Understanding the expiration dates of your testing supplies is an important part of maintaining your health as someone with diabetes.

Welcome back to our weekly diabetes advice column, Ask D’Mine, hosted by veteran type 1, diabetes author and educator Wil Dubois.

A illustration of a bright red "help" button.

This week, Wil takes on a dual set of questions asking about expiration dates on those handy little strips we use to test our blood sugar levels — and whether there’s really any need to respect the stamped-on expiration dates. Take a peek at what Wil has to say… as well as what one of the big strip-makers tells us.

{Got your own questions? Email us at AskDMine@diabetesmine.com}


Beth, type 1 from New York, writes: I have been a “juvenile diabetic” since 1960 — when I was six years old. I have recently received 1600 glucose test strips for free. About 600 of them were expired. I did a little research, and decided that maybe the whole “expiration date” thing for test strips may not be true. I have been using these test strips for two months now. I occasionally test with my regular monitor and unexpired test strips to check the accuracy. Guess what? The results are the same –– maybe 5 points different. I have decided the expiration date on test strips is a ploy by the drug companies to suck us dry! Oh, yeah. The expiration dates were 2007 & 2008.

But in the same week….

Bob, type 1 from Sacramento, CA, writes: Over the last few days I have been getting higher than normal readings; 165-325 for no apparent reason. I noticed that my test strips “expired” 4 months ago… could this be the cause of my high readings? Thanks for any help!

Wil@Ask D’Mine answers: Excuse me while I stroll out onto a mine field here… Nothing in diabetes is more controversial than test strips. Their cost. Their accuracy. Their availability. Even their effectiveness as part of therapy. But as much as I usually enjoy beating a dead horse, today I’m going to avoid all of those hot-button topics and just focus on the issue of test strip lifespans.

First and postmost (new word alert!), regardless of the expiration date, test strips really do expire at some point. Second and foremost, that date may not be the one printed on the carton.

Let me explain.

Strips expire. Honestly, they do. Not that I wouldn’t put it past Big Pharma to engage in “a ploy to suck us dry,” but in this case, the facts are that the magical little enzymes and chemicals that make test strips work really do break down over time. A test strip is more animal and vegetable than machine, and any test strip that’s old enough will eventually give you bad information.

But is that point of bad information really the printed expiration date? The vial of Verio strips on my desk says it expires 08/2014. Does that really mean I’d get a good reading using one August 31st and a bad reading on September 1st? Of course not. That’s ridiculous. But what if I tried to stretch it to the middle of September? Or into October? Or into 2015 or even into 2016? Frankly, I don’t know. No one knows, or if they do, they are paid well to keep their traps shut. And as our two readers above demonstrate, it’s probably not just as simple as the age of the strip. Beth is happy with the results of years-old strips and Bob seems to be having issues with months-old strips.

There are other factors afoot.

Looking outside diabetes for a moment, I’ve been known to try to yank a carton of milk out of the back of the rack in the grocery store refrigerator in hope of getting a fresher one, because, as we all know, milk has a limited shelf life. Beyond that point, a process of decay sets in. First, it gradually turns sour, then it develops a foul odor. Next it gets chunky, then it grows brown, green, or pink mold (really) and eventually it turns into Limburger cheese (not really).

Just now I went into my kitchen and checked out our Wal-Mart Organic 2% milk. It has an expiration date, but there’s also a note saying that the product should be consumed within seven days of opening. Presumably, if you opened the container eleven days before expiration date, you’d still only get the seven days. So there are two clocks ticking with milk. One counts down spoilage in a pristine unopened container and the other counts down spoilage in use.

But of course there are actually more clocks running than that. Some brands of milk probably last longer than others. How far you need to transport the milk between buying it and getting it home to your fridge no doubt has a role to play in how long it lasts, as does the temperature in your part of the country and what time of year it is. Oh, and how long did the milk sit on the loading dock at the store while the stocking clerk was texting his new girlfriend? Going farther up-stream, did the delivery truck maintain its temperature correctly between the dairy and the store? How long did the driver spend enjoying his fave bacon-cheeseburger en route? And did your milk even come to your store from the dairy, or did it hang out at a distribution center first?

And, of course, milk spoilage correlates to the habits of the humans who co-inhabit your domicile with you, too. If you live with people who leave the carton on the table the whole time they eat their Post Toasties, I would think your milk would live a shorter life than if you live with people who return the carton to the fridge immediately after pouring it on their cereal. And we’re not even going to talk about the impact of people who drink directly from the carton.

Guess what? All the delivery, storage, and utilization issues that impact milk also impact blood glucose test strips, and the older they are, the more these variables stack up.

But wait. With test strips, there’s even more. While milk is either good or bad, test strips might be fine in the “normal range” after expiring, but begin to show errors at high or low ends of the blood sugar spectrum.

Also, milk is fundamentally milk, regardless of whose carton it’s in. But every brand of strip is fundamentally different. Different makers of test strips use different enzymes and chemicals to create their propriety systems. One company might choose a less stable enzyme that gives better accuracy at the cost of shorter life; while another might choose less accuracy for better long-term storage. Yet a third company will choose the cheapest alternative.

So there’s a whole host of factors beyond it’s inherent life based on its design and materials that affect the lifespan of a strip that are hard to account for. So, given all of that, let’s consider how a strip company might go about choosing an expiration date. Of course (in theory) they know exactly how long the damn things are good for, but we should also consider their liability, because I guarantee that they do. Let’s pretend they are 100% scientifically positive that the strip will last a year. In that case, they’d be crazy to put a one-year expiration date on the vial, even if (from our perspective) that’s the “right” and honest thing to do, because what if one shorter-lived strip got though, you used it, got bad info, made a bad decision, and died? They’d get their pants sued off, that’s what. So on that basis alone, they need to set the bar lower to protect themselves.

Taking all of that into consideration, I think most strips, if stored properly, can be used for a good period of time beyond their official expiration date. There’s enough of a cushion built in that we can stretch it, and not get a mouthful of spoiled milk. But at the same time, with all the variables that can impact a strip’s lifespan, and the tremendous variety of strips out there, I don’t think we have a prayer of getting a hard-and-fast rule about how long a typical strip might last.

Bottom line, I think strips are fine for some period beyond their expiration date, but I have no clue how long a typical strip might last. I think that the older the strip, the more likely it is that it will let you down.

Might there be a conspiracy to “suck us dry”? Maybe. Maybe not. But it’s my health at risk if I assume expired strips are fine, and that it’s all about the money. Personally, I’d use an expired strip before I’d go without testing… but I plan to continue reaching into the back of the refrigerator case for the freshest carton of milk I can get my paws on.

Editor’s note: For the record, we reached out to some of the big glucose test strip companies to get their take on expiration dates. This is a response we received from LifeScan, part of the J&J family that makes the OneTouch strips. The “official” word, as it were:

I can assure you that there is nothing arbitrary or deceptive about how test strip expiration dates are chosen and, in fact, it is not only in the best interest of the patient to have the longest possible product shelf life, but it also benefits the distributors of the product and the manufacturer of the test strips as well. Legally, the manufacturer must ensure the product performs as claimed in the labeling. To meet this requirement, at LifeScan, we conduct tests to monitor the performance of our test strips over time.  Once we determine how long after manufacture the test strip performance is valid, say 18 or 24 months, this information is used to calculate the expiration date that is applied to the strip vials at the time the strips are made.

It’s important to note that the active ingredient in a test strip is not stable forever.  Therefore, test strip performance does change over time and it will no longer perform as intended. It is important for patients not to use test strips beyond the expiration date as LifeScan cannot guarantee the performance of the product and incorrect results could pose a risk to patient health.  The FDA also warns patients not to use expired test strips.

In addition, expired product and product with short shelf lives constitute a business expense that must be managed.  Often we cannot sell product with a shorter than usual expiration date (short-dated product) because wholesalers, distributors and pharmacies are concerned that they will not be able to sell short-dated product in a timely fashion and it will ultimately need to be returned — which is costly from logistics standpoint.  In addition, we (the manufacturer) accept returns from channel partners for expired product, which must then be destroyed in a compliant manner at our expense.

Our goal is to have the longest possible shelf life while protecting patient safety by ensuring our products perform as claimed.

So it’s not as obvious as milk, perhaps, but the rules of product expiration still apply.

This is not a medical advice column. We are PWDs freely and openly sharing the wisdom of our collected experiences — our been-there-done-that knowledge from the trenches. But we are not MDs, RNs, NPs, PAs, CDEs, or partridges in pear trees. Bottom line: we are only a small part of your total prescription. You still need the professional advice, treatment, and care of a licensed medical professional.