What technically happens to a sensor that is past the label expiration date? Are they safe to use? Are they accurate to use?

Does anyone here know, without guessing or making up an answer, what technically happens to a sensor that is past the label expiration date? Are they safe to use? Are they accurate to use ? (note: Please do not respond with chiding about using old supplies. We have to pay 100% of the costs ourselves.) I know many are successfully keeping the G4/5 going a second cycle by re-setting it. Hubby wants to stay with G4, just read the sensors won’t even be available thru Dexcom in 2021. Thank you.

Hi @susanlily if you ask the question on a forum, you can’t control the types or responses. That being said, the sensor has to be sterile, because you put it under your skin. So the thing that actually expires is the sterility. Packaging and sterility process holds the product, clean for “at least” until expiry with probably 1/1,000,000 probability. So after expiry the risk is loss of sterility which increases logarithmically after the stamped date.

Unsterile sensors increase risk of infection. Some bacteria can be worse than others so the risk runs from nothing, to a puss filled abscess, all the way up to septic shock. I hope this is helpful.


I just wanted to say, if you want to use the G6 without the “bells and whistles” you can. You’re probably more familiar with the relative costs of the G4/5 vs the G6, but the G6 does last 10 days so 3 pretty month rather than 4.
I’m impressed your husband had been able to get them to last so long - I hope you are able to use them. There’s a new Freestyle Libre (the Libre 2) in the market - like Dexcom it has alerts. You do have to swipe the receiver across the transmitter periodically but it should be a less expensive option to look into.

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@joe, @wadawabbit, have given you wise council. @susanlily, the battle between good health care and the cost of good health care is a ferocious fight for many.

I will do my best to give you scientific answers to your questions or point you to the ‘source documents’ containing the answer. A source document is the original first occurrence of a fact. For example, what is a person’s correct name? The source document is their birth certificate because it is the first record of the individual’s name created by their parents in the beginning.

Technically, what happens to a sensor past expiration? (1) sterility of packaging seals - look for info about the sealing method. (2) reagents on the sensor wire - look to the Dexcom patent filings for the method the stuff is put on the wire & tests determining its life & breakdown.

Are they safe to use? This is an opinion extrapolated from the sterility and component stability answers above.

Are they accurate to use? This is another opinion question whose answer is derived from the component stability answer above.

There are several groups on Facebook where people discuss using different models of Dexcom outside the published guidelines and approvals.

If you share your general location, and indicate a need for help, I believe another person here may be able to point you to CGM resources in your locality.

Please share what you decide. By sharing, we all learn, making T1N a better place for us all.


I have used several expired Medtronic Guardian Sensor 3 over the past few weeks, and overall they have worked without too many problems. The only things I have noticed are that it doesn’t last quite as long between calibrations (which can end up being in the middle of the night), and that it might fail a couple days early.

I’m not sure what exactly happens to the sensor itself past the expiration date, but so far it hasn’t been too much trouble to use expired ones. It may be different for other versions/companies.

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This is a purely personal opinion; but as I see it expiration dates - like pregnancy delivery dates - aren’t cast in stone. It’s not like you flip a switch and suddenly the thing stops working. Instead I look at them as a guideline, keeping in mind that the item’s end of life will be coming soon and that I should expect some degradation of performance. How long that might take is any body’s guess so I will use the item, but with caution until I start having issues.

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Please forgive me for going a bit off topic, but I’m curious as to how you’ve managed to extend your transmitter as well as your sensors? As I recall from my experience with the G5, it had to be replaced periodically - I don’t recall the G4 at all.
I get that you are frustrated and/or angry about not getting definitive responses to your question. Some of the responders are people with huge experience and wisdom with diabetes, who are very analytical about both diabetes and the technology and have done impressive “technical chops.” However I don’t know that any have worked in the CGM field or an area where they can give a definite answer. As with most things on the forum, we give the best suggestions we can based on personal experience and knowledge.
I have heard that Dexcom’s customer support has gone downhill - in my case it’s just taken me a bit longer to get through than it used to so I guess I have been fortunate. But I think if you want “the” answer to your question you need to go to the source - inconvenient though it may be. Aside from calling tech support another couple of additional ways to do that would be

  1. Contact your Dexcom rep - if you don’t know who yours is, check with your endo - I think they are assigned to doctors offices. Or
  2. do a Google search to see if you can find the tech specs - something along the lines of the brochures that come with medications, with diagrams of molecules that only a chemist can truly understand and appreciate. I imagine you are shaking your head here, but buried deep in there, you may find what you need.

I appreciate your frustration. You’re boxed in, your options are limited and less than ideal, and you need some hard and fast information. People on the forum do what they can to help but the answers you need may lie with the source - Dexcom.
I do wish you the very best and hope you are able the stretch out the sensors and transmitter to last until you have the resources you need.


i couldn’t disagree more. CCI and packaging integrity degrades over time. it’s fact.

we don’t attack each other on this forum, it is not helpful.


@susanlily. @wadawabbit. @joe @Dennis. Help me understand, Lily. Please restate your questions from your original post. Having another chance at them helps me check my knowledge base.