On two different days you eat the exact same dinner, take the same insulin dose and have the same blood glucose level at the start of the meals, yet one evening when you check your glucose value two hours after dinner it is 100, and the next time it is 250.


What is going on?

No matter how hard you work to stay on track, you still experience the frustration of very high or low blood glucose levels. Getting it right is a constant balancing act.

Knowing where blood glucose is heading at the time of a meal is the key to preventing these variable glucose levels, says Lori Laffel, M.D., M.P.H., Chief, Pediatric, Adolescent and Young Adult Section at Joslin Diabetes Center.

In December 2016, the FDA approved the Dexcom G5 continuous glucose monitor (CGM) for non-adjunctive use. This meant that for the first time people on insulin therapy could use the data from the device to dose insulin.

In addition to real-time glucose values, however, the Dexcom G5 displays trend arrows that predict where your glucose level will likely be in the next 30 minutes. For example, double arrows up or double arrows down mean that over the next hour your glucose value may be more than 100 points higher or lower than it is at that moment.

Taking advantage of this function, Dr. Laffel and a panel of experts developed a set of guidelines specifically to help people with diabetes on insulin therapy improve overall glycemic levels. The guidelines are published in the Journal of the Endocrine Society (November, 2017).

The researchers created an easy-to-use table that allows Dexcom G5 users to make more accurate dosage adjustments at the start of a meal. While this approach still takes into account how many carbohydrates you plan to eat and your glucose level, what makes it different is that it also factors in the direction your glucose is going. Depending on whether your glucose is trending upward or downward, a unit or two of insulin, for example, will be added or taken away from the premeal insulin dose.

The recommended dose changes are based on a person’s insulin sensitivity. The amount of insulin needed to bring blood glucose down varies by each person’s correction factor or sensitivity index. The result is a more customized method so important in the management of diabetes.

“We are hoping that this is approach will be a starting point upon which people can improve their overall glucose levels, reduce glucose variation, and decrease the frustration that they experience when they see a lot of variability in their glucose readings after eating,” says Dr. Laffel.

It is a game-changer because previously we didn’t have the opportunity to take into account the directionality of glucose as the meal was beginning.


Lori Laffel, M.D., M.P.H.,
Chief, Pediatric, Adolescent and Young Adult Section

The approach is similar in children and adults. The guidelines include specific recommendations for children, adolescents, people of different sizes and ages, and those with different insulin sensitivities.

However, the tables were developed specifically for the Dexcom G5 device. “We have to be cautious because there are currently three CGM devices and the arrows might not mean the same thing on each device, so patients using other devices should speak with their providers in order to understand the meaning of the arrows,” Dr. Laffel says.

What is next? Education of healthcare providers so that this new method can be used practically by patients.

“We’re optimistic that this approach can be an easy approach to improve overall glycemic control, and at the same time take away some of the frustration of diabetes,” Dr. Laffel says.

Although this content is reviewed by Joslin Diabetes Center healthcare professionals, it is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition.