What is a continuous glucose monitor (CGM)?

How CGMs work, the difference between Dexcom, Libre and Stelo, and whether non-diabetics benefit from wearing one.

Written by

Carb Lens Editorial

Nutrition writers & product team

Medically reviewed by

Dr. Alicia Nguyen, RD, CDCES

Registered Dietitian · Certified Diabetes Care & Education Specialist · 12+ years clinical experience

Published June 19, 2026 4 min readEditorial policy

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.

About the author

Carb Lens Editorial — Nutrition writers & product team. The Carb Lens editorial team writes practical, source-checked guides on carbs, blood sugar, and everyday nutrition. Every article is drafted by our writers and cross-referenced against USDA FoodData Central and peer-reviewed clinical guidelines.

How we source and review this article

Nutrition figures come from the USDA FoodData Central database. Blood-sugar and glycemic-load framing follows guidance from the American Diabetes Association and World Health Organization healthy-diet recommendations. Every article is medically reviewed by Dr. Alicia Nguyen, RD, CDCES before publishing and re-checked on a rolling basis. See our full editorial & medical review policy.

This article is for general information and is not a substitute for medical advice. If you're managing diabetes or another condition, always defer to your care team.