exercising too much, cutting back too much on carbohydrates when your BG goes high, or eating too many carbohydrates when your BG is low.
Like the HbA1c, the Variability Index changes slowly and updates once a week, so don't expect to see it change after working hard for a few days to curb swings.
Kovatchev BP, Otto E, Cox DJ, Gonder-Frederick LA, Clarke WL (2006). Evaluation of a New Measure of Blood Glucose Variability in Diabetes. Diabetes Care, 29: 2433-2438. Free full text available in HTML and PDF formats.
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