What Are CGM Supplies? A Guide to Sensors, Transmitters, and Extra Supplies

If you're new to continuous glucose monitoring, the phrase CGM supplies can be a little confusing. A CGM isn't always just one device. Depending on the system, there may be sensors, transmitters, receivers, readers, and other components involved.

It gets even more confusing when you switch systems and suddenly have unopened supplies left over that don't work with your new device.

Understanding what each component does can help you keep track of what you need, identify exactly what you have, and figure out what to do with factory-sealed supplies you no longer plan to use.

What Counts as CGM Supplies?

CGM stands for continuous glucose monitor. These systems track glucose levels throughout the day and can send readings to a compatible receiver, reader, smartphone, or other supported device.

The term CGM supplies can refer to several different components, including:

• CGM sensors
• Transmitters used with certain systems
• Receivers or readers
• Applicators included with certain sensors
• Other system-specific components and accessories

Not every system uses all of these components separately. Newer CGM designs may combine parts that older systems treated as separate pieces.

That's why it's important to know the exact system and generation you're using instead of thinking of CGM supplies as interchangeable products.

What Are CGM Sensors?

The sensor is the component responsible for measuring glucose levels. It's worn on the body for a specific period before being replaced.

How long a sensor is designed to last depends on the exact product. Different systems have different wear periods, so there isn't one replacement schedule that applies to every CGM sensor.

Sensors are also one of the supplies people are most likely to have extras of because they're replaced regularly.

For example, someone may receive a refill and then switch to another CGM system before opening all of the sensors they already have.

If you're interested in how a specific sensor's supply is calculated, our guide to Dexcom G7 sensor day supply explains how the replacement period can translate into the number of sensors someone may need over time.

What About Transmitters, Receivers, and Readers?

This is where CGM terminology can get confusing.

Some CGM systems have used a separate transmitter that works with the sensor to send glucose information to another device. Other systems integrate the transmitting technology into the disposable sensor itself.

A receiver or reader is used to display or access glucose information with systems that support one. Depending on the CGM, a compatible smartphone may also be able to perform some of these functions.

The important takeaway is simple: don't assume a sensor, transmitter, reader, or receiver from one system will work with another.

Even products from the same manufacturer can differ between generations.

Why Do CGM Supplies Vary Between Systems?

CGM systems are designed as specific product ecosystems. The sensor, software, transmitter when applicable, and display options are designed to work with particular products.

That means "CGM sensor" isn't specific enough when you're trying to identify a product.

For example, Dexcom G6 and Dexcom G7 are different systems. FreeStyle Libre also has multiple generations with different products.

This becomes especially important if you have unused supplies you'd like to sell. A buyer needs to know the exact product, not simply that you have "Dexcom" or "Libre" supplies.

How Often Do CGM Supplies Need to Be Replaced?

There's no universal replacement schedule for continuous glucose monitoring supplies.

Sensors have manufacturer-defined wear periods that vary by product. Separate transmitters, when a system uses them, follow their own replacement requirements. Readers and receivers aren't replaced on the same schedule as disposable sensors.

If you need to know when a particular component should be replaced, use the instructions for that exact CGM system rather than applying the schedule from another product.

This is also why someone switching systems can easily end up with extras. Supplies purchased for the previous system may no longer be useful once the change is made.

Why Do People End Up With Extra CGM Supplies?

There are plenty of ordinary reasons someone might have unopened CGM supplies left over.

A person may switch CGM systems after receiving a refill. Their prescription may change. Insurance coverage may change which product they use. Or they may simply have unopened supplies remaining that they know they won't need.

Instead of leaving those boxes untouched until they're too old to qualify, it's worth checking whether they're currently accepted by a buyer.

If you're specifically looking for somewhere to sell extras, our guide to choosing CGM buyers explains what to look for before sending your supplies.

Why Do Expiration Dates and Packaging Matter?

If you have unused CGM supplies, being unopened doesn't automatically mean they'll qualify for resale.

Buyers may have specific expiration requirements for different products. Packaging condition can matter as well.

Before requesting a quote, look for:

• The expiration information
• Factory-sealed packaging
• Damage to the box
• Moisture or staining
• Missing or unreadable product information

Don't assume one expiration rule applies to every sensor or CGM product. Test Strip Buyers explains this further in its guide to CGM expiration rules for Dexcom, Libre, and test strips.

Checking sooner rather than later can also matter. If you already know you won't use an unopened product, waiting until it's close to expiration may limit your options.

How Do You Identify the Exact CGM Product?

Before trying to sell unused CGM supplies, grab the actual package and read what's printed on it.

Check:

• Brand
• System or generation
• Component type
• Quantity
• Expiration information
• Reference, product, or other identifying codes when applicable
• Packaging condition

Be specific. "CGM sensors" or "Dexcom supplies" isn't enough information to accurately identify what you have.

A Dexcom G6 sensor, G6 transmitter, and G7 sensor are different products. The same principle applies to other CGM systems.

Matching the exact information on your box to the buyer's current product listing can help prevent quote discrepancies later.

Have Extra CGM Supplies You No Longer Need?

If you have factory-sealed continuous glucose monitoring supplies that you know you won't use, don't start by guessing what they're worth.

Start by identifying exactly what you have.

Check the product, generation, quantity, expiration information, and condition of the packaging. Then compare those details with the buyer's current catalog.

Accepted products, expiration requirements, and payouts can change over time, so current listings are more useful than an old quote or article.

Check the current Test Strip Buyers catalog to see whether your exact CGM supplies are currently accepted and what they're worth.