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.
www.bd.com/us/diabetes/blood-glucose-monitoring/how-to-test/alternate-site/