Alternate Site Blood Glucose Monitoring — The Facts

Over the past few years, a debate has been taking place about the use of sites other than the fingers for monitoring blood glucose levels. Before filling you in on the debate, let’s make sure you have the background, know what the alternate sites are and are versed in the pros and cons of using them.facts

THE BACKGROUND

Since the early 1980s, when people with diabetes were introduced to blood glucose monitoring, they have been using their fingers to obtain blood samples. The fingers became the accepted source for blood for nearly two decades. As increasing numbers of people with diabetes started to manage their diabetes intensively, doing upwards of four to six blood checks per day, a need arose to be able to use alternate sites for blood samples. This need gave rise to manufacturers developing monitors that were accurate and approved for alternate sites.

Alternate sites

• Forearm
• Upper arm
• Fleshy side of the palm by the pinky
• Fleshy area between the thumb and index finger
• Thigh
• Calf

THE ADVANTAGES

The biggest advantage of alternate site testing is less pain. That’s because alternate sites have fewer nerve endings than fingertips. The second advantage is that you can give your well-worn, and possibly sore, fingers a rest. Third, you might be willing to check your blood glucose more often if there is less pain involved. Finally, alternate sites are less likely to have food, dirt, grease or other contaminants that can ruin the blood sample.

THE DEBATE

Several years ago, a couple of meters were approved by the Food and Drug Administration for alternate site testing. (The FDA is the government agency that approves medical devices, including blood glucose meters.) Following the approval, some research was published about the lack of accuracy of alternate site testing. The FDA grew concerned and did a thorough investigation. The FDA, after holding several hearings during which research was presented, was satisfied that alternate site testing was accurate.

A LAG TIME

The main concern is that there is a lag time in the flow of blood to sites other than the hands, such as the forearm and thigh. Although the lag time is short, it can cause blood test results to be less accurate when blood glucose levels are changing rapidly. This might happen during a low blood glucose period or just after eating or exercising vigorously. However, for most people, blood glucose levels change rapidly only a very small percentage of time during the day.

This lag time and possible loss of accuracy with alternate site tests is caused by the slower flow of blood in these parts of the body. The blood flows a bit faster in the fingers and hands because there are more capillaries (small blood vessels) than in alternate sites. These capillaries have a more direct connection to arteries and veins. The faster blood flow to the hands and fingers means that blood glucose gets to your fingertips faster. The results you get when using your fingers provide a number that is closer to your real-time blood glucose levels. The results from the alternate sites may have a short delay, or lag time. Again, this delay does not affect the accuracy most of the time. But the lag time may cause your reading to be higher or lower when your blood glucose is changing quickly.

WHEN TO USE AND NOT USE ALTERNATE SITES

The FDA now requires companies who make meters that can be used on alternate sites to tell you which alternate sites the meter is approved for and to tell you under what conditions it is OK to use these sites.

Here is the FDA’s general advice:

Use alternate sites when blood glucose levels are steady:

• Before meals/food intake
• 2 hours after meals/food intake when blood glucose has come back down

Use fingers (not alternate sites) to check blood glucose under these conditions (when blood glucose levels are changing rapidly):

• When you suspect your blood glucose is low. (FDA encourages people who aren’t aware of low blood glucose levels not to use alternate site testing.)
• Up to 2 hours after a meal/food intake
• Up to 2 hours after taking rapid-acting insulin (Humalog and Novolog)
• After exercising vigorously
• Before you drive a vehicle
• During an illness that is affecting your blood glucose levels

A FEW MORE WORDS OF ADVICE

• If you choose a meter that can be used on alternate sites, read the fine print in the materials that come with the meter.
• If you have further questions, contact the company using its toll-free number listed in the chart above, or ask your Walgreens pharmacist.
• If you use alternate sites for some of your blood glucose checks, let the health care provider who reviews your log books know. Make a note, such as an X or star, next to the tests you do on alternate sites. Also, as you review your records, see how the results from alternate sites compare to those from your fingers. This will help you decide whether alternate site testing is for you.
• Use your experience and instincts to help judge when and if you should use a finger or an alternate site to check your blood glucose level.

Note: pregnant women should not use alternate site testing.

TIPS FOR USING ALTERNATE SITES

• Vigorously rub the site you will use to check your blood glucose before you prick your skin. This increases blood flow to the area. Use soap and water to clean the site, not alcohol.
• Use just one brand of meter. Don’t alternate between different meters. This will help you get consistent results. (Note: This is true for all meters, not just meters for use on alternate sites.)
• Use the same alternate site consistently. For example, always use your forearms, but it is OK to switch from one forearm to the other.

Meters Approved by the FDA for Alternate Site Testing

Meter Manufacturer Contact Information
Ascensia Breeze, Elite, Dex, Dex2
Bayer/Ascensia
(800) 348-8100
Note: Company suggests using its Microlet Vaculance lancing device on alternate sites.

FreeStyle
TheraSense
(888) 522-5226
Approved for upper arm, thigh, calf and fleshy parts of the hand.
Precision Sof-Tact
Abbott/MediSense
(866) 763-8228
Approved for forearm, upper arm and base of thumb.

Ultra, UltraSmart, InDuo
LifeScan
(800) 227-8862
Approved for forearm and just above the elbow. InDuo: Ultra meter with insulin delivery device.
Active, Compact
Roche Diagnostics
(800) 227-8862
Approved for palm, forearm, upper arm, thigh or calf