Continuous Glucose Monitoring: How to Read the Data Without Losing Your Mind

By Dr. Steven Long, DO, MHA, CPT
 Beyond Health | Precision Medicine for High-Performance Living

Continuous glucose monitors (CGMs) have moved from diabetes management into wellness, fitness, and longevity circles. They’re now worn by athletes, executives, and anyone curious about their metabolism.

When used correctly, CGMs offer remarkable insight. When misused, they can create unnecessary anxiety and confusion.

At Beyond Health, we teach patients how to interpret CGM data in context — not through fear, but through physiology.

1. The Basics: What CGM Actually Measures

A CGM tracks interstitial glucose, not blood glucose. Readings usually lag blood levels by about 5–10 minutes, which matters during exercise or rapid glucose changes.

Key terms:

• Time in Range (TIR): % of readings between 70–140 mg/dL (for non-diabetic optimization).
• Glucose Variability: How much your glucose fluctuates. A lower standard deviation (< 20 mg/dL) is ideal.
• Mean Glucose: Your average level, often correlating to an estimated A1C.
• GMI (Glucose Management Indicator): An estimate of A1C based on average CGM values.
• Postprandial Spike: Rise after eating, usually peaking 30–90 minutes post-meal.

For healthy adults, average glucose typically sits 80–100 mg/dL fasting, with transient post-meal rises below 140–160 mg/dL. But there’s nuance.

2. What “Normal” Looks Like

In real life, even metabolically healthy people see variability.

• Post-meal peaks: occasional readings up to 160–180 mg/dL after high-carb meals or intense exercise are not pathologic.
• Brief readings over 200 mg/dL can happen after large meals, desserts, or stress responses — they do not mean diabetes if glucose returns to baseline within two hours.
• Flatline graphs are unrealistic; glucose should move.

A good rule of thumb:

Glucose that rises and falls predictably is healthy. Glucose that stays high or fluctuates wildly without reason deserves more attention.

3. Common CGM Phenomena We See

A. Double Spikes

Two separate peaks following one meal.

• Often due to fat slowing digestion — the first spike is carb absorption, the second is delayed digestion.
• Sometimes caused by late snacking or dessert after the main meal.
  Interpretation: Normal physiology, not pathology.

B. Dawn Effect

Rise in glucose early morning (4–8 AM) from cortisol and growth hormone release.
Interpretation: A natural circadian rhythm, not “poor control.”

C. Exercise Spikes

High-intensity or anaerobic workouts raise glucose via epinephrine and hepatic glycogen release.
Interpretation: Adaptive and beneficial. Do not “correct” this.

D. Stress Spikes

Meetings, presentations, or poor sleep can transiently elevate glucose through cortisol.
Interpretation: A mirror of your stress response, not a reflection of diet.

E. Sensor Drift

CGMs sometimes show erroneous high or low readings — particularly during pressure on the sensor or at day 10+ of use.
Interpretation: Always cross-check with fingerstick if numbers don’t match how you feel.  Cross check when your CGM readings are stable instead of in a rise or fall pattern as this is a sure fire way to get inaccurate readings.

4. What We Actually Look For

In Beyond Health programs, we focus on patterns, not single numbers.

• Baseline stability: fasting glucose consistently < 100 mg/dL.
• Post-meal recovery: back to baseline within 2–3 hours.
• Time in range: ideally > 90% between 70–140 mg/dL.
• Daily variability: standard deviation < 20 mg/dL.
• Low frequency of spikes > 180 mg/dL, and quick return afterward.

When used this way, CGM becomes a behavioral feedback tool — showing how sleep, stress, and exercise alter your metabolism day to day.

5. Common Misinterpretations

• “Any spike = disease.” False. Glucose is supposed to move. What matters is how efficiently it returns to baseline.
• “I had a single 200 mg/dL reading — I must be insulin-resistant.” Not necessarily. Look at pattern and context.
• “My CGM showed 60 mg/dL after dinner — I’m hypoglycemic.” Possibly a sensor lag or compression error.
• “I need to eliminate all carbs to keep glucose flat.” Over-restriction can harm performance and recovery.

Data literacy matters as much as data collection.

6. Evidence and Context

• In healthy, non-diabetic adults, median glucose values range 76–117 mg/dL across 24 hours, with brief post-meal peaks to 160 mg/dL (Zhou et al., Diabetes Care, 2019).
• Continuous glucose monitoring studies in athletes show transient elevations during high-intensity work reflecting glycogen mobilization, not pathology (Hinkle et al., Med Sci Sports Exerc, 2021).
• Time-in-range metrics correlate strongly with cardiometabolic health and overall glycemic control, even in non-diabetics (Battelino et al., Diabetes Care, 2019).

In short: interpret the story, not the snapshot.

7. The Beyond Health Approach

We use CGM as part of a complete metabolic strategy — combined with lab markers (fasting insulin, A1C, lipids), wearable data, dietitian oversight, and physician interpretation.

We don’t aim for perfect flatlines.
We aim for metabolic resilience — a system that adapts to meals, stress, and training efficiently.

Your glucose curve should tell a story of adaptation, not anxiety.

Conclusion

Continuous glucose monitoring can be one of the most valuable self-tracking tools in modern medicine — if interpreted through physiology, not fear.

Occasional spikes are normal. Context matters.
 Patterns, not perfection, define metabolic health.

At Beyond Health, we help you read the story behind the numbers — and use that knowledge to build strength, energy, and longevity that actually lasts.

References

Battelino, T., et al. (2019). Clinical Targets for Continuous Glucose Monitoring Data Interpretation: Recommendations from the International Consensus on Time in Range. Diabetes Care, 42(8), 1593–1603.

Hinkle, J., et al. (2021). Continuous Glucose Monitoring in Athletes: Glucose Responses to Exercise and Recovery. Medicine & Science in Sports & Exercise, 53(12), 2629–2637.

Zhou, J., Li, H., Ran, X., et al. (2019). Reference values for continuous glucose monitoring in healthy Chinese subjects. Diabetes Care, 42(5), 849–855.