Longevity Medicine
What Is Continuous Glucose Monitoring (CGM)?
Last reviewed: May 2026 · Haute MD Editorial Team
Continuous glucose monitoring (CGM) uses a small sensor inserted just beneath the skin surface that measures interstitial glucose (glucose in the fluid surrounding cells) every 1-5 minutes — transmitting readings to a smartphone or receiver in real time. Originally developed for diabetes management, CGM is increasingly used by metabolically healthy adults to understand how their blood glucose responds to specific foods, meals, exercise, stress, and sleep — information that fasting glucose and HbA1c measurements completely miss. CGM reveals the significant individual variation in glucose response to identical foods and identifies hidden glucose patterns that contribute to metabolic dysfunction.
What CGM reveals that standard labs cannot
Fasting glucose and HbA1c measure average glucose at a single point (fasting) and over 3 months respectively — they miss the glucose dynamics that occur after meals and overnight. CGM reveals — postprandial glucose spikes (how high blood sugar rises after specific meals); glucose variability (how much blood sugar fluctuates throughout the day — high variability independently predicts metabolic disease risk); time in range (what percentage of time blood sugar is in the optimal range of 70-140 mg/dL); nocturnal hypoglycemia (low blood sugar during sleep — affects sleep quality and morning cortisol); and individual food response (the same meal can produce wildly different glucose responses in different people — CGM personalizes dietary guidance).
Who benefits from CGM
People with diabetes or prediabetes — CGM is established clinical care for type 1 diabetes and increasingly for type 2 diabetes and prediabetes. Metabolically healthy adults seeking optimization — a 2-week CGM wear reveals which foods cause glucose spikes in that individual, identifying personalized dietary adjustments that standard nutritional guidelines miss. Athletes — CGM optimizes fuel timing for training and competition. People with insulin resistance — CGM quantifies the problem and tracks response to dietary intervention. Longevity medicine patients — glucose variability, time in range, and post-meal patterns provide more granular metabolic health information than annual fasting labs.
How to use CGM for metabolic optimization
Wear the sensor for 2 weeks (one Libre 3 sensor lasts 14 days). Log meals, exercise, stress, and sleep during the wear period. Analyze which meals produce the largest glucose spikes — typically refined carbohydrates, large fruit portions, sweetened beverages, white rice, and certain individuals' unexpected responses (some people spike significantly to oatmeal or brown rice). Identify exercise effects — aerobic exercise typically lowers glucose; resistance exercise may transiently raise it. Observe sleep disruption effects — poor sleep consistently elevates the next day's fasting glucose. Use findings to personalize diet and lifestyle, then recheck with a second CGM wear 3-6 months after changes.
Frequently Asked Questions
Do I need a prescription for a CGM?
Traditionally yes — CGMs required a prescription. As of 2024, the FDA has cleared over-the-counter CGMs for adults without diabetes: Dexcom Stelo and Abbott Lingo are available without prescription at pharmacies and online. Prescription CGMs (Libre 3, Dexcom G7) are covered by insurance for diabetes patients. OTC CGMs cost approximately $49-$89 per 14-day sensor. Subscription programs through companies like Levels Health and Nutrisense provide sensors plus an app with dietary guidance and physician review.
What is a normal glucose level on CGM?
Optimal CGM metrics for metabolically healthy adults — fasting glucose 70-90 mg/dL; post-meal peak below 140 mg/dL (ideally below 120 mg/dL); glucose variability (coefficient of variation) below 36%; time in range (70-140 mg/dL) above 90%. Spikes above 140 mg/dL after meals are common even in 'normal' individuals — but high-frequency spikes above 140 mg/dL are associated with accelerated metabolic dysfunction over time.
Is CGM accurate without diabetes?
CGM accuracy in non-diabetic individuals is slightly lower than in diabetic patients (CGMs are FDA-cleared and optimized for the glucose ranges relevant to diabetes). For non-diabetic metabolic optimization, CGM is sufficiently accurate to identify meaningful patterns in individual glucose response to food and lifestyle — the relative response to different foods and activities is reliable even if absolute accuracy at any single reading is imperfect.
How much does CGM cost for non-diabetic use?
OTC CGMs (Dexcom Stelo, Abbott Lingo) — approximately $49-$89 per 14-day sensor, available without prescription. Subscription platforms (Levels, Nutrisense) — $200-$400/month including sensors, app, and dietitian/physician review. For a one-time metabolic assessment, two sensors (4 weeks total) at $100-$180 OTC cost provides substantial information about personal glucose patterns.
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