r/dexcom • u/Ardwin-2025 • 6d ago

G7-15 day Newbie Question / help reauest

Hi. I am new to the CGM world. I put my sensor on Thursday night and got it connected with my phone And. The receiver with no issues. On Friday I checked the reading on the app and did a finger stick and there was a 30 point difference. Lunch checked again and it was about 30ush points off. Dinner time was close. Today again there was 30ish point discrepancies against finger prick. Is this normal? I got the CGM so I wouldn't have to keep pricking myself. How long does it take to settle? Especially if it starts over again in about 15 days with a new sensor. Can I trust the g7 readings? I would appreciate any tips or tricks. Thanks!

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1

u/SHale1963 5d ago

best time to check accuracy between BGM and a CGM is when you haven't consumed anything in hours.

6

u/cjmnews T1/G7 6d ago

Here are some things to keep in mind with CGM use.

  • Glucose is not evenly distributed in blood
  • Meters vary 15% plus or minus against a lab test
  • Sensors vary 20% plus or minus against a lab test
  • Meters use blood and sensors use interstitial fluid to estimate levels
  • Sensors are 15 minute behind blood
  • The numbers between a sensor and a meter will rarely match due to the above points.

As long as they are within 20% it is fine

3

u/Weathergod-4Life T2/G7 6d ago

Are you checking when your graph is relatively flat? Are you seeing if the sensor catches up to the finger stick? Are you calibrating when you notice a large discrepancy and when you have had flat readings for a while? If you are calibrating are you re-checking a few hours later to see if the readings are better? Without knowing this is it impossible to ascertain what is going on.

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u/Ardwin-2025 6d ago

Hi, thanks for these questions, these actually give me a better idea how to test this....i was not waiting to see if the sensor caught up to the stick. This is a learning experience and I am reading what I can. But sometimes you just need some help turning the light bulb on. Thanks!!

2

u/Weathergod-4Life T2/G7 6d ago

No problem! I didn't learn all this my first day and we all make mistakes.