Are continuous blood glucose monitors (CGM) worth the hype?

Initially developed for use by people with diabetes, continuous blood glucose monitors (CGMs) are now being adopted by an increasing number of individuals who proudly wear this small device on their arms. 

What are continuous blood glucose monitors?

A CGM is composed of a “sticky part” containing the device that processes the information provided by the small needle attached to the bottom, which communicates it to an app. 

Contrary to common belief, the needle is not inserted into a blood vessel but instead measures the glucose concentration in cellular interstitial fluids, estimating the glucose concentration in blood via an algorithm. The data stream is continuous, providing graphics showing blood sugar highs and lows throughout the day and night. 

How does it differ from other blood glucose measuring devices?

More traditional tools, such as glucose meters, measure sugar levels in blood which is obtained by poking your fingertip and letting a drop fall into the meter strip. Blood tests, such as HbA1c, are used to understand the average levels of blood glucose over a month, analysing how “damaged” red blood cells are by high sugar levels. GCMs offer real-time data, providing a curve of sugar highs and lows for the 24 hours of the day.

What are the pros and cons?

Pros:

• Easy to wear and painless, as there is no need to draw blood either at the GP surgery or with the glucose meter tool.
• Offers a picture of what is happening during the day, highlighting hyper or hypoglycaemic episodes and fluctuations in blood sugar levels.
• Has an alarm system to alert of hypoglycaemic episodes.
• Connected to an app, so it is easy to retain and store data for your healthcare professional to check.

Cons:

• Not as accurate as it doesn’t measure actual blood sugar levels, but it estimates them via an algorithm upon the glucose levels of interstitial cellular fluids. 
• CGMs were designed and calibrated for people with diabetes, so they might be even less accurate for the general population.
• It might lead to incorrect evaluations around food, for example, you might see a big spike after eating raspberries and decide to cut them out, while they might not be the problem, as the data is just an estimate.
• It can lead to excessive checking and fixation around food, obsessing on individual readings and not on long-term patterns.
• It can be quite expensive.

Are they worth the investment?

GCMs can be very useful for diabetic and pre-diabetic individuals as a monitoring tool, especially as they warn about hypoglycemia and show the trend of blood glucose fluctuations throughout the day without the need for constantly pricking your fingers to obtain a reading with a glucose meter.

For health-conscious individuals, it can be an interesting tool to have, as it provides more metrics to draft a personalised nutrition plan, for example, to spot significant glucose drops mid-afternoon that lead to carb cravings. It can be considered a learning tool for action changes, but it should not be taken too literally or used to eliminate food groups because they “spike”.

In my own practice, I use it with diabetics and pre-diabetics, as the data provided helps them stay on track with their plan and supports their motivation in making changes and implementing new habits.

I do recommend it for two weeks to patients who approach me regarding fatigue, cravings or if I suspect that blood sugar levels are altered in order to see if blood glucose dysregulation and sharp fluctuation might be the cause.

I have also tried it on myself, and I have found it interesting, but I won’t be wearing it constantly, as I believe it won’t provide me with the information I need to optimise my health.

It is a valid tool, but I recommend consulting with a healthcare professional before interpreting the data on your own, as an expert can help you understand what it really means and what actions (if any) should be taken to address any anomalies spotted by the CGM.