It is best to start a new Guardian 3 CGM sensor in the morning because it requires more frequent calibration on the first day. If you start it late in the day, the calibration alert will likely wake you up at night.

However, in my opinion, there is no time like the present to start a new sensor if your current one is expired or not working.

I struggled with this last week, as I have been wanting to switch to starting my sensor in the morning, but I also didn’t want to go to bed without a sensor on me. I realized that I would probably wake up in the middle of the night to check my blood glucose anyway, so if I was going to be up checking, I might as well be calibrating a new sensor…

I know some people use the Medtronic 670G Insulin Pump without the sensor, but I have always used the sensor. The auto mode prevents me from going low at night. I can’t use auto mode without the sensor.

How long does a Medtronic Guardian 3 CGM Sensor Last?

It is supposed to last 7 days. The 7 day countdown starts with your first calibration. The sensor status will show “1” day left when there is less than a day left.

Some people are able to restart their sensor and get up to 14 days on one sensor. To restart the sensor, you have to disconnect the transmitter from the sensor and then plug it back in, and tell your pump that you just connected a new sensor. It is also a good idea to charge the transmitter before re-connecting it. The tricky part of re-starting a sensor is removing the transmitter without removing the sensor. I’ve started using different over tape to make it easier to remove the transmitter. Pictured above, I am wearing GrifGrips tape over the transmitter, which I’ve had success on being able to pull off.

Sometimes, the sensor doesn’t last the full 7 days. If this happens to you, you should be able to get a free replacement from Medtronic. Keep the packaging for the sensor incase you need to request a replacement. They will want to know the lot number. You can request a replacement by calling Medtronic or by using their online form.

If you continually have problems with the sensor not lasting 7 days, you may want to try a different location. Arms and abdomen are the officially approved locations for placement. I use the back of my upper arm with very good success, but I have my husband help me, since it’s a difficult spot to reach myself. I’ve read about people using their upper or outer thigh. I tried that once and it didn’t work for me, but everyone is different. Good luck!