Continuous and flash glucose monitoring allows you to check your blood sugar levels without pricking your finger. They both rely on a small sensor placed under the skin to read the sugar levels at any time of the day or night.

The data from the sensor is then transmitted to a mobile device or any other device it is compatible with. With the CGM or flash glucose monitors, you can set the alarm to go off anytime the sugar levels go too low or above the target ranges. Read on to learn the main differences between flash and continuous glucose monitoring.

What Is A Flash Glucose Monitoring System?

A flash glucose system is also called intermittent continuous glucose monitoring or iCGM. The system uses a wired glucose oxidase enzyme co-immobilized on an electrochemical sensor implanted on the arm for 14 days.

The sensor is the size of a coin and has a short filament inserted into the upper arm’s subcutaneous tissue. A flash glucose system does not need calibration with a patient’s SMBG, but the availability of the glucose data is only on demand.

A flash glucose system does not continuously show the glucose values in the interstitial fluid but only shows it once you place a reader near a sensor. The data is transferred from the sensor to the chosen reader and recorded automatically every 15 minutes.

The blood sugar levels can be downloaded anytime and represented in the Ambulatory Glucose Profile (AGP). The system then combines the data from the sensor over 14 days, which can then be summarized to give a visual display of the glycemic patterns.

What Is A CGM System?

Continuous glucose monitoring systems show blood glucose levels in real-time. They have proven to be beneficial for patients diagnosed with type 1 diabetes. A CGM system is programmed to record blood glucose levels every 1 to 5 minutes and their rate of change.

It is characterized by a ‘lag time’ between the interstitial fluid and the plasma, meaning the interstitial glucose values do not always match the blood glucose values. To maintain accurate readings, the system requires daily calibration, usually twice daily.

At this time, only the Dexcom G6 system does not require calibrations. All the other models in the market require you to calibrate the system daily. A CGM system also has an alarm that goes off whenever the glucose values are too low or above the target range.

What Are The Differences Between Flash Glucose Monitoring And CGM?

CGM and FGM have many similarities and are all used to help manage diabetes with their sensors that provide real-time blood glucose readings. But how do you know which one to choose? Here are the main differences between the two to help you make an informed decision.

Manual Vs. Automatic Scanning

CGM requires the list effort since it automatically records blood sugar levels at the programmed intervals while producing readings. In contrast, FGM is more on the manual side since you need to scan the sensor under the arm to get the readings.

Compatibility With Insulin Pumps

Some people diagnosed with diabetes use an insulin pump attached to their bodies to deliver small amounts of insulin throughout the day and night rather than injecting it yourself. An insulin pump is designed to help you keep your blood sugar levels in the target range.

If you use an insulin pump, you must use a glucose monitor that is compatible with an insulin pump and can alter insulin doses based on blood sugar levels. A flash glucose monitor, on the other hand, does not.

SystemGlucose MeasurementUser CalibrationData DisplayTrend ArrowsAlarms in Case of Hypoglycaemia or HyperglycaemiaMaximum Duration of SensorCan be connected to an Insulin PumpAdjustment of the Insulin Dose Based on Sensor Results
FGMInterstitialNoon demandYesNo14 daysNoNo
CGMInterstitialYes, daily (except for Dexcom G6)displayed automaticallyYesYesDepending on the kindYesYes (presently, only Dexcom G5 and G6)


Whether you choose an FGM or a CGM to help you manage diabetes depends on your preference, lifestyle, whether or not you use an insulin pump, how often you would want to prick your finger, and where you want to wear the sensor. However, both work similarly to help you control your diabetes

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