CGMs Are Not Just for Diabetics Anymore

What a CGM Actually Does

A continuous glucose monitor is a small sensor — about the size of a two-pound coin — that you insert just under the skin, typically on the back of your upper arm. A thin filament sits in the interstitial fluid and measures glucose concentration every 1–5 minutes, transmitting data to your phone.

They were designed for people with type 1 diabetes who need to track blood sugar around the clock without finger-prick tests. Then type 2 diabetics started using them. Then people at risk of diabetes. Now companies like Levels Health, Nutrisense, and Supersapiens are selling CGM subscriptions to people with no metabolic disease at all — just curiosity about their own glucose patterns.

The data they produce is genuinely interesting. The questions about what to do with it are more complicated.

What You’ll See (And What Surprises People)

When metabolically healthy people wear CGMs for the first time, a few things tend to surprise them:

The magnitude of the oat spike. Oatmeal with berries — the canonical “healthy breakfast” — produces a significant glucose spike in a large proportion of people. The spike itself isn’t necessarily harmful, but the visual confirmation tends to be jarring when you’ve been eating oats as a health food for years.

Individual variation is massive. The same meal produces wildly different glucose responses in different people. A 2015 Weizmann Institute study (Zeevi et al., Cell) showed that identical foods produced glucose spikes that varied up to tenfold between individuals, based on gut microbiome composition, genetics, and other factors. This is why population-level glycaemic index tables have limited predictive value for any individual.

Exercise timing matters. A brisk 10-minute walk after eating can blunt a glucose spike by 20–30%. Strength training creates a different pattern — often a temporary rise during the session as glycogen mobilises, followed by improved glucose uptake for hours afterward.

Sleep and stress show up in the data. Poor sleep and high cortisol both impair insulin sensitivity in measurable ways. People often see their fasting glucose 5–10 mg/dL higher after bad nights.

What the Data Doesn’t Tell You

Here’s where I want to push back on some of the CGM marketing narrative.

Glucose spikes alone don’t tell you much about long-term metabolic health. Postprandial glucose excursions — spikes after meals — are one factor in metabolic health, but not the only one. A spike to 160 mg/dL that returns to baseline within 90 minutes is metabolically very different from chronic fasting hyperglycaemia. The CGM captures the spike but not the full context.

The optimal glucose range for non-diabetics is not established. CGM apps often show “optimal zones” and colour code your data green or red. These ranges are largely derived from diabetic and pre-diabetic populations, not healthy people. We don’t actually know whether optimising glucose variability in a metabolically healthy person improves long-term outcomes.

Food fear is a real risk. A meaningful subset of people who wear CGMs — particularly those with any history of disordered eating — develop anxiety about glucose spikes and start restricting foods based on real-time data. If you have this tendency, the biofeedback loop of a CGM may not serve you well.

Is It Worth Doing?

For most metabolically healthy people, one 30-day CGM trial is genuinely educational. You’ll almost certainly learn something about how your body responds to food that no dietary guideline could have told you — because dietary guidelines describe populations, not you.

The consistent behavioural change I see from CGM users: walking after meals becomes habitual. It’s low-effort, the glucose data makes the benefit immediate and visible, and the habit sticks. That’s a real outcome.

Beyond the initial trial, the value proposition weakens for healthy people. Monthly CGM subscriptions run $100–$200/month. If you’ve already done the trial and identified your personal high-spike foods, additional monitoring is unlikely to produce proportionally useful new information.

Use it as an educational tool, not a permanent monitoring device. Learn your patterns, adjust accordingly, then put the sensor down.

Who Should Consider a CGM Trial

• Anyone with family history of type 2 diabetes
• Anyone experiencing unexplained fatigue, brain fog, or energy crashes
• Anyone genuinely curious about how their specific diet affects their physiology
• Athletes wanting to optimise carbohydrate timing around training

Who Should Be Cautious

• Anyone with a history of eating disorders or food anxiety
• Anyone who tends toward health anxiety and compulsive monitoring
• Anyone expecting a CGM to replace a relationship with a registered dietitian