Medtronic 670G Sensors Not Lasting Full 7 Days

I’ve been using the 670G with sensors for over a month now, and I’ve noticed a troubling pattern. The sensors worked perfectly the first two weeks of use, as in they lasted the full 7 days before it tells you to switch out. However, every sensor after that hasn’t. The last two lasted 6 days before getting indefinitely stuck in the dreaded “Sensor Updating” cycle, with the pump eventually saying to switch it out. As I’m typing this, I’m on day 5 of the sensor I have in right now, and it’s back in that cycle, and history is leading me to believe that this one is toast now too. I’m getting trained on Auto Mode tomorrow(so at least I’ll have a fresh sensor), and will definitely bring it up to the nurse and Medtronic rep(will update this post afterward), but I’m worried if this keeps happening, will I even be able to do Auto Mode without much trouble. Does anyone else using the 670G have this problem? Is it possible I just got a bad batch of sensors?

I want to mention that I’m otherwise very happy with this pump. When the sensors work, which so far is most of the time, it’s amazing. Just concerned about potentially going through sensors faster than they’ll supply me for :confused:

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You should call tech support. they will replace (for free) any sensor not lasting as long as they are approved for. I got at least 22 replacements from MM when I used Enlites. Give them a call and explain what’s happening and they’ll send you replacements. Some of the techs will try to wear you down with a million questions.

The literature actually says 5-7 days. I dug into the question and found one thing to explain a bit of the issue. Medtronic reports that large swings in blood glucose may cause the sensor to last less than seven days. I notice this in my own use. When my blood sugar is porpoising (large swings up and down) the sensor definitely lasts less than seven days. When I have my blood sugar in reasonably good control the sensor will routinely last seven days. I hope that helps explain what may be going on.

Note: I am a Medtronic ambassador. My opinions are my own. They did not pay me to say nice things about Medtronic devices or the company. OK, they sent me a shirt and a cup but even I am more expensive than that.

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I figured that might have something to do with it. The sensor actually did come back, and I may not even bother bringing it up at training tomorrow. I’m actually OK with changing at 6 days, that way I can change both the sensor and infusion site/reservoir at the same time(I make it so my reservoirs last three days). Thanks for the insight! :slight_smile:

I’ve only hit the dread “Sensor Updating” thing once, so probably this isn’t news to you, but when I called MT tech support, after many questions, the fix turned out to be rather simple: switch the sensor off and back on again–basically a reset.

Options > Utilities > Sensor Settings, turn the sensor off, then back on again, then Sensor Settings > Reconnect Sensor.

Probably doesn’t always work, but worth a try–it did for me.

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I have the same issues with the 640G Sensors. I have batches that just dont seem to last. After I received a replacement 640G unit under warranty I now also get the sensor updating message…

When my sensor starts to have issues prior to the seven days, I disconnect the transmitter, Recharge it, and reconnect it. So far, the recharged sensors have all worked well for at least 6 more days and mostly for 7.


As others have mentioned, wild swings in BG can cause this. Also, when starting a new sensor, if youre high, it can cause problems. This brings up the topic of ISIG. I suggest searching the forum for this and reading up on it. Here’s a couple threads on the subject:

Additionally, I have found when the little flexible part that is inserted into your body get bent, kinked, or otherwise interrupted, it can cause this issue as well.

I Medtronic rep told me that you should devide the isig number into your BG number and if the result is outside of the range of 2 to 16, a calibration will not be accepted.

My sensors used to last seven days, which fit my schedule nicely. However, the last seven sensors have all gotten the Sensor Updating message, followed by Bad Sensor, Change sensor. I was requesting replacements via calls to Medtronic, but then they told me about being able to do that online. Then I was requesting them on their web site, until I got a message saying that I couldn’t request anymore (limit of five in 90 days). It turns out they meant, I couldn’t request anymore online. I just called and got another replacement.

Mine are failing in less than six days now. I don’t have any real wild swings of BG. My BGs are fairly close to my SGs at the time of the Updating Sensor message. My ISIG values are above 20 before the message.

Very strange. I just got 14 days out of my last sensor. I recently bought expired sensors on E-bay and I am currently on my 11th day without any major issues.

My Guardian 3 sensors last about 5-6 days, sometimes less. Not 7.

I’d like to know how that works. The Guardian 3 sensors are not designed for 11 days.

Medtronic, for safety/legal reasons, say they should not be used for more than 7 days. However, I bought expired G3 sensors at substantial savings on E-bay. The first 4 sensors so far each lasted 14 days (recharged trainsmitter after 7 days)without experiencing any issues.

Are you advocating that PWD should ignore the manufacturer, purchase used sensors on eBay, and use them beyond the recommended life?

I am not advocating anything. I am saying I can’t afford $345 per box of five and found a way to get my 670G pump to work in auto mode without draining my savings. I am willing to take the risk of extending the life of the Guardian sensor beyond what is recommended by the manufacturer in order to maintain my BGs under control.

As long as my sensor readings remain similar to my finger stick readings, I will continue to do so. Others not willing to take the risk may want to play according to the manufacturers’s recommendation which is fine with me.