Alternate-Site Testing

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Blood glucose self-monitoring using a blood sample from somewhere other than the fingertips, namely the palm, upper arm, forearm, abdomen, calf, or thigh.

The fingertips have traditionally been used for blood glucose self-monitoring because they’re rife with capillaries, and it is relatively easy to obtain a large enough drop of blood for accurate readings. However, the fingertips are also full of nerve endings and are very sensitive to pain. Many people would welcome a break from fingersticks, especially people who use their fingers a great deal, such as musicians or people who spend a lot of time at a computer keyboard.

Alternate-site testing is possible only with certain newer blood glucose meters that require a smaller drop of blood to produce accurate blood glucose readings and have been approved by the U.S. Food and Drug Administration for this purpose. Each meter’s user manual specifies what parts of the body can be used to obtain the blood sample.

In the past few years, a number of studies have been performed to compare the accuracy of alternate-site testing results with results from fingertip blood glucose monitoring. The studies have generally shown that during “routine” blood glucose monitoring, such as before meals (when fasting) or two hours or more after meals or exercise, the results from alternate sites correspond well with results from fingertip monitoring. However, because glucose utilization in the fingertips is faster than in the arms or other sites, when blood glucose level is falling rapidly (for example, immediately after exercise) or rising rapidly (during the first hour after a meal, say), alternate-site readings lag behind fingertip readings. This could result in delayed detection of hypoglycemia or sharp changes in blood glucose level. Therefore, alternate-site testing should not be performed directly after a meal or exercise or when you think your blood glucose level is low or falling. It is also recommended that you confirm alternate-site low readings with a fingerstick check before treating hypoglycemia. While these limitations may make alternate-site meters less convenient and attractive to some, many people find that periodic alternate-site testing provides a welcome relief from the pain of fingersticks.

Originally Published May 18, 2006

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