Your Guide to CGM-Continuous Glucose Monitoring at Home

Awareness often brings about responsibility and action. And that’s the basis for managing diabetes. Healthcare professionals swear by the power of data at hand to make meaningful decisions for their patients, and with technology at their fingertips today; this has become very helpful in managing diabetes and preventing diabetes complications.

Self-monitoring of glucose has been actively advocated by all international guidelines for enabling diabetes control. This can be achieved in two ways: using a blood glucose monitor and, more recently, continuous glucose monitoring.

In this article, we will understand the need, the underlying concept, benefits as well as drawbacks of continuous glucose monitoring in type 2 diabetes. We will also identify the people who will benefit most from CGM.

Continuous Glucose Monitoring: Making sense of blood sugar levels

Traditionally glucometers have been routinely used for monitoring blood sugar levels. They are economical, easy to use, and they give results that coincide well with blood tests taken in a laboratory.  

They provide useful data on the level of blood sugar levels at the moment the test is done. This awareness helps people with diabetes stay on track with their diet, physical activity, and medications. However, using blood glucometers may have some disadvantages:

• They require multiple pricks during the day to draw blood for the fingerstick used for measuring blood sugar levels.
• They are not indicative of future events, such as an increase or decrease in blood sugar levels.
• They may not give accurate levels as they are likely to be affected by the environment in which the test is done, such as the level of oxygen, temperature and the presence of interfering factors, such as the number of red blood cells in the blood.  
• They may be inconvenient and aesthetically unfavourable for people on-the-go.  

Another test routinely used to monitor blood sugar levels is glycated haemoglobin or Hba1C. This useful parameter gives the bigger picture of the average blood sugar levels in the past 3 months. HbA1c is not altered by exercise or diet and is a simple test involving a blood sample.  

While HbA1c is the most reliable measure used by healthcare professionals worldwide and also recommended by international guidelines for the management of diabetes, HbA1c also has certain drawbacks as a measure of glucose control.

Normally blood sugar levels undergo fluctuations depending upon the time of the day, the food ingested, any medications taken, or exercise done. These fluctuations may be amplified in people with diabetes. So, while HbA1c gives useful data on the overall control of diabetes, it does not record or foresee these fluctuations as it does not let us know of any highs or lows in the blood sugar levels that may have happened during that period.

The advent of continuous glucose monitoring has addressed several of these issues that one may face with glucometers or HbA1c testing. It also provides additional data that can help the healthcare professional, or the caregiver make timely decisions with respect to diet, exercise and medication.

Understanding CGM

Unlike glucometers that require the fingertip to be pricked to draw blood and measure it using a fingerstick, CGM normally has a sensor placed under the skin in the back of the arm or the abdomen.  

This sensor will continuously measure the sugar levels in the fluid below the skin. This data is then transmitted to a receiver and analysed.  

Thus, CGM helps continuously measure blood sugar levels 24 hours a day, even while sleeping, exercising, or swimming.

The Time-in-range concept of CGM

International guidelines recommend that people with diabetes should have their blood sugar levels in the range of 70mg/dL to 180mg/dL at least 70% of the time during the day.  

The less time spent in this range, the higher the likelihood of the HbA1c being above 7% and the greater the risk of developing diabetes-related complications.

E.g., a time-in-range of 50% corresponds to an HbA1c of 8%.

With CGM, it is possible to measure the amount of time spent within this range by a person with diabetes and take necessary actions to reduce the time spent out-of-range.

Benefits of CGM

Ensuring continuous monitoring of blood sugar levels has multiple benefits:

• Better sense of numbers: By using CGM, one understands the blood sugar levels at any given time and the past and predictive future levels. This is because CGM can forecast the future direction of blood sugar levels based on past trends.
• Predictive alarms: CGMs can be set up to provide alarms whenever the blood sugar levels go beyond a pre-decided level. This can help people with diabetes, or their caregivers be aware of low or high blood sugar levels and take the necessary action.  
• Time spent in the range: By measuring the time in range spent by a person with diabetes, CGM can help reduce the risk of diabetes-related complications.
• Identifying the signs of low blood sugar levels: Many people with type 2 diabetes cannot identify the signs of low blood sugar levels (hypoglycemia), which can be life-threatening. CGM allows better recognition of an episode of low blood sugar level and predicts it well in advance to help take timely corrective action.
• Sharing of data: Many CGM devices allow sharing of data with the physician or a caregiver enabling easy access to data, continuous monitoring, and timely interventions.
• Convenience: Prevents multiple pricks.

Drawbacks of CGM

• CGM devices can be expensive.
• A certain level of technical understanding is required to best use CGM.
• Some CGM devices require sensors to be scanned often to protect the data, which can be inconvenient.
• Contact of the CGM device with the skin can cause allergic reactions.

People with diabetes best suited for CGM

Certain groups of people with diabetes will benefit more from CGM:

• Type 1 or type 2 diabetes patients on insulin or insulin pumps.
• People with diabetes who are prone to low blood sugar but have difficulty recognising its signs and symptoms.
• People with diabetes switching to a new type of insulin or an insulin pump for the first time.
• People who tend to have a wide variation in glucose levels during the day.
• People who like to be more informed about their blood sugar levels.

Conclusion

Continuous glucose monitoring is a useful tool not only for understanding blood sugar levels but also for making informed, timely decisions on medical and lifestyle interventions to keep diabetes under control. With the use of technology, important data on blood sugar levels can be shared with healthcare professionals and caregivers and help prevent episodes of low blood sugar levels and the risk of diabetes-related complications.