A continuous glucose monitor (CGM) is a small sensor worn on your arm or abdomen that reads glucose every 1–5 minutes for 10–14 days.
How it works
A tiny filament under the skin measures glucose in interstitial fluid (the fluid between cells). A transmitter sends readings to your phone or a separate receiver.
The major players
### Dexcom G7 - 10-day wear - 1-minute readings - Real-time alerts for highs and lows - Most accurate of the consumer CGMs - Requires prescription (US)
### Freestyle Libre 3 - 14-day wear - 1-minute readings - Slim, cheaper than Dexcom - Requires prescription (US)
### Stelo (Dexcom) - 15-day wear - Over-the-counter (US) since 2024 - Targeted at non-diabetics and prediabetics - No real-time hypo alerts
### Lingo (Abbott) - 14-day wear - Over-the-counter - Wellness-focused, no medical alerts
Should non-diabetics wear one?
It's a useful learning tool. After 2–4 weeks, most people learn: - Which foods spike them most - The huge impact of post-meal walking - Stress and sleep effects - Their personal carb tolerance
After the learning phase, ongoing use is unnecessary for healthy people.
CGM + Carb Lens
A CGM shows you what happened. Carb Lens predicts what *will* happen — by estimating glycemic load from a photo before you eat. Used together they're a powerful feedback loop.