BG meter vs. CGM reading

Have you ever wondered why your blood glucose (BG) meter and Dexcom G7 Continuous Glucose Monitor (CGM) reading are not the exact same number?¹

One explanation is that a BG meter measures glucose from the blood while Dexcom G7 measures interstitial fluid, so those numbers may be different. And, if your doctor did a lab test at the same time, the lab result may give a third number. The lab result is considered the most accurate number.

Other reasons there could be a difference between your BG meter and your Dexcom G7 are:

Hand cleanliness: Wash your hands with soap and water (not hand sanitiser) and dry them. Then test. Many inaccurate BG meter values are from hands not being washed thoroughly before testing.
Sensor’s first day: With newly inserted sensors, the differences between your BG meter and the Dexcom G7 reading may be greater. Generally, the numbers get closer over the first 24 hours.
Pressure on Dexcom G7: Sometimes when something is pressing on your sensor, for example, if you’re lying on it, it can affect your Dexcom G7 readings. Relieve the pressure and the numbers should get closer.
Glucose changing quickly: When your glucose is rapidly changing, it can be more difficult to compare your meter and Dexcom G7 because blood glucose changes a little before interstitial fluid glucose. The match should get closer when your glucose stabilisers.
Test strips: Make sure your test strips are stored as directed and not expired. Also, make sure to use enough blood on the test strip.

Calibration

Calibrating your Dexcom G7 is optional. It can make the Dexcom G7 more accurate or less accurate compared to the lab result, but it should bring the Dexcom G7 readings closer to your meter value.

When calibrating, make sure to:

Clean hands: Wash your hands with soap and water and dry them.
Enter within 5 minutes: Enter the calibration within 5 minutes of taking a fingerstick/finger prick.

Calibration Tips:

Pressure on sensor: If the sensor reading seems inaccurate because of pressure on the sensor, don't calibrate. The sensor should recover on its own when the pressure is relieved.
Stable glucose: Calibration works best when your glucose is stable. Consider waiting to calibrate if your glucose is changing rapidly.

Please contact Technical Support for product troubleshooting inquiries.
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1. Dexcom G7 User Guide

MAT-2899