How to Test Your Blood Glucose Level

By Alan L. Rubin

All blood glucose meters require a drop of blood, usually from the finger. To get the drop of blood you need to perform a glucose test, you have to use a spring-loaded device that contains a sharp lancet. You push the button of the device, and the lancet springs out and pokes your finger. Devices that allow different depths of penetration are useful for small children.

You place the blood on a specific part of a test strip and allow enough time, usually between five seconds and one minute, for a reaction to occur. Some strips allow you to add more blood within 30 seconds if the quantity is insufficient. The need for a second stick of your finger is rare if you use a test strip that requires less blood. In less than a minute, the meter reads the product of that reaction, which is determined by the amount of glucose in the blood sample.

Keep the following tips in mind when you’re testing your glucose:

  • If you have trouble getting blood, you can wrap a rubber band around the point where your finger joins your hand. You will be amazed at the flow of blood. Take off the rubber band before a major hemorrhage occurs (just joking).

  • Testing blood from sites other than your fingers is generally reliable, except for an hour after eating, immediately after exercise, or if your blood glucose is low. These other sites don’t reflect the rapid changes in blood glucose that are occurring.

  • Some meters use whole blood, and some use the liquid part of the blood, called the plasma. A lab glucose tests the plasma. The whole blood value is about 12 percent less than the plasma value, so you need to know which you’re measuring. The various recommendations for appropriate levels of glucose are plasma values unless specifically stated otherwise. Most of the newer meters are calibrated to give a plasma reading, but check yours to be sure.

  • Studies have shown that the quality of test strips, which are loose in a vial, deteriorate rapidly if the vial is left open. Be sure to cap the vial. Two hours of exposure to air may ruin the strips. Strips that are individually foil-wrapped do not have this problem.

  • Check the expiration date of the strips. Expired strips won’t give correct results.

  • Don’t let other people use your meter. Their test results will be mixed in with your tests when they are downloaded into a computer. In addition, a meter invariably gets a little blood on it and can be a source of infection.