There is always a discrepancy when I test my blood glucose levels on one hand versus the other. This morning I tested my left hand and got a blood glucose reading of 153. I immediately tested my right hand, and it read 167. Why is this happening? Sometimes the difference is as much as 50 mg/dl.

Shelley Levey
Columbus, Ohio

Christy Parkin, MSN, RN, CDE, responds: Blood glucose levels vary from minute to minute, and from body part to body part. It is not unusual to see a difference of plus or minus 15 to 20 percent from one reading to another, and this is generally considered the industry standard for blood glucose meters. When meters are reading greater differences, it is time to evaluate other issues such as the integrity of the strips, the cleanliness of the skin, and the technique of obtaining a drop of blood and correctly placing it on the strip.

If you are using a meter that requires coding, make sure that the code is set to match the code on the bottle of strips being used. Since strips are very sensitive to air, moisture, and extreme temperatures, make sure that you re-cap your bottle of strips immediately after taking a strip out, and don't keep them in a cold or hot car, a bathroom with lots
of moisture, or near a window with lots of sunlight. You can also check your strips using the control solution that comes with your meter.

Sometimes it is helpful to go back to the basics you learned when you first started blood glucose testing. Make sure you are washing and drying your hands. Use a lancet device with the shallowest penetration that will get enough blood for the strip that you are using.

If you want to check the accuracy of your meter against a lab value, do a finger stick immediately after your lab draw (you should be fasting). Again, it is acceptable to see a plus or minus 20 percent variation. Medical conditions to consider are peripheral neuropathy, which can impair circulation, and edema (excess fluid in the tissues), which can also cause blood glucose variations.

It is always a good idea to call the customer service toll-free number on the back of your meter if you have questions and concerns about the accuracy of your meter and strips. Company representatives can help you troubleshoot many of the issues related to your concerns.