Continuous Glucose Monitors (CGMs) in 2025: The Complete Guide

Continuous Glucose Monitors (CGMs) have gone from a medical necessity for people with diabetes to one of the hottest tools in health optimization. Peter Attia, Levels Health, and a growing wave of biohackers are pushing CGMs into the mainstream for longevity, performance, and nutrition.

In 2025, the game changed: Dexcom launched Stelo, the first FDA-cleared over-the-counter CGM, now available directly on Amazon. No prescription, no doctor’s note — just real-time glucose insights for anyone who wants them.

This guide covers the latest science, the best CGM options, practical tips, and answers to the most common questions.

Why Glucose Control Matters for Everyone

Glucose isn’t just about diabetes. It’s the body’s primary fuel source, and when blood sugar regulation goes off track, the ripple effects are enormous.

• Metabolic health: Chronically high or erratic glucose levels contribute to insulin resistance — the root of metabolic syndrome. This cluster of conditions (high blood pressure, high blood sugar, belly fat, and abnormal cholesterol) dramatically raises the risk for heart disease and stroke.

• Pre-diabetes: Over 96 million American adults are estimated to have pre-diabetes, often without knowing it. At this stage, lifestyle changes can reverse the course before it progresses to type 2 diabetes.

• Brain health: Researchers now refer to Alzheimer’s as “type 3 diabetes” because impaired glucose metabolism in the brain is linked to cognitive decline. Stable blood sugar may help protect long-term memory and mental performance.

In short: managing glucose isn’t just for people with diabetes — it’s a cornerstone of longevity, performance, and everyday energy.

Why CGMs Matter

• Glucose Stability = Longevity: High glucose variability is linked to faster aging and disease. Keeping blood sugar steady protects your mitochondria, brain, and cardiovascular system.

• Metabolic Flexibility: A CGM helps you see how carbs, fat, fasting, and exercise affect your metabolism in real time.

• Performance & Recovery: Athletes use CGMs to fuel smarter — from Tour de France cyclists coached by Iñigo San-Millán to UFC fighters tracking training recovery. Even if they don’t have diabetes, athletes care because stable glucose means better endurance, faster recovery, and optimized fueling strategies in competition.

• Personalized Nutrition: Instead of guessing, CGMs show how your body reacts to foods. Two people can eat the same meal and have completely different glucose responses.

From Finger Pricks to Wearables: The Evolution of Glucose Monitoring

Not long ago, the only way to know your blood sugar was with a handheld meter and a lancet. That meant pricking your finger several times a day, squeezing out a drop of blood, and waiting for a single reading. It gave you one data point — but no context about how your levels changed after a workout, a meal, or while you were asleep.

Today’s continuous glucose monitors (CGMs) changed that completely. Instead of a painful prick, a CGM uses a tiny sensor placed just under the skin that can measure glucose around the clock. Modern devices like the Dexcom Stelo or the Abbott FreeStyle Libre stream that data to your phone, letting you see real-time graphs and trends.

For athletes, this is a game-changer. They don’t just see a fasting glucose number; they can watch how an interval workout spikes glucose, how a recovery meal stabilizes it, or how a late-night snack disrupts overnight blood sugar. For anyone interested in performance or longevity, it’s like moving from a Polaroid snapshot to a full HD video of your metabolism in action.

The Best CGM Options in 2025

• Dexcom Stelo (NEW) – First OTC CGM in the US, sold on Amazon. No prescription required. Ideal for non-diabetics who want glucose tracking without jumping through medical hoops.

• Dexcom G7 – The gold standard for accuracy, FDA-cleared for diabetes, prescription only in the US.

• Abbott FreeStyle Libre 3 – Affordable, widely available, usually requires a prescription in the US but easier to access abroad.

• Supersapiens – Built on Abbott hardware, tailored for athletes and endurance training.

• Levels Health – Subscription-based app layered on Abbott tech, focused on lifestyle coaching. If you sign up with Levels, their network of doctors will review and approve your prescription entirely online. You don’t have to book an in-person appointment — it’s seamless and handled virtually.

• Veri – Strong European presence, excellent UI for lifestyle and longevity tracking.

How to Use a CGM for Health Optimization

• Track Your Baseline: Wear your CGM for 2 weeks without changing much. See how your body reacts to food, sleep, and stress.

• Test Meals: Try high-carb, high-fat, and mixed meals. Notice which spike your glucose.

• Experiment with Timing: Compare eating carbs earlier vs later in the day. Many people see better glucose control earlier.

• Use with Exercise: See how walking after meals, Zone 2 cardio, or HIIT affect your glucose recovery.

• Cross-check with Other Data: Pair your CGM with biomarkers like HRV, sleep data, or blood labs for deeper insights.

Advanced Strategies

• Berberine & Metformin: Both lower blood sugar, but they work differently. Using a CGM helps you see which one actually benefits your metabolism.

• Meal Stacking: Eating protein and fiber before carbs can blunt spikes.

• Cold Exposure & Fasting: Both can improve insulin sensitivity — CGMs let you measure the effect.

• Sleep & Stress Tracking: Poor sleep and high stress can spike glucose, even without food.

Continuous Glucose Monitor (CGM) FAQ

Do I need a prescription for a CGM?
Not anymore. In 2025, Dexcom Stelo became the first CGM available OTC in the US, sold directly on Amazon. You do still need a prescription for devices like the Dexcom G7 or Abbott FreeStyle Libre if you’re getting them through traditional healthcare channels. If you use services like Levels, the prescription is handled online with their network of doctors — no need to visit your own physician.

How long does a CGM last?
Most sensors last 10 to 14 days before they need to be replaced. Some systems automatically send data to your phone, while others require scanning.

Does a CGM hurt to insert?
Insertion is quick and almost painless. Most people describe it as less noticeable than a finger-prick test.

Can I shower or swim with a CGM?
Yes — modern sensors are water-resistant and designed to stay on through normal daily life, including exercise, showers, and swimming.

Do CGMs measure in real time?
Yes. Devices like Dexcom and Abbott Libre stream continuous readings, typically updating every 1–5 minutes, so you can track glucose changes live.

Are CGMs only for people with diabetes?
Originally yes, but now many people without diabetes use them for nutrition optimization, athletic performance, and longevity tracking. The launch of Dexcom Stelo marks the official mainstreaming of CGMs for health enthusiasts.

How accurate are CGMs?
The top devices (Dexcom G7, Abbott Libre 3) are highly accurate and FDA-approved. For precise medical use, finger-stick checks may still be recommended occasionally, but for lifestyle and performance tracking, they’re more than reliable.

How do I know if lifestyle changes are working?
That’s the power of CGMs. You can run real-time experiments — swap out meals, add Zone 2 cardio, try berberine — and watch the impact instantly.

The Future of CGMs: Non-Invasive Monitoring

The tech doesn’t stop here. Companies like Apple and Samsung have been quietly working on non-invasive glucose monitoring for years. Instead of a tiny filament under the skin, the goal is to measure blood sugar using light, spectroscopy, or other external sensors.

If Apple integrates this into the Apple Watch — a rumor that surfaces every year — it could make metabolic tracking mainstream overnight. Imagine millions of people checking their glucose the way they check steps or heart rate today.

Until then, current CGMs like Dexcom and Abbott remain the most accurate and accessible options. But the future is clear: glucose monitoring is moving from the clinic to the wrist, and from managing disease to optimizing everyday health and performance.

The Bottom Line

CGMs are no longer just for managing diabetes — they’re for anyone who wants to optimize health, performance, and longevity. With Dexcom Stelo now available OTC on Amazon, the barrier to entry has disappeared.

Whether you’re curious about how your favorite breakfast affects your metabolism, want to compare berberine vs metformin, or want to fine-tune training recovery like an elite athlete, CGMs are the ultimate feedback loop.

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