Continuous Glucose Monitoring (CGM)

What continuous glucose monitoring reveals

Continuous glucose monitors (CGMs) track glucose levels in real-time through a small sensor placed under the skin. Unlike fingerstick measurements that capture a single moment, CGMs record data every few minutes, revealing patterns you would otherwise miss. For people with diabetes, this technology has transformed management. For metabolically healthy individuals, CGMs offer a window into how food, sleep, stress, and exercise affect blood sugar.

Glucose variability matters as much as average levels. Sharp spikes followed by crashes signal metabolic inflexibility and inflammation. Research links high glucose variability to cardiovascular disease, cognitive decline, and accelerated aging ^[1][2]. A CGM shows you exactly which foods and behaviors produce these problematic patterns.

How CGMs work

The sensor measures glucose in interstitial fluid, the liquid surrounding cells. Readings lag behind blood glucose by 5-15 minutes, which matters during rapid changes like exercise. Most sensors last 10-14 days and transmit data to smartphones or dedicated receivers.

Key metrics include time in range (70-140 mg/dL for non-diabetics), average glucose, and coefficient of variation (aim for under 15%) ^[5]. Postprandial peaks above 140 mg/dL suggest poor metabolic response to that meal. Frequent dips below 70 mg/dL indicate reactive hypoglycemia.

Personalizing nutrition with CGM data

CGMs expose the myth that everyone responds the same way to the same foods. Two people eating identical meals can show vastly different glucose curves. Factors influencing response include microbiome composition, sleep quality, stress levels, and recent exercise ^[3].

Use CGM data to test food combinations. Adding protein, fat, or fiber to carbohydrates typically flattens the glucose curve. Walking 10-15 minutes after eating reduces peak glucose by 20-30% ^[4]. Some individuals discover they tolerate white rice better than brown, or that fruit spikes them more than expected.

Non-diabetic use: learning tool or lifestyle?

For healthy individuals, CGMs function best as educational tools over 2-4 weeks, not permanent fixtures. The goal is learning your metabolic responses, identifying problematic patterns, and establishing habits that maintain stable glucose. Long-term continuous use rarely provides additional benefits once patterns are understood.

Interpreting your data

Fasting glucose should stay between 70-90 mg/dL. Post-meal peaks ideally remain under 120 mg/dL, with return to baseline within 2-3 hours. Overnight trends reveal how dinner choices and timing affect sleep. Morning glucose elevations after poor sleep demonstrate the cortisol-glucose connection.