Continuous glucose monitors, commonly called CGMs, have transformed the way many people understand and manage blood glucose. Originally developed for people with diabetes, CGMs are now increasingly marketed and used by people who do not have diabetes as a tool for improving nutrition, fitness, weight management, energy, and overall health.
From a dietitian’s perspective, this technology can be incredibly useful, but it is also important to understand what the numbers actually mean.
A CGM can provide valuable information about how food, physical activity, stress, sleep, medications, and other factors influence glucose levels. For someone with diabetes, these insights can help guide medication management and reduce the risk of dangerous highs and lows. For someone without diabetes, a CGM may provide interesting information about individual glucose patterns and responses to different foods.
However, more data does not automatically mean better health.
In fact, one of the biggest concerns I have as a dietitian is that people can become overly focused on achieving a particular glucose number rather than looking at the bigger picture of nutrition and health. A temporary rise in blood glucose after eating is a normal physiological response. A higher glucose reading after a meal does not automatically mean that the food was “bad,” unhealthy, or something that needs to be eliminated.
The goal should not be to create a perfectly flat glucose curve but rather to use glucose information appropriately, in context, and without losing sight of overall health.
What Is a CGM?
A continuous glucose monitor is a small wearable device that measures glucose levels in the fluid surrounding cells, called interstitial fluid. Most CGMs use a small sensor placed just under the skin, often on the back of the upper arm or abdomen, depending on the device.
The sensor collects glucose readings throughout the day and sends the information to a receiver, smartphone, or other compatible device. Instead of providing one isolated blood glucose measurement, a CGM can show patterns and trends over time.
This is particularly helpful because glucose is constantly changing.
For example, a person may see glucose rise after breakfast, gradually fall afterward, increase again during exercise, and change overnight. Rather than seeing one number at a time, a person can begin to see how different factors affect glucose throughout the day.
For people with diabetes, this information can be clinically meaningful. The American Diabetes Association’s 2026 Standards of Care recommend CGM for adults with diabetes who use insulin, use non-insulin medications that can cause hypoglycemia, or are using a diabetes treatment where CGM can assist with management.
CGM use has also expanded into populations without diabetes. Some people use short-term CGM trials to learn more about their individual responses to meals, exercise, sleep, or other lifestyle factors.
The important distinction is that the purpose and interpretation of CGM data are different depending on whether a person has diabetes.
How CGMs Help People With Diabetes
For people living with diabetes, CGM technology can provide information that traditional finger-stick testing cannot.
A finger-stick glucose test gives you a snapshot. A CGM can show a movie. That difference can be extremely valuable.
Someone taking insulin, for example, may need to understand not only whether glucose is high or low but also whether glucose is rapidly rising or falling. CGM information can help identify patterns of hyperglycemia, hypoglycemia, and glucose variability.
The American Diabetes Association recognizes several important CGM metrics, including:
- Time in range
- Time above range
- Time below range
- Mean glucose
- Glucose management indicator (GMI)
- Coefficient of variation
- Glucose trends and patterns
For many nonpregnant adults with diabetes, the commonly used time-in-range target is greater than 70% of readings between 70 and 180 mg/dL, although individual goals should be determined based on the person’s health status and treatment plan.
CGMs can also be particularly valuable for identifying hypoglycemia.
This can be especially important for people taking insulin or certain medications that increase the risk of low blood glucose. CGMs can alert users when glucose is dropping, potentially allowing them to respond before glucose becomes dangerously low.
For people with diabetes, CGM data can also help the health care team identify patterns that may not be obvious from occasional finger-stick measurements or an A1C alone.
For example, a person’s A1C might look acceptable while their CGM reveals significant glucose variability or frequent episodes of hypoglycemia.
This is one reason CGM and A1C should not be viewed as competing tools. They provide different types of information.
CGMs Can Help Connect Food with Glucose Patterns
One of the most useful aspects of CGM technology from a nutrition standpoint is its ability to demonstrate how food affects glucose.
After eating carbohydrates, glucose generally rises as carbohydrates are digested and absorbed. The size and duration of that increase can vary considerably from person to person.
Factors that can influence the response include:
- The amount of carbohydrate consumed
- The type of carbohydrate
- Fiber content
- Protein and fat in the meal
- Portion size
- Meal composition
- Physical activity
- Medications
- Stress
- Sleep
- Hydration
- Timing of the meal
- Individual insulin sensitivity
This can help move away from overly simplistic statements such as “carbohydrates are bad” or “this food spikes blood sugar.”
Instead, we can ask a better question: What happens when this person eats this food, in this amount, as part of this meal, under these circumstances?
That is a much more individualized approach to nutrition.
For example, someone might notice that eating a piece of fruit by itself produces a quicker glucose rise than eating the same fruit alongside Greek yogurt and nuts. Another person might see very little difference.
Neither response is necessarily “right” or “wrong”, it is simply information.
A dietitian can use that information to help the individual identify patterns that are practical and meaningful.
A Glucose Rise After Eating Is Not Automatically Bad
This is one of the most important concepts to understand when using a CGM.
Blood glucose is supposed to rise after eating.
Food provides energy, and carbohydrate containing foods are broken down into glucose and other molecules that the body uses for fuel. The body has sophisticated systems involving insulin, glucagon, the liver, muscles, and other tissues to regulate glucose.
Therefore, seeing glucose increase after a meal is not evidence that something has gone wrong.
Unfortunately, many people without diabetes begin using CGMs and become alarmed by normal post-meal increases.
They may see a glucose reading of 130, 140, or 150 mg/dL and assume they have caused metabolic damage. That interpretation is not supported simply by seeing a temporary rise on a CGM.
For someone without diabetes, a CGM should not be used as a diagnostic tool. The ADA states that there is currently insufficient evidence to support CGM as a method for screening for or diagnosing prediabetes or diabetes.
If someone is concerned about their risk of diabetes, the appropriate approach is to speak with a physician or qualified health care professional about validated diagnostic testing such as A1C, fasting plasma glucose, or an oral glucose tolerance test.
A CGM can provide information, but it does not replace appropriate medical testing.
What About CGMs for People Without Diabetes?
This is where the conversation becomes more complicated.
CGMs are increasingly being used by people without diabetes who want to improve their nutrition, lose weight, optimize athletic performance, improve energy, or simply learn more about their bodies.
There are potential benefits to this approach. A person may discover that eating a balanced breakfast helps them feel more energetic than skipping breakfast. Someone may notice that walking after a meal is associated with a smaller or shorter glucose rise. Another person may discover that inadequate sleep is associated with different glucose patterns. These observations can potentially increase awareness and motivation.
However, research involving CGM use in people without diabetes is still developing. A recent systematic review noted that CGMs may provide immediate feedback about diet and physical activity in healthy adults but also emphasized that evidence in non-diabetic populations remains limited and the impact on cardiovascular outcomes is unclear.
In other words, CGM use in people without diabetes is interesting, but it should not be oversold. We do not have enough evidence to say that every healthy person should wear a CGM, nor should we imply that using a CGM will automatically improve metabolic health.
The Risk of Becoming Afraid of Food
One of my biggest concerns with CGMs for people without diabetes is the possibility of creating unnecessary food fear.
Imagine someone eats a banana and notices a glucose increase. They may conclude:
“Bananas spike my blood sugar. I shouldn’t eat bananas.”
The problem is that the glucose response alone does not tell us whether the banana was a healthy choice. A banana provides carbohydrates, fiber, potassium, vitamin B6, and other nutrients. A rise in glucose after eating it is expected.
Similarly, a person may see a relatively small glucose response after eating a food that is not particularly nutrient-dense. That does not automatically make that food the healthier choice.
This is an important limitation of using glucose as the sole measure of nutritional quality. A food should not be judged only by what it does to blood glucose. Nutrition is much bigger than glucose.
We also need to consider:
- Protein
- Fiber
- Vitamins and minerals
- Essential fatty acids
- Phytochemicals
- Satiety
- Digestive health
- Bone health
- Cardiovascular health
- Food enjoyment
- Cultural preferences
- Accessibility
- Sustainability
- Overall dietary pattern
A diet consisting entirely of foods that produce minimal glucose fluctuations would not necessarily be a nutritionally complete or enjoyable diet.
Don’t Chase a Flat Glucose Curve
Social media has contributed to the idea that “optimal” health means keeping glucose as flat as possible. This is an oversimplification.
Healthy bodies are dynamic. Glucose changes in response to eating, exercise, hormones, stress, illness, and other physiological processes. A completely flat glucose curve is not the goal.
Trying to eliminate every glucose rise can also lead people toward unnecessarily restrictive eating patterns. For example, someone might begin avoiding fruit, whole grains, legumes, or other carbohydrate-containing foods because their CGM shows a post-meal rise.
From a dietitian’s perspective, that can be counterproductive.
Instead of asking, “How do I prevent my glucose from ever going up?” a better question is:
“What patterns support my health, and what does my glucose data tell me that is actually actionable?”
That shift in mindset is important.
Looking Beyond a Single Number
CGM data can be overwhelming. The app may display a number every few minutes, arrows showing trends, graphs, alerts, averages, and other statistics. It can be tempting to react to every change, but glucose is constantly moving.
One reading is rarely meaningful on its own. Instead, look for patterns.
For example:
- Does glucose consistently rise significantly after certain meals?
- Does it remain elevated for a prolonged period?
- Are there recurring overnight patterns?
- Does physical activity change your glucose response?
- Does lack of sleep appear to affect your glucose?
- Are there repeated episodes of low glucose?
- Do medication changes correspond with different patterns?
This is where professional interpretation becomes valuable. A dietitian can help separate useful information from noise.
CGMs and Meal Planning
For someone with diabetes, CGM information can be incorporated into individualized meal planning. Rather than simply providing a list of foods to avoid, a dietitian can look at the entire meal.
For example, if a person experiences significant post-meal hyperglycemia after a meal containing a large portion of refined carbohydrate, the solution may not be “never eat carbohydrates again.”
Instead, we might explore:
- Reducing the portion
- Increasing fiber
- Adding protein
- Including unsaturated fats
- Pairing carbohydrates with other foods
- Choosing less refined carbohydrate sources
- Adjusting meal timing
- Adding appropriate physical activity
- Reviewing medication timing with the medical team
The right strategy depends on the individual. This is one of the strengths of CGM technology: it can help make nutrition recommendations more personalized.
Exercise and CGMs
Physical activity is another area where CGMs can provide useful information.
Exercise affects glucose in different ways depending on the type, intensity, duration, timing, and individual physiology. Aerobic exercise may lower glucose, while high-intensity or resistance exercise can sometimes temporarily increase glucose due to hormonal responses.
For someone with diabetes, especially someone using insulin or medications that can cause hypoglycemia, understanding these patterns can be extremely important.
For someone without diabetes, CGM data can also demonstrate how movement affects glucose.
A person might notice that a short walk after a meal is associated with a different glucose pattern than sitting immediately after eating.
The important point is not to become obsessed with achieving a specific post-meal glucose curve. Instead, the information can reinforce something we already know from decades of research: regular physical activity is beneficial for metabolic and cardiovascular health. The CGM is simply another way to visualize one aspect of that process.
Sleep, Stress, and Glucose
Food isn’t the only thing affecting glucose.
Sleep and stress can influence glucose regulation as well.
Someone might eat the same breakfast on two different days and see different glucose patterns.
Why?
Perhaps they slept poorly.
Maybe they were stressed.
Maybe they exercised differently.
Maybe they ate dinner later the night before.
Maybe their menstrual cycle influenced their physiology.
Maybe they were becoming ill.
This is another reason I encourage people not to automatically blame food for every glucose fluctuation. CGM data can demonstrate that metabolism is influenced by much more than individual food choices. This can actually be empowering. It reminds us that health is not determined by one meal.
CGMs and Weight Loss
CGMs are sometimes promoted as weight-loss tools.
There is some logic behind the idea that increased awareness could influence behavior. However, a CGM should not be viewed as a magic weight-loss device.
Weight regulation is influenced by many factors, including energy intake, energy expenditure, appetite regulation, sleep, medications, genetics, environment, stress, and individual physiology.
A person does not need to avoid every glucose rise to lose weight. In fact, obsessively trying to minimize glucose fluctuations can sometimes encourage unnecessary restriction. A dietitian can help keep weight-management goals focused on sustainable habits rather than chasing perfect CGM graphs.
When CGM Data May Become Harmful
More information is not always better. For some people, constant glucose monitoring can increase anxiety around food.
Someone may begin checking their glucose repeatedly, feeling guilty after meals, avoiding foods they enjoy, or interpreting normal physiological changes as evidence that they are unhealthy.
This is particularly concerning for people who already have a difficult relationship with food or who are prone to restrictive eating. If wearing a CGM makes someone afraid to eat, afraid of carbohydrates, or constantly worried about their glucose, it may not be providing a health benefit.
Technology should support health, not become another source of distress.
This is an important reason to consider working with a registered dietitian when interpreting CGM information.
What Should People with Diabetes Do with CGM Data?
For someone with diabetes, CGM information should be incorporated into an overall diabetes management plan.
A dietitian can help identify patterns related to:
- Carbohydrate intake
- Meal timing
- Portion sizes
- Fiber
- Protein
- Physical activity
- Hypoglycemia prevention
- Medication timing
- Meal composition
Medication decisions, particularly insulin dosing, should be made according to the individual’s diabetes treatment plan and medical guidance.
CGM data should not encourage someone to independently change medication doses without appropriate instruction from their health care team.
The ADA also emphasizes the importance of individualized goals and shared decision-making when interpreting CGM data.
What Should People Without Diabetes Do with CGM Data?
For people without diabetes who choose to use a CGM, I recommend approaching it as an experiment rather than a report card.
Instead of asking:
“Did I get a perfect glucose score?”
Ask:
“What can I learn?”
For example, you could observe how your glucose responds to:
- A balanced breakfast
- A higher-fiber meal
- A meal containing mostly refined carbohydrates
- A meal followed by a walk
- A meal followed by prolonged sitting
- Adequate sleep
- Poor sleep
You may discover patterns that help you make practical changes. But remember: one person’s glucose response does not establish universal nutrition rules. If your CGM shows that you respond differently to a particular food than someone else does, that does not mean your body is “broken.” Individual variation is normal.
CGMs Are Tools, Not Judges
Perhaps the most important message I can give as a dietitian is that a CGM should be treated as a tool.
It should not be treated as a judge.
A glucose reading is not a grade for your meal.
A glucose spike does not mean you failed.
A low reading does not automatically mean you ate incorrectly.
And a relatively flat glucose response does not automatically mean you made the “perfect” nutritional choice.
Health is determined by patterns over time, not by one meal or one glucose reading.
For people with diabetes, CGMs can provide clinically meaningful information that improves safety, treatment decisions, and glucose management. The evidence and recommendations supporting CGM use are strongest in people with diabetes who have specific treatment and monitoring needs.
For people without diabetes, CGMs may offer an interesting way to learn about individual glucose patterns, but the evidence is still developing, and CGMs should not be used to diagnose diabetes or prediabetes.
The Bottom Line
CGMs are an exciting piece of diabetes technology.
For people with diabetes, they can provide valuable real-time information that supports safer and more effective diabetes management. They can help identify glucose patterns, detect hypoglycemia, evaluate time in range, and provide insight into how food, activity, and medication interact.
For people without diabetes, CGMs may provide useful information about individual responses to food and lifestyle behaviors, but they should be approached with caution.
The goal should not be to eliminate carbohydrates. It should not be to prevent every glucose rise. It should not be to achieve a perfectly flat line. And it should not be to let an app determine which foods you are “allowed” to eat.
Instead, use CGM data as one piece of information within a much larger picture of health.
Eat a varied diet.
Include fiber-rich carbohydrates.
Prioritize adequate protein.
Include fruits and vegetables.
Choose healthy sources of fat.
Move your body regularly.
Prioritize sleep.
Manage stress when possible.
Enjoy your food.
And if you use a CGM, learn from the data without allowing the data to dictate your relationship with food.
The best use of a CGM is not to create fear around glucose, it is to create understanding.
As dietitians, our role is not simply to look at a glucose graph and tell someone what foods to eliminate. Our role is to interpret the information within the context of the whole person and help turn data into realistic, sustainable nutrition strategies.
Because ultimately, the healthiest diet is not the one that produces the prettiest CGM graph. It is the one that supports your health, meets your nutritional needs, fits your life, and allows you to have a healthy relationship with food.
If you’re using, or interested in using, a CGM to help with your health goals, talk to your primary care provider and dietitian about using it to the full extent!
Resources
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https://pubmed.ncbi.nlm.nih.gov/39755436
https://pubmed.ncbi.nlm.nih.gov/37503002
