On Friday, the Guardian Link 3 Transmitter for my Medtronic Minimed 670G Insulin Pump died. The transmitter is part of the Continuous Glucose Monitoring system (CGM) that is required for auto mode and for the pump to automatically adjust insulin delivery.

The transmitter quit working unexpectedly. I had just calibrated a new sensor. I got the error message “Sensor signal lost” and I moved the insulin pump closer to the transmitter. I waited about an hour but it did not connect. I then looked up how to troubleshoot this issue, and I came across instructions that said to try removing the transmitter and then adding the device again. (See instructions “Linking a Transmitter to your Pump“). It also said to put the transmitter back on the charger for a few minutes. I did that as well, and multiple attempts to connect resulted in the sad “No devices found” error.

I called Medtronic customer support and got technical help right away. They walked me through steps over the phone and when that didn’t resolve the issue, they said that they would send a new transmitter to me overnight.

No CGM sensor reading all weekend…

Unfortunately because the transmitter quit working on a Friday, I am without a transmitter over the weekend. Without the transmitter working, the insulin pump doesn’t know what my blood glucose is, and won’t warn me of low blood sugar. The insulin pump also won’t automatically suspend the insulin if I’m going low. For these features which I rely on, it requires the transmitter, which transmits the sensor glucose reading to my pump.

The transmitter has an internal battery in it, and is only warranted for a year. I was out of warranty and perhaps I should have replaced it sooner, but it was working fine.

Without the transmitter working, I have to manually adjust the insulin basal rate as needed and monitor my blood glucose closely.

My Expired Freestyle Libre Still Works

Fortunately I refilled my Freestyle Libre prescription prior to switching to this pump, so I had a Freestyle Libre in my closet. It is expired by over a year but fortunately it still works. I’ve been comparing the readings with a blood glucose meter and the Libre is tracking quite closely. So this expired Libre is being a life saver, but still managing insulin dose is difficult and I got low blood glucose and high blood glucose. In short, it’s been a very stressful couple of days.

Until I get the new transmitter, I’m trying to accept my blood glucose running a bit higher because it’s harder to control. And the alternative is increased likelihood of lows. I’d like to avoid another hypoglycemic event.

The freestyle libre is better than not having anything, but this model doesn’t have alarms.

I also haven’t really gotten a basal rate fine tuned for night time because I’ve been relying on auto mode. My current basal rate is a bit high at night so I set a temp rate and that got me through the last couple of nights. I’m really being extra cautious until I get the transmitter because hypoglycemic events are scary and can do damage. I want this to be a “no medical event” day, please!

Lessons Learned

• Buy a new transmitter before it dies, if you can.
• Expired Freestyle Libre still works. Diabetes medical equipment may work after the expiration date.