Medically reviewed by Dr. Pamela Frank, BSc(Hons), ND August 2026
Over the past few years, continuous glucose monitors (CGMs) have become one of the fastest-growing wellness trends. Once reserved almost exclusively for people living with diabetes, CGMs are now marketed to healthy adults who want to optimize their diet, improve energy, lose weight, enhance athletic performance, and even slow aging.
The promise is appealing. Wear a small sensor on your arm, watch your glucose respond to every meal, and discover the “perfect” diet for your body.
The reality is more complicated.
For people with diabetes, CGMs have transformed diabetes management and are supported by decades of research. For people without diabetes, the scientific evidence is far less convincing. While CGMs can occasionally provide useful insights, they also have important limitations that are rarely discussed in marketing materials.
As a naturopathic doctor, I am often asked whether healthy individuals should wear a CGM. The answer depends on what you hope to learn. Understanding both the strengths and weaknesses of these devices can help you decide whether they are worth the investment.
What is a Continuous Glucose Monitor?
A continuous glucose monitor is a small sensor with a needle that is inserted just beneath the skin that measures glucose levels in the interstitial fluid surrounding your cells every few minutes.
Unlike finger-prick glucose testing, CGMs provide:
- 24-hour glucose measurements
- Trends over time
- Alerts for unusually high or low glucose
- Information about how meals, exercise, sleep and stress affect glucose levels
Common CGMs include the:
- Abbott FreeStyle Libre
- Dexcom G7
- Medtronic Guardian
Although they measure glucose continuously, they do not measure blood glucose directly. Instead, they estimate glucose from interstitial fluid, which typically lags behind blood glucose by approximately 5–15 minutes.
Why Are Healthy People Wearing CGMs?
Wellness companies frequently promote CGMs as tools to:
- identify “good” and “bad” foods
- personalize nutrition
- improve metabolic health
- prevent diabetes
- reduce inflammation
- increase energy
- optimize athletic performance
- lose weight
Many apps assign “scores” to meals based on glucose responses, suggesting that flatter glucose curves are inherently healthier.
The problem is that these claims have advanced much faster than the science supporting them.
What Does Normal Glucose Look Like?
Healthy glucose regulation is remarkably stable.
In most healthy adults:
- fasting glucose ranges from approximately 3.9–5.5 mmol/L (70–99 mg/dL)
- after meals, glucose commonly rises to 6.7–7.8 mmol/L (120–140 mg/dL)
- glucose typically returns toward baseline within two to three hours
Importantly, glucose responses vary considerably between healthy individuals.
Even within the same person:
- identical meals on different days can produce different glucose curves
- sleep quality changes responses
- stress changes responses
- recent exercise alters glucose handling
- menstrual cycle hormones influence glucose regulation
Some amount of variation is normal physiology.
Healthy People Frequently Have Glucose Spikes
One of the biggest surprises from recent research is how often completely healthy people experience glucose levels that would appear concerning if viewed without context.
Several studies using CGMs have shown that healthy individuals regularly experience:
- transient glucose levels above 7.8 mmol/L (140 mg/dL)
- occasional readings above 8.9 mmol/L (160 mg/dL)
- brief spikes approaching 11.1 mmol/L (200 mg/dL)
These elevations often last only minutes and occur without any evidence of diabetes.
A large international study published in PLOS Biology found enormous variability between healthy individuals eating identical meals. Some participants experienced almost no rise in glucose, while others had much larger responses despite having normal glucose tolerance.
This means that a single glucose spike does not necessarily indicate poor metabolic health.
Glucose is Only Part of the Story
This is perhaps the single biggest limitation of CGMs for people without diabetes.
Continuous glucose monitors measure glucose. They do not measure insulin. For many people seeking to improve metabolic health, insulin is actually the more important hormone. After eating carbohydrates, the pancreas releases insulin to move glucose into muscle, liver and fat cells.
Two people may show identical glucose curves while producing vastly different amounts of insulin.
For example:
Person A eats oatmeal. Their glucose rises modestly from 4.8 to 6.2 mmol/L. Their pancreas secretes a relatively small amount of insulin. Everything is functioning efficiently.
Person B eats the identical meal. Their glucose also rises from 4.8 to 6.2 mmol/L. However, their pancreas produces three or four times as much insulin to keep glucose in that same range.
The CGMs for Person A and Person B show virtually identical glucose responses. But, metabolically, these two individuals are very different. Person B may already have significant insulin resistance despite “excellent” glucose values.
This is especially relevant for individuals with:
- polycystic ovary syndrome (PCOS)
- obesity
- metabolic syndrome
- fatty liver disease
- strong family history of diabetes
Many of these individuals develop hyperinsulinemia years before fasting glucose becomes abnormal.
A CGM cannot detect this.
In clinical practice, fasting insulin, fasting glucose, HOMA-IR, oral glucose tolerance testing with insulin measurements, triglyceride-to-HDL ratio, and other metabolic markers often provide much more meaningful information than glucose alone.
Flat Glucose Curves Are Not Always Better
Many wellness companies encourage users to eliminate any meal that produces a noticeable glucose rise. Physiologically, this doesn’t make sense. A healthy pancreas is designed to respond to carbohydrates. A temporary rise in glucose followed by appropriate insulin release is normal.
In fact, very flat glucose curves can sometimes occur because:
- carbohydrate intake is extremely low
- exercise has depleted glycogen
- insulin secretion is excessive
- glucose has already been removed rapidly from circulation
Simply minimizing every glucose rise should not be the goal. Normal glucose variability is part of healthy metabolism.
Do CGMs Help People Eat Better?
The evidence on whether people actually eat better during and after using a continuous glucose monitor is mixed.
Some small studies show that wearing a CGM encourages healthier food choices simply because people become more aware of what they are eating and which foods are truly having a negative impact for them.
Users often:
- reduce sugary beverages
- eat smaller portions
- exercise more consistently
- become more mindful about meal timing
However, it is difficult to determine whether these improvements come from the CGM itself or from increased attention to health habits. Researchers call this the Hawthorne effect: people change their behaviour because they know they are being observed.
Several studies suggest that improvements often diminish after the device is removed.
Can CGMs Predict Diabetes?
Not very well. Type 2 diabetes develops gradually over many years. The earliest abnormality is usually insulin resistance, which, as I previously pointed out, a continuous glucose monitor doesn’t pick up.
The pancreas compensates by producing larger amounts of insulin. But the blood glucose may remain completely normal for years. Only after insulin production can no longer keep up does glucose begin to rise.
Because continuous glucose monitors only measure glucose, they miss this early phase entirely.
Someone can have:
- normal fasting glucose
- normal CGM readings
- normal HbA1c
while simultaneously having chronically elevated insulin levels. This is one reason why relying solely on glucose can provide false reassurance.
Exercise Can Produce Confusing CGM Readings
Exercise has complex effects on glucose.
- Moderate aerobic exercise usually lowers glucose.
- High-intensity exercise may temporarily increase glucose because adrenaline stimulates glucose release from the liver.
- Resistance training can produce variable responses depending on intensity and duration.
Without understanding exercise physiology, people sometimes misinterpret these temporary increases as harmful. In reality, they are often normal adaptive responses.
Stress and Poor Sleep Affect Glucose
One poor night’s sleep can significantly increase insulin resistance the following day. Psychological stress activates cortisol and adrenaline. Both hormones increase glucose availability.
A person may see elevated glucose after:
- an argument
- public speaking
- poor sleep
- illness
- intense exercise
These responses reflect normal stress physiology rather than poor dietary choices.
Are CGMs Accurate?
Modern continuous glucose monitors are impressively accurate, but they are not perfect.
Accuracy decreases:
- during rapid glucose changes
- shortly after meals
- during vigorous exercise
- when sensors are newly inserted
- if pressure is applied to the sensor during sleep
They also measure interstitial fluid rather than blood, creating a natural delay. For people with diabetes, these small differences rarely affect clinical decisions, but for healthy individuals analyzing every small fluctuation, they may become misleading.
Could CGMs Increase Food Anxiety?
Some researchers worry that excessive glucose monitoring may encourage unhealthy relationships with food. People may begin avoiding nutritious foods like fruit and beans because they produce modest glucose rises.
These foods often produce temporary glucose increases while providing fibre, vitamins, minerals and phytochemicals associated with long-term health.
Obsessing over every glucose peak can shift attention away from overall dietary quality.
Some experts have suggested that unnecessary glucose monitoring could contribute to orthorexia, an unhealthy fixation on eating “perfectly.”
When Might CGMs Be Helpful?
There are situations where CGMs may provide useful information outside of diabetes.
Potential examples include:
- identifying reactive hypoglycemia
- monitoring gestational diabetes (under medical supervision)
- investigating unexplained glucose variability
- helping motivate diet and lifestyle changes
- assessing responses to major dietary changes
Athletes experimenting with fueling strategies may also find short-term CGM use informative.
For most healthy adults, however, long-term continuous monitoring has not yet been shown to improve health outcomes.
Practical Advice About Continuous Glucose Monitors
If you decide to wear a CGM, keep the following principles in mind:
- Look for overall patterns rather than individual spikes.
- Consider sleep, stress, illness and exercise alongside meals.
- Focus on dietary quality rather than eliminating every glucose rise.
- Remember that glucose responses vary naturally from day to day.
- Avoid interpreting glucose values in isolation, ignoring insulin physiology.
Perhaps most importantly, remember that a “perfect” glucose graph does not necessarily mean optimal metabolic health.
A person may maintain completely normal glucose levels by producing very large amounts of insulin. Over time, chronic hyperinsulinemia is thought to contribute to weight gain, polycystic ovary syndrome, fatty liver disease, hypertension, cardiovascular disease, and eventually type 2 diabetes. Since CGMs provide no information about insulin secretion, they cannot identify this important early stage of metabolic dysfunction.
The Bottom Line on Continuous Glucose Monitors
Continuous glucose monitors are remarkable medical devices that have dramatically improved care for people with diabetes. Their growing popularity among healthy adults reflects increasing interest in personalized nutrition and metabolic health.
Current research suggests that continuous glucose monitors can increase awareness of lifestyle habits and may encourage healthier choices in some people. At the same time, there is little evidence that long-term CGM use improves health outcomes in individuals without diabetes.
The biggest limitation is that glucose represents only one piece of metabolic health. Many people develop insulin resistance years before blood glucose becomes abnormal. A continuous glucose monitor cannot distinguish between someone who maintains normal glucose with modest insulin production and someone whose pancreas is working overtime to keep glucose in the same range.
For this reason, glucose data should always be interpreted in context. Clinical history, body composition, family history, fasting insulin, lipid markers, and other metabolic measurements often provide a much more complete picture than glucose readings alone.
Rather than striving for a perfectly flat glucose line on a continuous glucose monitor, focus on the habits that consistently improve metabolic health: regular physical activity, restorative sleep, stress management, adequate protein, high-fibre whole foods, and maintaining a healthy body composition. These strategies improve both glucose regulation and insulin sensitivity, whether or not you’re wearing a sensor.
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