Flexible Insulin Therapy:
Blood Glucose Testing
Blood glucose testing is an important part of flexible insulin therapy (FIT). Your tests serve two purposes:
  • Each pre-meal reading helps you to fine-tune your insulin dose for that meal. This is called a correction dose.
  • Trends in your past readings can help you spot those times of day when your blood glucose is often too high or too low. These trends are called "patterns." Understanding your blood glucose patterns can help you and your doctor make necessary adjustments to your insulin therapy.

When to Test

With FIT, you should test your blood glucose at least four times each day. On some days, you may need to test six to eight times. You must test before meals and before bedtime, because those readings will help you adjust the insulin dose you take at that time. The four essential times to test your blood glucose are:

  • Before breakfast
  • Before lunch
  • Before the evening meal
  • Before bedtime
  • Testing at these additional times can help you fine-tune your basal and bolus insulin doses:
    • Two hours after breakfast
    • Two hours after lunch
    • Two hours after the evening meal
    • Occasionally, at 3:00 a.m.

It's important to keep track of your test readings so that you and your doctor can analyze them and act on the results. Newer blood glucose meters have memory and calculation features that make spotting high and low values easier. Some meters even have a time-specific averaging function that makes it easy to see patterns of high or low blood glucose. If you have access to a computer, you may find it helpful to use the pattern management software that works with your blood glucose meter.

Where to test

If you are serious about following FIT, then your blood glucose testing must be done in a consistent way. Fingertip testing is commonly used because it provides an accurate measure of blood glucose changes.

Some blood glucose meters allow you to use blood from other places on your body. (This is known as "alternate site testing.") These places are the upper arm, forearm, thigh, and the base of the thumb. It's important to know that blood glucose values from these sites may be different from the results you receive from a finger, because they may reflect blood glucose values from 10 to 30 minutes prior to the test.

The biggest difference between fingertip test results and alternate site test results can be seen when blood glucose is changing quickly (such as after a meal, after an insulin injection and during or after exercise). For that reason, fingertip testing should be used in the following situations:

  • If it has been less than two hours after a meal, insulin dose, or exercise.
  • If you think your blood glucose is low, or you suspect that it is dropping.
  • If you have a condition called hypoglycemia unawareness.
  • If the results you receive from the alternate site do not agree with the way you feel.

Fingertip test results are more accurate than those from alternate sites, so they allow you to adjust your bolus insulin doses more precisely. You can reduce the discomfort of fingertip testing by using the thinnest possible lancet to obtain a very small blood sample. You'll also need a blood glucose meter that provides test results using a very small volume of blood, less than 1/2 microliter.