When comparing results using a sample obtained from the forearm and from a fingerstick your patients should be in a fasting or pre-meal state (to have had no food in the last 2-3 hours).
If a large difference (>20%) between forearm and fingertip is observed when testing is done at the appropriate times, the patient should use fingertip testing for all treatment decisions until the reason for the discrepancies can be identified and resolved. Verify the system is performing properly using control solution. The forearm vs. finger test comparison should be tried again later to see if the same discrepancies occur. One single forearm/finger comparison should not be used to judge the success/failure of forearm testing.
Under certain conditions, blood glucose test results obtained using samples from the forearm may differ significantly from fingertip samples.
The conditions in which these differences are most likely to occur are when blood glucose is changing rapidly such as during the two-hour period following a meal, insulin dose or physical exercise.
When blood glucose is falling, testing with a fingertip sample may identify a hypoglycemic (low blood sugar) level sooner than a test with an forearm sample.