Insulin Calculating

“Errors in calculation of insulin dosageby adolescents occur frequently,” writeU.C. Davis researchers in a recent study.“Consistent use of an insulin dosagecalculation device may help to improvemetabolic control in adolescents usingmultiple daily injections (MDI) orcontinuous subcutaneous insulin infusionpumps (CSII).”

The researchers evaluated the impact of aninsulin dosage calculation device (IDC) onmetabolic control, treatment satisfaction,regimen adherence and quality of life inadolescents using MDI or an insulin pump.

The IDC was used in 83 adolescents.

Patients received training on dosagecalculation using either the IDC orconventional methods, and they performedsample calculations.

“We observed a higher frequency oferrors with conventional calculationsthan with the IDC,” write the researchers.“At six months, there was a trend towardimproved A1C in the IDC group overall anda significant improvement in the subsetwho used the IDC consistently.”

Journal of Pediatric Endocrinologyand Metabolism, December 2004

Nicole Glaser, MD, is an assistant professor of pediatrics at theUniversity of California, Davis School of Medicine and was a leadresearcher for the study.

Why is this study important to type 1 kidsand their parents?

Many adolescents are responsible for their owndiabetes care. Often, they find dosage calculations tobe time-consuming and cumbersome, and sometimesthey resort to estimating dosages rather thancalculating them precisely. This study confirms thaterrors in calculating insulin dosages occur frequentlyin adolescents using MDI or CSII, and that a simple,inexpensive device can help to improve control, likely bydecreasing dosage errors. Although more recent modelsof insulin pumps have bolus calculation “wizards” builtinto the software, this is not available to patients whouse MDI, making the devices perhaps most useful forthose patients.

What is an IDC, and can it be used in a clinical setting?

The IDC is a simple, inexpensive device that calculatesinsulin dosages by combining the patient’s insulin tocarbohydrate ratio with the correction scale for bloodglucose. The device is circular and made of two layersof laminated cardboard. To use it, the patient turns theupper disc in relation to the lower disc, and the correctinsulin dosage appears in a clear window.

All of our patients use the IDC at home. We give it tothem at the clinic, and then we explain how it is usedat the clinic session (usually with a teaching sessionon carbohydrate counting). They then carry it withthem, usually in their glucose meter case, and use it tocalculate dosages for all meals.

The devices will be called “InsuCalc” and should beavailable by summer of 2005. They can easily be used inany clinical setting (adult as well as pediatric), and areideally given to patients by a physician, CDE or dietitian.Learning to use the device requires about three to fiveminutes of instruction.

More information about the InsuCalc will be availablesoon at, and healthcare providers will be able to place orders directly from the site.

Can you speculate why you observed a higherfrequency of errors with conventional calculationsthan with the IDC?

There are so many steps to the calculations that Ithink it is easy to make errors. After determining thecarbohydrate content of the meal, patients have tomultiply by the ratio of insulin to carbohydrate, thenadd units according to the correction scale. Some ratiosof insulin to carbs are very easy to use, such as 1 unitfor every 10 grams, but others involve more difficultcalculations, such as 1 unit per 7.5 grams. In our study,we asked the teens to calculate the dosages usingwhatever means they normally would use, and sincemost don’t use electronic calculators, many mademistakes.

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