Continuous Glucose Monitors Explained: How CGM Works in 2026

A continuous glucose monitor (CGM) is a wearable device that measures glucose levels in the interstitial fluid every few minutes, providing real-time data and trends without routine fingersticks. CGMs help people with diabetes, prediabetes, and even athletes track how food, exercise, and stress affect blood sugar. In 2026, CGMs are smaller, more accurate, and more affordable than ever, with some models lasting up to 14 days. This guide explains what a CGM is, how it works, who benefits, and key factors to weigh before using one.

What Is a Continuous Glucose Monitor (CGM)?

A continuous glucose monitor (CGM) is a small wearable sensor that automatically measures glucose levels in the interstitial fluid—the fluid surrounding cells—every 1 to 5 minutes. It transmits that data wirelessly to a receiver, smartphone app, or insulin pump, giving you a continuous picture of your glucose trends. Unlike a traditional blood glucose meter that requires a fingerstick for a single reading, a CGM provides up to 288 readings per day, revealing patterns and fluctuations that a single test misses. According to the American Diabetes Association’s 2025 Standards of Care, CGMs are recommended for anyone on intensive insulin therapy and are increasingly used by people with type 2 diabetes and prediabetes.

How Does a CGM Work?

A CGM system has three main components: a sensor, a transmitter, and a display device.

The Sensor

The sensor is a thin, flexible filament inserted just under the skin, typically on the abdomen or upper arm. It measures glucose in the interstitial fluid using an enzyme-based electrochemical reaction. The sensor is worn for 7 to 14 days, depending on the brand, then replaced.

The Transmitter

The transmitter, either attached to the sensor or integrated into it, sends glucose data wirelessly to a display device via Bluetooth or a proprietary radio frequency. Some transmitters are rechargeable and last months; others are replaced with the sensor.

The Display Device

A display device can be a dedicated receiver, a smartphone app, or an insulin pump. It shows current glucose, trend arrows (indicating direction and speed of change), and graphs of glucose over time. Many apps also provide alerts for high or low glucose levels, which can be set to vibrate or sound.

Calibration and Accuracy

Most modern CGMs are factory-calibrated and do not require fingerstick calibration. However, if your CGM readings do not match how you feel or a fingerstick test, the FDA recommends confirming with a traditional meter before making treatment decisions. According to the FDA’s 2024 guidance on CGM accuracy, systems must meet a mean absolute relative difference (MARD) of under 15%—lower is better. In 2025, the FDA approved several next-generation sensors with MARD values around 8-9%.

Why CGMs Matter: Benefits Beyond Fingersticks

CGM use is associated with improved glycemic control and reduced risk of severe hypoglycemia. A 2024 meta-analysis by the Journal of Diabetes Science and Technology found that CGM users reduced their HbA1c by an average of 0.5% compared to self-monitoring blood glucose. Additionally, CGM data helps identify post-meal glucose spikes, which are linked to increased cardiovascular risk even in people without diabetes.

Who Should Use a CGM?

People with Type 1 Diabetes

For individuals with type 1 diabetes, CGM is a standard of care. The American Diabetes Association recommends CGM for all adults with type 1 diabetes who are on intensive insulin therapy. It reduces the burden of frequent fingersticks and provides alerts for dangerous lows.

People with Type 2 Diabetes

CGM is increasingly used by people with type 2 diabetes, especially those on insulin or at risk of hypoglycemia. A 2025 study in Diabetes Care showed that CGM use in type 2 diabetes led to a significant reduction in HbA1c and improved time-in-range.

People with Prediabetes or Metabolic Concerns

People with prediabetes or those interested in optimizing metabolic health may use CGMs to understand how diet and lifestyle affect glucose. While not medically necessary for everyone, CGMs can help identify glucose spikes from certain foods and guide healthier choices.

Athletes and Biohackers

Some athletes and health enthusiasts use CGMs to fine-tune nutrition and training. They monitor glucose during exercise to maintain performance and avoid crashes. However, the evidence for using CGMs in healthy athletes is still emerging; a 2023 review in Sports Medicine noted potential benefits but called for more research.

CGM vs. Traditional Blood Glucose Meters

Feature	CGM	Traditional Meter
Frequency	Every 1-5 minutes	Each fingerstick
Invasiveness	Sensor insertion every 7-14 days	Multiple fingersticks daily
Data	Continuous trends and patterns	Single snapshots
Alerts	High/low and trend alerts	None
Cost	Higher upfront cost; sensors ongoing	Lower cost per test
Accuracy	MARD typically 8-12%	MARD typically 5-10%
Wear time	7-14 days per sensor	Immediate

As the table shows, CGMs offer far more data and convenience but at a higher cost. For people who need frequent monitoring, the benefits often outweigh the expense.

What to Consider Before Getting a CGM

Cost and Insurance Coverage

CGMs are not cheap: sensors can cost $100-$300 per month without insurance. Many insurance plans cover CGMs for people with diabetes who meet certain criteria, such as insulin use or frequent hypoglycemia. According to the Centers for Medicare & Medicaid Services, Medicare covers CGMs for beneficiaries with diabetes who use insulin or have problematic hypoglycemia. Check your plan’s coverage before purchasing.

Accuracy and Sensor Placement

Accuracy varies by brand and sensor placement. The FDA requires that CGM systems meet accuracy standards, but individual results may differ. Rotate sensor sites to avoid skin irritation and follow manufacturer instructions for insertion. Some sensors are approved for the upper arm only; others allow abdomen or thigh placement.

Skin Irritation and Adhesion

Some people experience skin irritation from the adhesive or the sensor filament. If you have sensitive skin, look for hypoallergenic options or use barrier wipes. In 2025, several brands introduced extended-wear sensors with improved adhesives that reduce irritation.

Data Sharing and Integration

Most CGM apps allow you to share data with healthcare providers or family members in real time. This can be valuable for caregivers of children with diabetes. Also, consider whether the CGM integrates with your insulin pump or other devices. The interoperability standards set by the FDA in 2024 have made it easier to combine devices from different manufacturers.

How to Get a CGM

To get a CGM, you typically need a prescription from a healthcare provider. Your provider can help you choose a model based on your needs, lifestyle, and insurance coverage. Many diabetes clinics offer CGM training to help you get the most from the device. If you do not have diabetes but are interested in tracking your glucose, some companies offer direct-to-consumer programs, but these are not covered by insurance and may not be medically supervised.

Now That You Understand the Basics

You now know what a continuous glucose monitor is, how it works, and who benefits from it. If you are considering a CGM, talk to your doctor about whether it is right for you. For more details, explore our guides on how to choose a CGM and interpreting your glucose data.