Recently, continuous glucose monitors, a.k.a. CGMs, have been getting a lot of attention.
That’s because this past spring the wearable sensors, which send real-time glucose readings to an app on your phone, were approved by the US Food and Drug Administration to be sold over-the-counter in the US without a prescription.
While CGMs have been available in Canada without a prescription for a number of years, the FDA ruling means their use is now getting increased coverage in mainstream and medical media for use by people both with and without diabetes.
Even used by Olympic athletes
In fact, the devices were recently profiled around potential use with athletes during the Olympic Games in France. Reportedly, some endurance athletes are using CGMs as wearable trackers to monitor their glucose energy usage during training.
As one commentator noted, CGMs provide athletes with real-time glucose levels “so athletes never have to ‘bonk’ again.” (Bonking is the slang for the debilitating state in an endurance activity, also called "hitting the wall" , when the body’s glycogen stores are depleted, and the athlete’s muscles have no more fast-burning fuel to function.)
CGMs were originally developed as a tool to help people with type 1 diabetes manage their glucose levels, especially to avoid dangerous blood sugar lows. The devices eased the complicated calculations over carbohydrate counts and resulting insulin dosages, meeting a life-saving need.
Then CGM use expanded to people with type 2 diabetes, at first mostly for those needing insulin injections, then to anyone with the diagnosis. Now they have become available to those with prediabetes and anyone else who wants to try one to get more information on what their blood glucose is doing 24 hours a day.
"An incredibly helpful tool'
“CGMs can be an incredibly helpful tool for people to learn about how certain foods and activities can impact their blood glucose levels,” said Dr. Leanne Reimche, the chief medical officer of the Institute for Personalized Therapeutic Nutrition, which sponsors this remission site.
“I think they can give valuable information to people with prediabetes and type 2 diabetes. Some patients find it motivating to use this data to help make nutrition/lifestyle choices," she said.
Dr. Reimche also notes that CGMs, used by people who still take glucose-lowering medications, can also help monitor for episodes of hypoglycemia (very low blood sugar) in those who make large dietary changes, such as cutting out highly processed food and sugar.
“And as a physician, I also find it helpful to see the patient’s estimated A1c from their CGM in the clinic when we do not have a recent A1c in the lab,” she said.
“I love using a CGM,” said Elisabeth Westlake, who we have been following on this site each month as she puts her recent diagnosis of type 2 diabetes into remission by changing what she eats. “It gives me immediate feedback about what foods spike my blood sugar and what foods provide more stable and gentle rises and falls. I was able to drop my A1c from 6.4% to 5.7% on the meter by just noting those impacts and changing what I eat.”
So, should you consider trying one out? Here’s some information to consider.
First, how do they work?
Unlike a blood glucose metre, where you must prick your finger to test a drop of blood for your glucose levels, the CGM sensor is affixed to the back of your arm (or sometimes abdomen) where a hair-thin filament constantly measures glucose levels in the interstitial fluid (fluid in the space between your cells.)
The transmitter in the sensor then sends the readings to an app on your smartphone to give you automatic real-time readings any time night or day. Because the reading is from the interstitial fluid there is a slight lag (10 or 15 minutes) in the glucose results compared to a test of a drop of blood.
How much do they cost and how long do they last?
Usually, the app for your phone is free, but the average cost for each sensor is about $100 to $130 CDN. The sensor lasts approximately 14 days.
While someone with type 1 diabetes would use one for life, people with type 2 diabetes or prediabetes often only need to use one for a few weeks or months to get a good handle on their daily glucose patterns and how to improve them by diet and exercise.
Some extended benefits plans will cover the cost if it has been prescribed by your doctor to help manage your diabetes.
Where do you get a CGM?
Ask your pharmacist for one from behind the counter at your local pharmacy.
The two popular brands in Canada are the Freestyle Libre 2 and the Dexcom G7. (Medtronic also makes CGMs but they are integrated with an insulin pump and used primarily by insulin-dependent adults and children with type 1 diabetes.)
It is expected more CGM sensors will be coming on the market soon, such as a feature in smart watches and other wearable technology.
How do you apply the sensor?
Each brand of CGM sensor comes with specific instructions and an applicator device.
Typically, you clean the location (i.e., the back of your arm) with an alcohol wipe, apply the applicator to the area and push. You will feel pressure but usually no pain as the sensor filament goes into your skin and the sensor is attached with an adhesive on top of your skin.
It usually takes about an hour for the sensor to calibrate and then it will provide continuous readings either automatically or by touching your phone to the sensor.
How do you eat after you apply the sensor?
To get the most out of the possible lessons from your CGM, for the first few days of wearing one don’t change anything about your diet, sleep or exercise routine. You will learn so much by watching what happens to your glucose levels by your typical meals and activities. For example, you will see how a breakfast of a bagel and cereal affects your blood glucose compared to a bowl of Greek yogurt and berries. Or, how a restless night of poor sleep or a stressful day at work can cause glucose levels to rise.
After monitoring your typical daily glucose patterns without making changes for three or four days, then try some simple diet and exercise changes, as recommended on this site. For example, prioritize protein at every meal, reduce or eliminate your intake of sugar or ultra-processed foods, eat plenty of leafy green vegetables and try adding a walk around the block after each meal. What happens to your glucose measurements?
What are the main benefits of wearing a CGM?
The main benefits of wearing a CGM are:
An improved understanding of how certain foods and activities impact your glucose levels.
An improved motivation to manage or change your diet and engage in self-care activities to reduce your blood sugar.
A reduced need to prick your finger to test a drop of blood.
An ability to share your readings and trends with your health provider, to better manage your care, medications and overall metabolic health.
What are some cons of wearing a CGM?
Criticisms and cautions around the use of CGMs generally fall into five main categories:
The constant flow of information about glucose levels could be overwhelming for some people or incite unnecessary fear or stress.
The use of the CGM could trigger obsessions or eating disorders in some susceptible people.
Normal swings in glucose levels, such as rises during intense exercise (which comes from the liver making glucose to meet extra energy needs) could potentially lead people to stop exercising or pathologize normal bodily processes.
They are expensive and only last two weeks.
The use of CGMs by healthy people without diabetes, but who are curious about their bodily processes, has never been studied and so the actual effectiveness, or potential harm, is not known.
Where to find more information
A number of research studies as well as medical commentators have written about or produced videos on the use of CGMs. These resources cover people with type 2 diabetes and those who have prediabetes or are healthy but curious about their daily blood sugar patterns.
Here are some links to reputable sources for more information:
US National Institute of Health National Institute of Diabetes and Digestive and Kidney Diseases (NIDDKD) CGM information sheet
Cleveland Clinic CGM information sheet
Association of Diabetes Care and Education Specialists: pros and cons of CGMs
Nick Norwitz,Phd video on pros and cons on CGM use in general public
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