What Is a Test Strip? How Blood Glucose Testing Strips Work

Blood glucose test strips may be small, but they're an important part of traditional blood glucose testing. If you've ever used a glucose meter, you've probably handled plenty of them without giving much thought to what's actually happening inside each strip.

They're more sophisticated than they look.

A testing strip works with a compatible glucose meter to analyze a small blood sample and produce a glucose reading. But not every strip works with every meter, and factors such as storage and expiration can matter.

Here's a closer look at what blood glucose test strips are, how they work, and what you should know if you have unopened boxes you no longer need.

What Is a Blood Glucose Test Strip?

A blood glucose test strip is a small, disposable strip designed to work with a compatible blood glucose meter.

One end of the strip receives a small blood sample. The strip contains chemicals that react with glucose in that sample, while the meter processes the resulting signal and displays a glucose reading.

The important thing to remember is that the strip isn't a standalone testing device. The test strip and glucose meter work together as a system.

That's also why grabbing a box of testing strips simply because they're the right brand isn't always enough. You need the specific strip designed for your meter.

How Do Glucose Testing Strips Work?

Although the technology varies between manufacturers and products, the basic idea is fairly straightforward.

A compatible test strip is inserted into the glucose meter. When a blood sample is applied to the designated area of the strip, a chemical reaction occurs.

The meter measures the resulting signal and uses it to calculate the glucose reading shown on the screen.

All of this can happen within seconds, which makes it easy to forget how much is happening between applying the sample and seeing a number appear on the meter.

Different manufacturers can use different strip designs and testing technologies, which brings us to one of the most important things to understand about glucose testing strips: they're not universal.

Why Aren't Test Strips Universal?

Blood glucose meters are designed to work with specific test strips or families of strips.

That means you shouldn't assume a strip will work simply because the meter is made by the same company. A manufacturer may sell several glucose meters that use different testing strips.

For example, someone switching to a new meter may discover that the unopened strips they already have aren't compatible with the new device.

Before buying or using a particular test strip, check the meter's instructions and the manufacturer's current compatibility information.

This is also one reason people end up with extra boxes. A meter change can turn perfectly unopened strips into supplies that are no longer useful to that person.

Do Blood Glucose Test Strips Expire?

Yes. Blood glucose test strips have expiration information provided by the manufacturer.

Test strips contain materials involved in the testing reaction, so manufacturers establish storage conditions and expiration dates for their products. You should follow the instructions provided with your specific strips rather than assuming the same rules apply to every brand.

Expiration becomes especially important if you have unopened boxes you no longer need.

Test Strip Buyers may have different expiration requirements depending on the exact product, and the amount of time remaining can also affect its value.

You can learn more in our guide explaining how expiration dates affect test strip payouts.

How Should Test Strips Be Stored?

Proper storage depends on the manufacturer and the specific test strip you're using, so always follow the instructions included with your product.

In general, manufacturers provide guidance covering things such as acceptable storage temperatures, moisture exposure, keeping containers properly closed, and whether strips should remain in their original packaging.

Don't assume that storage instructions from one brand apply to another.

If you're keeping unopened boxes that you may eventually sell, protecting the packaging from crushing, tearing, moisture, and other damage is also a good idea.

Why Do People End Up With Extra Test Strips?

Having extra diabetic test strips is more common than you might think.

Someone might switch to a different glucose meter while still having unopened strips for the previous one. Their testing routine may change. They may begin using a continuous glucose monitoring system. Insurance or prescription changes can also result in a different brand of supplies being used.

Families sometimes find unopened diabetic supplies that belonged to a loved one as well.

Whatever the situation, those boxes can easily get pushed to the back of a cabinet and forgotten.

If you already know you won't use them, it's worth checking whether they're eligible to be sold rather than waiting until they're too close to expiration.

If you're new to the process, our step-by-step guide to selling test strips explains how it works.

What Should You Check on an Unused Box?

If you have extra test strips, start with the box itself.

Look for:

• The exact brand and product name
• The number of strips in the box
• The expiration information
• The condition of the packaging
• Whether the original packaging and seals are intact
• Any other identifying information needed to match the product to a current listing

Be as specific as possible. Two boxes from the same manufacturer aren't necessarily the same product or worth the same amount.

It's also important to leave pharmacy labels in place rather than trying to peel them off yourself. Removing a label can damage the box. Test Strip Buyers can handle applicable labels during processing.

If you're wondering what an unopened box might be worth, read our guide on how much test strips are worth and the factors that can influence a payout.

Have Unused Test Strips You No Longer Need?

If you find an unopened box of test strips you won't use, don't assume it's automatically eligible or that an old price you saw online still applies.

Accepted products, expiration requirements, packaging requirements, and payouts can change.

The easiest approach is to identify the exact product you have and compare it with the current catalog.

If it's accepted, you'll be able to see the current product information and determine what to do next.

Check the current Test Strip Buyers catalog to see whether your unused test strips are currently accepted and what they're worth.