| Pre-run glucose target | 126β180 mg/dL |
| CGM lag time during exercise | 5β15 minutes |
| Carb intake for runs >60 min | 30β60g per hour |
| Hypo treatment dose | 15β20g fast-acting carbs |
| Delayed hypoglycemia window | 6β12 hours post-run |
Key Takeaways
- CGMs provide real-time glucose data during runs, reducing hypoglycemia risk
- Placement and adhesion are critical for active athletes
- Target glucose range before a run is typically 126β180 mg/dL
- Trend arrows matter as much as the number itself
- Proper fueling strategies differ for Type 1 vs Type 2 athletes
What Is a CGM and Why Does It Matter for Runners?
A Continuous Glucose Monitor (CGM) is a wearable sensor that measures interstitial glucose every 1β5 minutes. For runners with diabetes, this real-time data replaces guesswork about fueling, insulin timing, and crash prevention. Unlike fingerstick tests, a CGM shows direction and rate of change β critical when glucose can drop rapidly mid-run.
Best CGM Placement for Runners
Recommended Sites
- Upper arm (tricep area): Most popular for runners; low movement zone
- Abdomen: Works well but prone to compression lows if wearing a waistband
- Upper buttock: Excellent accuracy, good adhesion
Keeping Your CGM Secure
Sweat, friction, and arm swing can dislodge sensors. Use medical-grade overtape or adhesive patches designed for athletes. MDS Diabetes stocks a range of CGM adhesive patches and overtape compatible with Dexcom, Libre, and Medtronic sensors to keep your device locked in through long runs.
Pre-Run Glucose Targets
| Scenario | Target Range |
|---|---|
| Easy/moderate run (<60 min) | 126β180 mg/dL |
| Long run (>60 min) | 144β180 mg/dL |
| High-intensity intervals | 140β200 mg/dL |
| Post-meal run | Wait for stable/falling trend below 250 mg/dL |
Reading Trend Arrows While Running
The glucose number alone is not enough. A reading of 140 mg/dL with a double-down arrow demands immediate action; the same number with a flat arrow is comfortable. Learn to act on arrows, not just values.
- ββ or β: Rising fast β reduce carbs, check for missed bolus
- β: Stable β maintain current fueling plan
- β or ββ: Treat immediately with 15β20g fast carbs
Fueling Strategies by Run Type
Runs Under 45 Minutes
For most Type 2 athletes, no extra carbs are needed. Type 1 athletes should reduce basal or pre-run bolus by 20β50% based on individual response.
Runs Over 60 Minutes
Consume 30β60g carbohydrates per hour. Check CGM every 20β30 minutes and adjust. Keep fast-acting glucose (gels, tablets) accessible. MDS Diabetes carries glucose tablets and running belts designed for easy mid-run access.
CGM Accuracy During Exercise
Interstitial glucose lags blood glucose by 5β15 minutes during rapid changes. During intense exercise, this lag is more pronounced. CGMs may also read low during heavy perspiration or compression. Always confirm with a fingerstick if symptoms don't match your CGM reading before treating aggressively.
Post-Run Management
Exercise-induced hypoglycemia can occur 6β12 hours after a long run. Continue CGM monitoring and consume a balanced recovery meal within 30β60 minutes. Reduce overnight basal if using an insulin pump after intense sessions.