Blood Glucose Monitoring Devices and How They Work

Key takeaways:

• Blood glucose meters, also called glucose monitoring devices, are important tools for tracking blood sugar levels.
• The two main types of blood glucose meters are standard meters and continuous glucose monitors (CGMs). 
• The accuracy of these devices for monitoring glucose depends on proper use, device quality, and environmental factors.
• Many glucose meters include features like data storage, quick results, and smartphone connectivity for better tracking.
• When choosing a meter, consider accuracy, ease of use, cost, and special features.

Diabetes is a health concern globally. Since 2000, the number of adults aged 20 to 79 with diabetes has tripled. At that time, an estimated 151 million people (4.6% of the global population) were affected. By 2023, this had risen to 537.5 million, or 10.5% of the world’s population. By 2045, the prevalence is expected to rise above 12.8%.

Blood glucose monitoring involves regularly tracking changes in blood sugar levels and identifying patterns. These fluctuations can result from factors like diet, exercise, medications, or health conditions such as diabetes.

Maintaining blood sugar levels within a healthy range helps lower the risk of complications like nerve damage, heart disease, and kidney problems. It also supports making smarter lifestyle choices and treatment decisions, promoting overall health and improved quality of life.

What are glucose meters?

Glucose meters, also called glucometers, or glucose monitoring devices, are small devices that measure the amount of sugar in your blood. They help people with diabetes track their blood sugar levels regularly. To operate them, you prick your finger to get a drop of blood, place it on a test strip, and insert the strip into the meter to see your results.

These devices help you understand how food, exercise, and medicine affect your blood sugar, making it easier to manage your health.

Glucose meters help manage low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia). The goal is to bring blood sugar levels close to normal, tailored to the needs of each patient.

Types of blood glucose meters

The two main types of blood glucose meters are:

•  standard blood glucose meters and 
• continuous glucose monitors (CGMs).

Standard blood glucose meters

The standard blood glucose meters are commonly used glucose monitoring devices. They usually require a drop of blood placed on a disposable test strip.  A meter is used to analyze this and provide a quick glucose reading. These meters are typically used multiple times daily to check glucose levels at specific times.

How to use them:

• Wash and dry your hands properly.
• Insert the strip into the meter.
• Prick your finger and obtain a small drop of blood.
• Drop the blood on the strip.
• The blood sugar level is displayed on the screen within seconds.

Features:

• Easy to use and portable
• Provide quick results.
• Keeps record of previous readings.
• They need test strips and require regular calibration.

Examples of brands:

• Accu-Chek (e.g., Accu-Chek Guide)
• OneTouch (e.g., OneTouch Verio)

Continuous glucose monitors (CGMs)

CGMs are advanced devices that monitor blood sugar levels continuously, day and night. They use a small sensor placed under the skin, usually on the arm or abdomen, to measure glucose in the fluid between cells.

Some CGMs can connect with insulin pumps and automatically pause insulin delivery if they detect low blood sugar. They do not need manual intervention. 

They are helpful for people who require precise glucose management. While older CGMs often needed two daily finger-prick tests for accuracy, newly inserted devices no longer require this step.

How to use them:

• Using a special applicator, place the sensor under the skin.
• Keep the sensor as your doctor recommends (usually 7–14 days, depending on the model).
• Using a compatible device or app, monitor glucose readings.

Features:

• Consistent glucose monitoring without frequent finger pricks.
• Send alerts when blood sugar levels are too high or too low.
• It is helpful for people who need strict blood sugar control or experience frequent changes in their levels.
• Some models connect with insulin pumps and provide automated insulin adjustments. These may be particularly ideal for people with type 1 diabetes who need to receive daily insulin injections.

Examples of brands:

• Dexcom (e.g., Dexcom G4)
• Freestyle Libre (e.g., Freestyle Libre 2)
• Medtronic Guardian Connect

How accurate are these devices?

The accuracy of blood glucose meters (BGMs and CGMs) has greatly improved. However, it can still be affected by factors like the device used, how it's operated, and environmental conditions. Although these devices aren't 100% precise, they generally provide reliable readings that are enough for effective diabetes management.

Accuracy of standard blood glucose meters (BGMs)

According to the FDA and ISO guidelines, BGMs should provide results within ±15% of the lab-measured glucose value for most readings and ±20% in some cases. If your blood sugar level is 100 mg/dL, the meter should read between 85–115 mg/dL.[5]

Some factors can affect the accuracy of the device, such as:

• damaged or expired test strips
• insufficient blood samples  
• environmental conditions (e.g., extreme temperatures) 

Accuracy of continuous glucose monitors (CGMs)

CGMs measure glucose in the interstitial fluid, which may cause a slight delay in readings compared to blood sugar levels, especially during rapid changes like after meals or exercise.

However, newer CGMs like the Dexcom G7 and Freestyle Libre 3 have a Mean Absolute Relative Difference (MARD) of about 8-10%, considered accurate for real-time glucose tracking.

MARD shows, on average, how much a set of values differs from the true value relative to the true value's size.

Some factors, such as proper sensor placement and calibration, might affect accuracy.

How to measure the accuracy of your glucometer

• Test your glucose meter simultaneously as a lab blood test; its readings should fall within ±15% of the lab results.
• Use a control solution, which is typically included with the meter, to ensure the accuracy of the device and test strips.
• Measure your blood sugar twice a row to check if the readings are almost the same.
• If you find inaccuracy in your device, take it to your doctor’s office and compare its readings with professional equipment.

Factors to consider when choosing a blood glucose meter

Here are factors to consider when choosing a blood glucose meter:

• Look for a meter that fulfills international accuracy standards and has good reviews or professional recommendations.
• Choose a device with a simple display and clear instructions.
• Consider the price of the meter and the ongoing expense of test strips and lancets.
• Opt for a meter with data tracking and storage, as it helps to share results with your doctor.
• Look for a lightweight model with a durable carrying case.
• Advanced features like fast results or alternative site testing can be helpful.
• Consider using meters connected with smartphones or insulin pumps for better diabetes management.

Things to be aware of when using glucometers

Here are things to keep in mind when using glucometers:

1. Test your blood sugar levels at recommended times, such as before or after eating, for accurate readings.
2. Carefully follow the instructions provided by the manufacturer in the leaflet to ensure its proper use.
3. Regularly check the expiration dates on test strips and control solutions, as expired supplies can affect accuracy.
4. Store your glucometer and test strips in a cool and dry place.
5. Wash and dry your hands thoroughly before testing to prevent blood sample contamination.
6. Do not share lancets or lancing devices, as they can spread infections.
7. Some meters require calibration regularly, so follow the manufacturer’s instructions.
8. Remember that alternative testing sites, like the forearm or palm, may give different results than fingertip testing, especially during rapid blood sugar changes.
9. If the device displays error messages on the meter, follow the user manual to resolve the issue.

Wrap up

Blood glucose meters and continuous glucose monitors are useful tools for tracking diabetes and keeping blood sugar levels within a healthy range. These devices can help people understand how their daily food, exercise, and medications affect their blood sugar, making it easier to make good health decisions.

To get accurate readings, it’s essential to use them properly, such as testing at the right times, using fresh supplies, and storing the devices correctly.