Alternative Site Testing (AST)

Some blood glucose meters allow you to use blood samples from areas of the body other than your fingertip, such as the palm, forearm, upper arm, thigh, or calf. While this can give your fingertips a well-deserved break, alternate site testing is not always ideal. Blood from your fingertip reflects changing blood sugar levels rapidly. Because blood at alternate sites flows more slowly, there is a physiological lag time (often up to 20–30 minutes) before changes in your systemic blood sugar register there. Because of this delay, you may not always get an accurate reflection of your current blood sugar level.

Important: Always consult with your healthcare professional before you begin using sites other than your fingertip for blood sugar testing.

Alternative Site Testing (AST)

When You CAN Use Alternate Sites: Alternate site testing may be appropriate during periods when your blood sugar levels are highly stable, such as:

  • Immediately before a meal.
  • Fasted, first thing in the morning.
  • Right before bedtime.

When You Should NEVER Use Alternate Sites (Use Fingertips Only)

  • Do not use AST if you suspect your blood sugar is changing rapidly. 

Always use your fingertip during the following times:

  • After meals: Within two hours of eating.After exercise: During or immediately after physical activity.
  • During illness or stress: When metabolic changes are unpredictable.
  • After treating hypoglycemia: When you need to verify that a low blood sugar event has resolved.
  • If you have hypoglycemia unawareness: If you frequently experience low blood sugar without feeling symptoms.

Never ignore physical symptoms of low or high blood sugar. If your alternate site test result does not match the way you feel, perform a fingertip test immediately to confirm the result.  

References: 

1 American Diabetes Association. Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Supplement 1).                                                                                                                                                                                                                                                                              

Share
How helpful did you find this article?