I use the Dexcom G5 with the Dexcom app on a phone. I also use the Dexcom (new-style) receiver for “microwave technique” restarts so that I continue to get CGM data during the 2-hour restart warm-up. But when I actually change to a new sensor, until yesterday I hadn’t figured out how to continue getting CGM data during the first 2 hours, even though I think that some people on this site already know how to do it and all the pieces have been described here in various threads.
So I’m going to say simply how I do it. (I acknowledge that for folks using xDrip+ or Spike, they may not have the issue of no data during the 2-hour initial warmup.)
The first ingredient is the “microwave technique” for restarting a currently running G5 sensor when using the Dexcom phone app for primary CGM and a Dexcom receiver is available. It must be done more than 2 hours before the current sensor session expires. I actually do it on day 6 and 12 so that there’s no danger of running out of time. So here’s my version of "The Microwave Technique,"using the Dexcom app on a phone as my primary CGM, and the Dexcom receiver to help restart.
- Bring the Dexcom receiver within range of the transmitter and wait for it to connect to the CGM session that’s currently running on the phone. That generally takes 5 to 15 minutes.
- Wait for a fresh new CGM reading to arrive on the receiver.
- Wait 1 more minute, then within 2 minutes do the next 3 steps (must be before the next transmitter communication.)
- On the Dex receiver, Stop Session.
- On the Dex receiver, Start Session.
- Put the Dex receiver in a radio-proof container. I use a metal cookie tin. Some folks use an unused microwave oven. Some have a proper Faraday bag. Some folks just move the receiver way far away out of radio range.
- Wait at least 2 hours 15 minutes. (I don’t know if much much longer will cause problems, but a delay of 3 or 4 hours seems to be ok.)
- Remove the Dex receiver from the radio-proof container, wait for it to reconnect to the transmitter (typically 5 to 15 minutes), and then wait 5 minutes or less to get the “Enter first calibration” request on both phone and receiver.
- Enter the first and second calibrations on the phone, and put the Dex receiver away.
But what about when a new sensor is inserted? Other folks on this site have already told us that during a running sensor session you can pop the transmitter out of the old sensor and snap it into a newly-inserted sensor and it will continue to give readings with no warm-up time, but when I tried that I wasn’t getting good CGM data. Some folks live with it and just keep recalibrating until it seems to work ok, but I wasn’t happy with that, so I’ve been waiting 2 hours without data when I start a new sensor.
Yesterday I finally figured out how to fix that (after smacking my palm on my head to acknowledge being a slow learner). Simply stated, after switching the in-session transmitter to a new sensor, just do the microwave technique to start a new session without losing data. The detail is as follows.
When the sensor is still giving data but it is old and jittery so that I want to change to a new one—and more than 2 hours before the current sensor session will end (well before so there’s no danger of having the running session expire) do this.
- Insert a new sensor.
- Without doing a Stop Session, pop the transmitter out of the old sensor and insert it into the new sensor. The Dex app should continue to receive CGM data, perhaps missing one 5-minute interval.
- Calibrate if the CGM is reading wrong.
- Use all 9 steps of the microwave technique listed above to start a new sensor session while continuing to receive CGM data in the phone app. After 2+ hours, you’ll have a fresh new sensor session on a fresh new sensor, without having to go 2 hours without CGM data.
Or you could just use xDrip+, if that’s your preference.