How to Calibrate Dexcom G7: Easy Steps to Improve Accuracy

Continuous Glucose monitoring systems (CGM systems) are calibrated with blood glucose meters (BGMs). This calibration involves entering the blood sugar readings from a BGM into your CGM. As a result, your CGM adjusts its readings, which are either showing higher or lower than the accurate reading. While many individuals are asking ‘How to Calibrate Dexcom G7?’, as per the company, calibrating a Dexcom G7 is Not required. However, in case of incorrect blood sugar readings, there is an option to calibrate your G7 sensor.

Is Your G7 Really Giving Inaccurate Readings?

No, just a different reading from a BGM does not mean you CGM isn’t correct.
First and foremost, you need to understand the underlying difference between a CGM and a BGM glucose monitoring.

BGM: It measures your blood sugar directly from your blood, and thus requires finger pricking.
CGM: With the help of a micro-pin, it measures you blood sugar from your interstitial fluid which is right under your visible skin.

Interstitial fluid: This comes from blood capillaries and when new fluid comes in, the old one is drained through the lymph vessels. Varying among individuals, it can take between seconds to minutes for the new fluid to be formed.

This is why your CGM and BGM readings may show some unusual differences at times. Especially, during the times when your glucose is fluctuating swiftly, e.g., right after having a meal. At such times when your glucose is fluctuating rapidly, wait for 5 – 10 minutes for your CGM to catch your current glucose readings.

How Do I Know If the CGM Readings Are Correct?

When your glucose is not changing rapidly, there should be little difference between the CGM and BGM readings. As shared by PubMed, according to ISO 15197:2013 and the FDA, ‘At least 95 % of measured glucose values should be within either ±15 mg/dl of the averaged comparison values at glucose concentrations <100 mg/dl.’

This means if your BGM is showing a value of 80 mg/dl, your CGM value can be;
80 + 15 = 95 mg/dl
OR
80 – 15 = 65 mg/dl

The ISO and FDA has given a value of ±15 mg/dl, however, ‘What is the 20 rule on the Dexcom G7?’, the Dexcom has indicated a difference of ±20 mg/dl to be correct.
This means in case of a Dexcom CGM sensor, considering your blood sugar is not changing swiftly, if you notice multiple readings which are more than 20 mg/dl off your BGM readings, then you should consider calibrating your sensor. Thus, the answer to ‘Can you reset a Dexcom G7 sensor?’, is a ‘yes’, however, only when you notice certain facts.

How to Calibrate the Dexcom G7:

1. Open up the Dexcom G7 app.
2. Click ‘+’ on the top right corner.
3. Choose ‘Blood Glucose’ from the pop-up menu.
4. Choose ‘Use as calibration’.
5. Enter your BGM value and click ‘Save’.
6. It will give you an explanation. Click ‘I understand’.
7. Confirm if you have entered the correct number.

Your CGM sensor shall not abruptly change its measurements, but will slowly adjust itself.

Conclusion:

The answer to a common question, ‘Is Dexcom accurate without calibration?’, as per Dexcom, is a ‘yes’. However, when your Dexcom G7 sensor is giving readings which are too far off from your BGM readings in a state when your glucose levels are not changing rapidly, and you notice numerous such readings, consider calibrating your CGM sensor. Additionally, if you are considering switching your CGM sensor, you may want to have a look at Freestyle Libre 2 Plus Sensors, which are not only accurate but also AID compatible as well.

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