Alternate Blood Glucose Testing on Arm, Palm, and Thigh


Alternate site refers to testing blood glucose on parts of the body other than the fingertip: most commonly the forearm, palm or thigh.

Testing somewhere other than the finger may bring a sigh of relief to many people with diabetes.
However, alternate test sites are not all the same.

With all meters, routine testing on an unrubbed forearm, upper arm, thigh or calf gives a test result that is 20 to 30 minutes old.

We will call these sites 'lagging' alternative test sites.

The fingertips and the palm hold the most recent 'memories' of your blood glucose. Fingertip and palm testing tell you what your blood glucose level is right now.

On the other hand, lagging test sites such as the forearm or thigh tell you what your blood glucose was around 20 to 35 minutes ago - not what it is right now. That difference can be crucial if your blood glucose is dropping fast --- a forearm test might tell you that the level is fine, because the forearm is a lagging test site, while a fingertip test correctly alerts you to a low number. Because of this, lagging test sites cannot replace the fingertip or palm completely for any person.

Several monitoring companies give people the choice to test their blood glucose using alternative sites. However, lagging test sites such as the forearm or thigh are only reliable when your blood glucose levels are relatively stable, such as fasting blood glucose.

So when is alternate site testing not recommended? The U.S. Food and Drug Administration gives these guidelines:

1. People with hypoglycemia unawareness should not use alternate site testing at all.
2. Don't use alternate sites when a seriously low blood glucose might go undetected:

  • When you have just taken insulin, or any time during or after exercise.
  • When there are unknown variables occurring in your day, such as illness.
  • Any time you just feel "low".
  • Whenever you are about to drive.

Talk to your doctor to see if alternate site testing is right for you. With a little bit of education, you can give your fingertips a rest and maybe test more often than you do now. For people with diabetes, more frequent testing is a good thing. Just remember: any time you want to be sure of an accurate, up-to-date blood glucose reading, test on your fingertip or palm.


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