Nutrition, Diet & Fasting - Food foundations
Continuous glucose monitors if you are not diabetic
By Ryan Lowe. Last reviewed 3 August 2026. How we write this.
A medical device now sold to people without diabetes. The data is real; what most people conclude from it usually is not.
A continuous glucose monitor is a small sensor worn on the arm that samples glucose in the fluid between cells every few minutes and streams the readings to a phone. For people with type 1 diabetes it is a genuinely transformative technology, replacing finger-prick testing and materially improving control and safety. That clinical value is not in question anywhere in this lesson.
What is newer is the consumer market: CGMs sold with apps and subscriptions to people with normal glucose regulation, promising personalised nutrition insight. That is a different proposition with a much thinner evidence base.
What the data actually shows you
Glucose rises after eating. In someone without diabetes, it then comes back down, because that is what functioning glucose regulation does. The size and shape of the rise varies with the food, but also with sleep, stress, illness, exercise, the time of day, what was eaten at the previous meal, and where the sensor happens to be sitting.
Two technical points get missed and both matter. Interstitial glucose lags blood glucose by roughly ten to fifteen minutes, so the curve on the phone is behind reality. And consumer sensors carry an error margin of several percent, with meaningful variation between two sensors worn simultaneously on the same person - which is enough to change the apparent ranking of two similar foods.
The interpretation problem
The core issue is that a "spike" in someone without diabetes is a normal physiological response, not a malfunction. There is no established threshold for what constitutes a harmful post-meal rise in a person with normal glucose tolerance, and no trial showing that a healthy person who flattens their curves ends up healthier. The outcome data that motivates glucose control comes from people with diabetes or prediabetes, where the whole point is that regulation is impaired.
The most reproducible finding from the research that got this field going is that different people respond differently to the same food - which is genuinely interesting science. Turning that into "therefore buy a sensor and eliminate the foods that spike you" is a large step the evidence has not taken. In practice the foods that produce the biggest rises are largely predictable without a sensor.
Where it can be useful
Two honest cases. For someone with prediabetes or a strong family history, seeing responses directly can be a more persuasive prompt to change than a number on an annual blood test - a behavioural benefit rather than a diagnostic one. And for an athlete managing fuelling around endurance events, the data has practical uses. Neither of those is the marketing pitch.
There is also a documented downside worth naming. Anxiety about readings, and food restriction driven by curve-chasing, are reported by users and are a plausible harm in anyone predisposed to disordered eating. A device that turns every meal into a score is not neutral for everyone.
Where the evidence stops
There are no long-term outcome trials of CGM use in healthy people. There is no validated definition of a "good" glucose curve in someone without diabetes. And a genuine diagnosis of impaired glucose regulation is made with HbA1c or a formal glucose tolerance test through a doctor - not from a consumer sensor's app.
Educational content only and not medical advice. A continuous glucose monitor is not a diagnostic tool for someone without diabetes; if you are concerned about your blood sugar, an HbA1c test through a GP is the appropriate route.
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Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.
