Diabetes Technology/ Continuous Glucose Monitoring (CGM)

Diabetes management has undergone a major shift in recent years. With growing awareness, rising prevalence of diabetes worldwide, and the need for tighter glucose control, technology has emerged as a critical partner in day-to-day care. For many individuals, especially those using insulin, traditional methods like occasional finger-prick blood tests no longer provide the level of insight needed to make timely and informed decisions.

This is where diabetes technology has stepped in, offering smarter, more responsive tools that help patients take control of their health with greater precision and confidence. One of the most significant advances is Continuous Glucose Monitoring (CGM), which allows real-time tracking of glucose levels throughout the day and night. Unlike standard glucose meters that give single-point readings (blood sugar levels 3 or 4 times/day), CGM systems reveal trends, fluctuations, and patterns that are often missed, which helps ensure proactive adjustments in diet, activity, or medication.

What is Continuous Glucose Monitoring (CGM)?

Continuous Glucose Monitoring (CGM) is a method used to track glucose levels continuously throughout the day and night. Unlike traditional blood glucose meters that provide a single reading at a given moment, CGM offers a continuous stream of data and captures how glucose levels change over time. This enables a more comprehensive understanding of glucose patterns, rather than isolated measurements.

CGM plays an important role in modern diabetes management, particularly for individuals who require close monitoring, such as those with type 1 diabetes, insulin-treated type 2 diabetes, or frequent episodes of hypoglycaemia. It helps identify periods of high or low glucose that may not be picked up by conventional testing, including nocturnal hypoglycaemia (low sugar levels overnight) or post-meal glucose spikes and provides valuable context for making adjustments to treatment, diet, or activity.

By shifting the focus from reactive testing to proactive monitoring, CGM supports better decision-making and more consistent glucose control, which helps minimise the risk of diabetes-related complications and fits in with preventative care rather than sick care (preventing complications rather than treating after complications have occurred).

How does CGM work?

Continuous Glucose Monitoring systems are designed to provide real-time insight into glucose levels without the need for constant finger-prick tests. They measure glucose in the interstitial fluid, the fluid surrounding the body’s cells, and deliver continuous updates to help users and healthcare providers make timely and informed decisions.

A typical CGM system involves the following components and processes:

• Sensor — a small, flexible sensor is inserted just beneath the skin, commonly on the upper arm or abdomen. It continuously detects glucose levels in the interstitial fluid.

• Transmitter — attached to the sensor, the transmitter sends the collected glucose data wirelessly to a compatible device.

• Display device — glucose readings are shown on a separate receiver, insulin pump, or smartphone app. Users can view real-time values, trend arrows, and graphs showing changes over time. Most individuals choose to use a smartphone as this also allows wireless transmission of this data to the clinics. 

• Alerts and alarms — most CGMs have built-in notifications to alert users when glucose levels are rising or falling too quickly or entering a dangerous range.

• Data tracking — the system stores historical data that can be reviewed during consultations, supporting more accurate adjustments to insulin, diet, or activity.

• Sensor lifespan — depending on the device, sensors are worn for 7 to 14 days before needing replacement. Many are water-resistant and discreet for ease of use in daily life.

This combination of components makes CGM a valuable tool for improving safety, enhancing glucose control, and supporting more responsive diabetes care.

Who can benefit from CGM?

Continuous Glucose Monitoring is especially beneficial for individuals who require close and consistent monitoring of their glucose levels but its usefulness extends beyond those with complex diabetes needs.

Those who may benefit most from CGM include:

• People with type 1 diabetes — CGM offers essential support for managing glucose fluctuations, detecting hypoglycaemia early, and adjusting insulin doses in real time.

• People with insulin-treated type 2 diabetes — for those on multiple daily injections or insulin pumps, CGM helps optimise control and reduce glucose variability.

• Children and adolescents with diabetes — CGM provides peace of mind for families by offering around-the-clock monitoring and alerts, including during sleep or school hours.

• Pregnant women with gestational diabetes or pre-existing diabetes — CGM supports tighter glucose control during pregnancy, which is crucial for both maternal and foetal health.

• Individuals with frequent or unrecognised hypoglycaemia — CGM helps detect sudden drops in glucose that may not present with obvious symptoms, enhancing safety and confidence.

• Older adults or those with impaired hypoglycaemia awareness — by alerting users to low glucose levels, CGM can help reduce the risk of dangerous events, particularly for those living alone.

• Active individuals managing diabetes — athletes and those with variable daily routines can benefit from the ability to monitor glucose in relation to physical activity, meals, and stress.

Even for people not on insulin, CGM may be used to identify glucose trends and support lifestyle or medication adjustments. When interpreted with professional guidance, CGM can be a powerful tool in personalising diabetes care.

How is a CGM sensor inserted and worn?

CGM sensors are designed to be discreet, minimally invasive, and easy to use in everyday life. Understanding how they are placed and worn helps users feel more confident and comfortable with the process.

• Sensor placement — the sensor is a small, flexible filament inserted just beneath the skin, most commonly on the upper arm or abdomen. Insertion is done using an automated applicator device and is typically quick and relatively painless. It’s easy enough to be done by the patient themselves. 

• Duration of wear — depending on the brand, sensors are worn continuously for 7 to 14 days before needing replacement. 

• User comfort — once inserted, the sensor is secured with adhesive and sits flat against the skin. Most users find it easy to wear under clothing, with little to no interference in daily activities, including sleep, work, and exercise. Many CGMs are also water-resistant, so they allow for showering and limited water exposure.

This combination of ease, comfort, and convenience makes CGM suitable for long-term use in both adults and children.

What are the advantages of using CGM over traditional glucose monitoring?

Traditional finger-prick testing provides only isolated glucose readings and often misses important fluctuations throughout the day. Continuous Glucose Monitoring (CGM), by contrast, offers a more detailed and responsive approach to diabetes care. Below are the key benefits of CGM systems:

• Real-time visibility — CGM tracks glucose levels continuously, updating readings every few minutes and showing not just the current value but also the direction and speed of change.

• Proactive alerts — built-in alarms notify users of impending highs or lows, allowing for timely intervention before symptoms become dangerous.

• Pattern recognition — by capturing data throughout the day and night, CGM reveals how glucose responds to meals, activity, stress, and sleep, helping users make better-informed decisions.

• Reduced finger-pricks — most CGM systems require minimal or no routine finger-prick testing, which makes them a comfortable and convenient device for patients.

• Tailored treatment — the detailed data enables healthcare providers to personalise insulin dosing, medication schedules, and lifestyle advice more precisely.

• Improved glucose control — CGM use is linked to increased time in target range (usually defined by glucose between 3.9 mmol/l and 10 mmol/l), lower HbA1c, and fewer severe glucose swings.

• Peace of mind — around-the-clock monitoring provides reassurance, especially during sleep, physical activity, or for those with hypoglycaemia unawareness.

With these advantages, CGM transforms diabetes monitoring from a reactive task into a proactive and data-driven approach that supports long-term health.

What information does CGM provide to patients and doctors?

CGM offers far more than just a number; it provides a detailed picture of glucose behaviour over time, which helps ensure smarter and more individualised diabetes care.

• Time in range — one of the most valuable metrics from CGM is the percentage of time glucose levels stay within a target range,  between 3.9 and 10 mmol/L. This gives a clearer indication of daily control than a single HbA1c value.

• Trend graphs — CGM displays visual graphs that show how glucose levels rise and fall throughout the day and night. These help users understand the impact of meals, exercise, stress, and medication on glucose patterns.

• Glucose variability — CGM tracks fluctuations and stability of glucose levels over time. Identifying frequent swings between highs and lows is important in reducing the risk of complications and improving quality of life.

• Personalised insights — with continuous data available, both patients and doctors can make more informed decisions about insulin dosing, meal planning, activity levels, and medication adjustments.

By revealing patterns that finger-prick testing would likely miss, CGM supports a more tailored and responsive approach to diabetes management, which leads to better outcomes and increased patient confidence.

Is finger-prick testing still necessary when using a CGM?

While CGM significantly reduces the need for traditional finger-prick testing, there are still certain situations where a manual check may be recommended.

• Device requirements — some CGM models require occasional finger-prick calibrations to ensure accuracy, particularly during the initial sensor warm-up period or when readings appear inconsistent.

• Confirming unexpected readings — if your CGM reports a sudden high or low value that doesn’t match how you feel, a fingerstick can help confirm whether the reading is accurate before taking corrective action.

• During rapid glucose changes — CGM measures glucose in interstitial fluid, which may lag behind blood glucose levels during sudden shifts. In such cases, a finger-prick test may provide a more immediate snapshot.

• When treating hypoglycaemia — it’s often advisable to verify low readings with a finger-prick before treating, especially if symptoms are not present or if sensor readings seem unclear. Again this is because CGM has a delay in response to sugar correction. 

• Medical or procedural requirements — in some clinical settings or for driving safety certifications, traditional blood glucose readings may still be required as official documentation.

For many users, the number of finger-pricks drops dramatically after switching to CGM but understanding when to check manually helps ensure safe and accurate diabetes management.

Are there any limitations to using CGM?

Although Continuous Glucose Monitoring offers many benefits, it is important to be aware of its limitations so users can manage expectations and use the technology safely and effectively.

• Sensor accuracy — while CGMs are generally reliable, readings can occasionally differ from finger-prick blood glucose results, especially during rapid glucose changes or in the first 24 hours after sensor insertion.

• Lag time — CGMs measure glucose in interstitial fluid, not directly from the blood. This can lead to a slight delay, usually around 5 to 10 minutes, particularly noticeable during sudden rises or drops in glucose levels.

• Sensor wear and replacement — most sensors need to be replaced every 7 to 14 days, depending on the brand. Improper insertion or sensor dislodgement can also affect performance.

• Skin irritation — some users may experience redness, itching, or sensitivity at the sensor site, especially with prolonged or repeated use.

• Medication interference — certain medications and supplements can affect sensor accuracy. These include paracetamol (acetaminophen), vitamin C, and hydroxyurea. These substances may cause the sensor to report glucose levels as higher or lower than they truly are. 

• Cost and accessibility — CGMs can be expensive, and not all devices are fully subsidised. This may limit access for some patients, particularly those without private insurance coverage. Thankfully costs have come down recently and for most this technology is accessible

• Learning curve — it can take time to understand how to interpret trend arrows, alerts, and data reports. Without proper guidance, users may feel overwhelmed by the volume of information.

• Technical issues — like all electronic devices, CGMs are subject to occasional glitches, signal loss, or transmitter failures, which may interrupt monitoring temporarily.

Being aware of these limitations allows users to take full advantage of CGM technology while also using finger-prick testing or professional advice when needed.

How do I choose the right CGM device for me?

Choosing a CGM device depends on your individual needs, lifestyle, and medical requirements. At The Metabolic Clinic we can help recommend CGM systems with a proven track and ease of use. 

• Accuracy and reliability — look for devices that have a strong track record of consistent and accurate readings, especially during periods of rapid glucose change or at night.

• Calibration requirements — some CGMs require occasional finger-prick tests for calibration, while others are factory-calibrated and do not need manual input. If convenience is a priority, a no-calibration system may be preferable.

• Smartphone and device compatibility — many CGMs sync with smartphones or smartwatches via Bluetooth. Make sure the system you choose is compatible with your phone’s operating system and supports the app features you require.

• Sensor wear time — different devices offer varying durations of wear, from 7 to 14 days or longer. Consider how frequently you are comfortable changing sensors and whether extended-wear models are appropriate.

• Alerts and customisation — some systems allow you to set personalised alerts for high or low glucose levels, while others may be more basic. Choose a device that matches your preferences for notifications and discretion.

• Integration with insulin pumps — if you use an insulin pump or plan to in future, selecting a CGM that integrates with your pump can help streamline your management through hybrid closed-loop technology.

• Cost and insurance coverage — prices vary between models, and not all CGMs are subsidised or covered by private insurance. Check with your healthcare provider or insurer to understand your coverage options.

Discussing these considerations with your doctor or diabetes care team can help you select a CGM that fits both your clinical needs and lifestyle.

Summary 

Continuous Glucose Monitoring (CGM) has become a cornerstone of modern diabetes care, moving beyond the limitations of finger-prick testing to provide continuous, real-time data. By capturing fluctuations, trends, and time spent in target range, CGM offers valuable insights that support more precise adjustments to treatment, diet, and lifestyle. 

Its benefits include improved safety through alerts, greater convenience, and enhanced personalisation of care for people with type 1 diabetes, insulin-treated type 2 diabetes, gestational diabetes, and those prone to hypoglycaemia. Although CGM has limitations, such as sensor replacement, cost, and occasional accuracy issues, it remains a powerful tool in achieving better long-term glucose control. 

If you are interested in learning how CGM can support your diabetes management, schedule a consultation with us for more information and advice on whether CGM can help you.    

Frequently Asked Questions (FAQs)