Readings delay

I have just spoken to a nice lady about getting a Dexcom 7 plus in the UK. She was most helpful. I asked about the fact that the sensor doesn’t test from the blood and she said that there would be a delay in what the dex said the bg was and what it actually was but calibrating with my bg meter sorts this out.

Does anyone know what the actual amount of time it is on the delay? She didn’t say.

It can vary. Plan on about 15-30 minutes.

Several things can make it vary; such as, exercise, hydration and sensor location to name a few.

The real value of the device is the ability to identify a trend of going up or down and the rate of change.

So if the trend was downwards, and the Dex said 90, it could actually have dropped to hypo level in that time delay?

Hi Dee,

Dexcom uses a slightly different technology than its competitors. I have seen quotes of the Dexcom lag time being 3 - 5 minutes, whereas the competition is usually quoted at 20 - 20 minutes.

See the following link where Dexcom talks about the difference in its technology and the difference in lag time. I use the Dexcom and was told that I do not have to wait until my BG is stable to calibrate.

Yes. But the trend arrow shows when bg is dropping and how fast it is dropping. It is pretty easy to avoid severe lows with the Dex. The delay going down is shorter than the delay going up. For me the delay going down is 5-10 minutes.


If you haven’t seen Wil Dubois’ blog entry on this yet, I recommend that you read it. Wil, a T1 diabetic, is a doctor in New Mexico. He has been wearing and writing about CGMs for many years.

His December 3 and 8 entries review the Dexcom 7+. He is fun to read and knows his subject.

I agree with some of the comments already posted. I usually see a 15-20 minute lag when going up but a faster response going down. The trend and rate of change info is invaluable. If I see double down arrows (dropping at > 3mg/dl/minute) and I’m still at 120 or 100, it’s got my attention and I’m pricking my finger. Time to get the carbs ready!

The CGM has allowed me to safely lower my A1c from 7.2 to 6.5 in just 60 days. My next A1c is scheduled for the end of this month and if I can believe the data collected by my Dex (I use a computer to download and track my BG data.) then I should test at closer to 6%. My goal is now 5.5%.