What Is a Glucometer and How Does It Work? An FAQ

Glucometers FAQs - General Questions

OneTouch Verio IQOneTouch Verio IQWhat is Dignifyed?

Dignifyed is an online resource devoted to reviewing technology and services aimed at preserving seniors' independence and quality of life.

How many hours of hands-on testing and research did you perform for this review?

We spent over 80 hours researching the best glucometers on the market. We started with 30 models and narrowed down our choices to the best 10 glucometers to do our hands-on evaluations and reviews.

What did you test?

Because of the level of testing that would have been required — and given that glucometers must meet specific FDA regulations for accuracy — we did not test the accuracy of the glucometers we reviewed. Instead, we researched glucometers and evaluated them based on their design, features, cost and ease of use. You can read more about our evaluation and research process here.

FAQs About Glucometers

How does a glucometer work?

Glucometers provide readings by detecting the level of glucose in a person's blood. To get a reading, a person pricks the skin — most commonly, a finger — and applies the blood sample gained to a test strip inserted in the meter. The glucose in the blood reacts with the chemicals in the strip. Then, electrical currents pass through, determining the level of glucose in the sample and providing numerical results within seconds.

True Metrix AirTrue Metrix Air

What types of glucometers are there?

Self-Monitoring Blood Glucose (SMBG) Meters: These are the most basic and typical meters that utilize test strips and small blood samples. Meters and test strips are available over the counter in stores and online.

Continuous Glucose Monitors (CGMs): This type of monitoring requires a sensor to be implanted under the skin to take readings every few minutes throughout the day and night. They require approval from — and implantation by — your medical doctor.

Noninvasive Glucometers: These meters do not require blood samples. Rather, they sense glucose levels through blood-rich areas of the skin. However, this technology is still being developed and tested, so these meters are not yet available in the U.S. market.

For more information on the different types of glucometers, read Which System Is Best?

What is coding?

Coding is essentially calibration for your meter when you start a new batch of test strips. To ensure the meter adjusts for variations in strip manufacturing, you enter a code provided by the manufacturer that tells the meter how to adjust its readings. Automatic coding is prevalent in newer models, so you may never have to worry about coding. The only glucometer in our reviews to use coding is the OneTouch Ultra 2.

OneTouch Ultra 2OneTouch Ultra 2

Do I need a backup glucometer?

We recommend having a backup glucometer, for a few reasons. The primary purpose of a backup glucometer is to double-check an unusual reading; if a reading is abnormally high or low, you can get a second reading with your backup device to help determine if the first reading was correct. A second reason is that, if you run out of strips and you cannot immediately get more, you can use the backup until you have more strips.

What does a glucose meter cost?

Glucometers are relatively inexpensive, generally ranging from as little as $5 up to around $30. The main expense with glucometers comes with the test strips, discussed below.

What features do self-monitoring meters offer?

While all meters work essentially the same way, not all offer the same features. Standard meters have digital screens, battery power sources and internal memory, and many have associated apps for data storage. Some offer only desktop apps, while others have smartphone apps that receive data from your meter via Bluetooth. Other features may include backlit LCD screens to read numbers more easily, USB rechargeable battery packs and even advanced features like voice technology that reads your results aloud — a great option for people with poor eyesight.

Where should I store the meter and strips?

You'll want to keep your meter, test strips, lancets and other supplies in a carrying case, which most glucometers include with the initial purchase. Test strips should be kept in their original vial or container, and you should make sure it is completely closed after each use. Keep all items out of extreme temperatures, direct sunlight, moisture and humidity, as any of these external factors can affect your meter and strips, causing false readings.

FAQs About Test Strips & Lancets

FORA Test N'GoFORA Test N'GoHow do test strips work?

While test strips are not interchangeable, and each company has its own proprietary technology, they all work and provide readings the same way. Test strips have absorbent channels that soak up blood to obtain a sample large enough for a proper reading. Once the blood is absorbed, the glucose in the blood reacts with chemicals in the strips. The reaction is detected and read by an electronic circuit that sends a signal to the meter's computer, which then converts it to a number.

What are lancets? Does the gauge size matter?

Lancets are spring-loaded needles that puncture a little hole in your skin to provide a small sample of blood for testing. Different gauge sizes create different-sized holes, and the smaller the number, the larger the hole. For example, a 28-gauge lancet will make a larger hole than a 30-gauge.

Some companies offer their own lancing device, in which case they use proprietary lancets as well. However, you can use any lancet you choose. Many lancing devices offer depth settings, which are personal preferences for your own comfort level. The only goal is to ensure you can obtain a proper sample size for your particular meter.

How much do test strips cost?

The cost of test strips can vary greatly and will add up over time, especially for people who test several times per day. We researched numerous online pharmacies and brick-and-mortar establishments and found that some companies charge as little as 22 cents per strip, while others cost a couple of dollars per strip. If your insurance doesn't cover diabetic testing materials, you may want to choose your meter based on the strip cost. At the very least, just know that you don't have to choose a meter whose strips are $2 a piece.

Can strips be used in different meters?

The short answer is no. Companies have their own proprietary technology, so strips are not interchangeable among different types of devices. Some companies may use the same strips in different models of their own design, but that's not always the case. For this reason, we highly recommend that you know where you can purchase strips before you decide on a glucometer. Some strips are more widely available than others, and some are sold only online.

AgaMatrix Presto ProAgaMatrix Presto Pro

Can I reuse test strips or lancets?

No. Test strips are single-use only. Many models can detect if a strip has been used and give an error message if you try to reuse a strip. And if you try to reuse a strip, there's no way to know if you're getting an accurate reading of your current glucose level because the chemicals that create the reaction have been used and compromised by the past sample.

Likewise, lancets should be used only once, both for sanitary reasons and because they can become dulled with use, making them less effective and more painful. Substances such as rubbing alcohol aren't an option for disinfecting because they can remove protective coatings on the needle.

Do test strips expire?

Yes, test strips expire, and the date will be clearly marked on the vial or bottle. Expiration varies from brand to brand, however. Some simply have an expiration date, while others are good for a certain number of months after you open the vial.

How should I dispose of test strips and lancets?

Individual states and regions may have specific regulations or locations for the proper disposal of used strips and lancets, so you'll want to verify the process locally or ask your doctor. However, in general, the best way to dispose of them is in a puncture-proof heavy plastic bottle with a screw-top lid or a store-bought sharps disposal container. Strips can be disposed of along with lancets.

FAQs About Testing & Results

Contour NextContour NextHow often do I need to test?

We are not medical professionals, so you'll have to consult your doctor to determine how often you need to test.

Can I take blood samples anywhere besides my finger?

The most common location for obtaining a blood sample is the fingertip. However, some meters offer alternative-site testing, which allows you to take samples from other locations, such as your palm or arm. This can give your sensitive fingertips a break from time to time, but in general, it's less accurate than fingertip samples. You should not gather alternative-site samples unless your meter specifically supports those sites, because if they don't, the readings may be unreliable.

How much blood is required?

Blood samples are measured in microliters (µL) — millionths of a liter. This works out to a very tiny drop of blood; most meters require only about 0.3 to 0.6 microliters, though some we reviewed required up to 1.0 microliter. Not enough blood can result in falsely low readings, so be sure to provide enough for accurate results.

How long does it take to get results?

The best glucose meters provide readings within a few seconds; the average is 4 to 5 seconds.

How accurate are readings?

All meters must meet specific accuracy standards set forth by the FDA. However, even these regulations allow for a margin of error. The regulations state that each device must be accurate within 15 percent of the actual blood sugar levels, 95 percent of the time. Beyond the accuracy of the meter, external factors can affect results, as discussed below.

Accu-Check Aviva ConnectAccu-Check Aviva Connect

What can affect readings?

Many factors can affect test results, so you'll want to eliminate anything problematic. As mentioned above, having an insufficient amount of blood in the test sample can result in falsely low readings, and if the sample site is not properly cleaned, contamination can affect the readings. Storing the meter or strips at extreme temperatures can cause falsely high or low readings, as can an improperly calibrated meter. Because of these factors, we recommend having a backup glucometer to double-check any readings that seem abnormally high or low. 

What should my blood glucose level be?

Normal blood sugar levels in a person without diabetes range from 70 to 100 milligrams per deciliter (mg/dL), and can potentially reach up to 120 mg/dL after meals. However, in people with diabetes, the levels may be higher. The American Diabetes Association suggests glucose levels of 80 to 130 mg/dL before meals and less than 180 mg/dL one to two hours after eating, but you should discuss your specific target with your doctor.

How can I track my results and data?

All glucometers in our reviews have internal memory that store a limited number of readings. We saw as few as 300 readings with the AgaMatrix Presto Pro, and as many as 1,000 with the True Metrix Air. However, most glucometers have an app to store data; some are desktop apps where you can transfer data through a cable, as is the case with both OneTouch models we reviewed, and some are smartphone apps with Bluetooth connectivity, like those offered by FORA TN'G and TN'G Voice. Apps can help you track readings and data to help recognize patterns in your glucose levels and behaviors that may affect them.