Continuous blood glucose meter (CGM)

What is a continuous blood glucose meter (CGM)?

CGM is an abbreviation for Continuous Glucose Monitor, which is a device that measures blood sugar levels continuously and helps to manage blood sugar.

With a normal glucose monitor, it is difficult to identify a trend and frequent blood tests are required, which is not as helpful in managing blood sugar levels.

With a cgm, blood sugar levels and trends can be seen in real time, so it is easier to cope with hypoglycemia and hyperglycemia in advance. It can also help to reduce the ups and downs of blood sugar, as trends can be identified earlier. This allows for blood sugar management at a more constant level and trend.

Components of a CGM

The Sensor

The sensor is a component that sits on the skin, with a small string inserted into the skin via a needle.

It measures blood sugar levels through the interstitial fluid between the cells.

The Transmitter

The transmitter is responsible for sending the blood sugar levels measured by the sensor at regular intervals.

For most cgms, the transmitter and the sensor are a set that need to be used together.

The Receiver

The receiver is a component that reads the blood sugar levels sent by the transmitter and displays the value to the user.

These days, it is also possible to install an app on a smartphone or smartwatch and use them as a receiver.

Wearing a CGM

As the CGM measures the glucose levels in the interstitial fluid instead of in the blood, there is a delay of 5 to 15 minutes in blood sugar levels compared to measuring directly via blood drops. A recent advanced correction algorithm however can measure the levels close to real-time blood sugar values.

The transmitter sends blood sugar levels measured by the sensor every 5 minutes to the receiver.

Why should I wear CGM?

Diabetes is a life-threatening chronic disease that requires constant treatment and self-management training.

Blood sugar levels are affected by lifestyle, food, general condition and exercise, which can cause blood sugar levels to change often. (Diabetics also often have higher blood sugar levels than non-diabetics)

For many diabetics, more than 70% of their blood sugar levels are outside the recommended normal blood sugar range (80-140 mg/dL), however these devices make it easier to manage blood sugar levels and to stay within the normal range.

Discrete blood sugar measurement (also referred to as SMBG: Self Monitoring of Blood Glucose) can leave the user at a disadvantage, because it is difficult to judge the blood sugar trend and how external factors affect blood sugar. (For blood sugar management, the direction or speed of blood sugar changes are more important than the actual blood sugar level itself.)

Frequent blood sugar measurements and monitoring are necessary, but there is a limited number of measurements obtained via traditional finger stick methods.

The accuracy of CGMs has vastly improved compared to when they first came onto the market, and the price is getting more affordable as well.

Useful tips for wearing a CGM

Calibration of your cgm should be done when the blood sugar level is relatively even (when there is less than 10mg/dL fluctuation within 5 minutes).

If there is pressure on the sensor area, the interstitial fluid is pushed away and it may register as hypoglycemia, so if there is a sudden low level, check the sensor area first.

The sensor may be inaccurate when displaying low or high blood sugar levels, so it is recommended to double check via finger stick before treatment.

It is better to attach a new sensor during the day rather than at night.

There may be a delay of 5 to 15 minutes compared to the actual blood sugar level, so if the blood sugar trend is rapidly changing, remember the delay as well and double check.

Although more blood tests and injections are needed to check your blood sugar levels compared to using SMBG, you can see a moderate blood sugar trend and reduce blood sugar spikes caused by overcorrection of low blood sugar.