Diabetes

Blood sugar testing results different

04/11/2005 01:37PM

Question:

I have fibromyalgia and carpal tunnel in both hands, I am not sure if this is a cause, I check my sugar level in my right finger and it was 165 in the am and I am on a no sugar lactose free diet. I checked my left finger and it was 142 then I checked my Arm and it was 129? I use the free style meter. I sleep habits are different so I sleep from 4am to 12 noon usually. I am also over weight and am currently working to drop weight. I also take several meds and my diabetic med is 30mg of Actos which I take each night. Why the difference is levels?

Answer:

Assuming the blood sugar meter is working properly, and that the meter is approved for arm testing, it is possible that blood sugar levels can be different depending on the site tested. For example, arm tests can be slightly less accurate than finger tests. The arm test result can include about a 20-30 minute "time lag" - meaning the result is not quite as up-to-date as the finger. Generally it is better to do a finger test (not an arm test) if you expect the blood sugar to be changing rapidly - for example, if feeling low or high, if eaten or exercised recently, or if ill.

To receive FDA approval, a blood sugar meter must be accurate to this extent - if you do two tests immediately following each other, using different fingers, or different places on the arm, the results should be within 20% of each other. The higher the blood sugar, the more the 20% variance can change the test result.

If you have specific questions about your meter and it's accuracy - call the manufacturer help line. The toll free number can be found on the back of your blood sugar meter.

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Response by:

Nancy J. Morwessel, CNP, MSN, CDE
Pediatric Nurse Practitioner
Diabetes Center
Cincinnati Children’s Hospital Medical Center
University of Cincinnati