Managing Blood Sugar During Exercise: Part 2

 ‼️DISCLAIMER: although I am a healthcare professional, this post is not intended to be medical advice. This is simply me sharing some of what I know, but your body may not respond in this way so please make sure you are chatting with your diabetes educator and/or doctor first ‼️ or bring me onto your care team 😘

Exercise is essential for overall health, and for people with diabetes, it can have a significant impact on blood sugar regulation. However, because diabetes management involves many factors, exercise can sometimes feel like navigating a complex puzzle. The goal is to stay active while keeping blood sugar levels stable and avoiding unexpected highs or lows. This guide will help you understand how to manage blood sugar before, during, and after exercise, while incorporating key factors like fitness level, time of day, insulin timing, and more.

Always Be Prepared

Before diving into the specifics, remember these foundational principles for exercising safely with diabetes:

• Carry Fast-Acting Carbs: Always have a fast-acting carbohydrate option (or two) available. This could be anything from glucose tablets to a small snack, such as fruit or a granola bar. Hypoglycemia (low blood sugar) can sneak up during physical activity, so being prepared can make a world of difference.
  
  
• Hydration Matters: Staying hydrated is crucial, especially when blood sugar levels are running high or when you’re exercising outdoors or for an extended period. Dehydration can worsen blood sugar control, so drink plenty of water before, during, and after your workout.
  
  

Pre-Exercise Guidelines

2 Hours Before Movement

• Check Your Blood Sugar: This is the first step in assessing whether you're ready to exercise. If your blood sugar is in range (typically between 70–180 mg/dL, though this may vary), you're probably good to go. If it's high, consider taking about half of your usual correction dose. This helps to prevent excessive spikes during exercise.
  
  
• If In Range: If your blood sugar is in range, you may not need any extra insulin at this time. However, if you're planning for a long or intense workout, be mindful of how insulin may act during the session.
  
  

1 Hour Before Movement

• Snack for Stability: If you normally snack before exercise and your blood sugar is in range, a small snack can help stabilize your levels for optimal performance. Some ideas for a pre-workout snack include:
  
  
• A piece of fruit and a handful of nuts.
  
  
• A granola bar with some protein.
  
  
• A slice of toast with peanut butter.
  
  
• Fasted Exercise or Potential Spikes: If you're working out in a fasted state (e.g., early morning), or if you typically experience a spike during exercise, a small insulin dose around 20 minutes before starting can help prevent a sharp rise in blood sugar.
  
  
• If Blood Sugar is High: If your blood sugar is still high, and you've already corrected it, you may not need more insulin. If you haven’t corrected yet, consider a conservative correction dose.
  
  

Snack Suggestions (15–20g Carbs + 5–10g Protein):

• Fruit and a handful of nuts
  
  
• A granola bar with protein
  
  
• A slice of toast with peanut butter
  
  

Special Considerations: Time of Day & Activity Type

Your fitness level and training schedule have a significant impact on how your body responds to exercise. For example:

• The More Active You Are, the Greater Long-Term Benefits for Blood Sugar: Generally, the more active you are over time, the more your body adapts to managing blood sugar effectively. Regular physical activity can help improve insulin sensitivity, reducing the impact of spikes and dips over time.
  
  
• Time of Day Matters: It's not just about what type of exercise you're doing, but also when you're doing it. For instance, some individuals notice that their blood sugar behaves differently depending on the time of day. For example, I personally spike in the morning, while I tend to drop more easily in the afternoon. This has to do with my insulin sensitivity and the insulin on board from previous meals. When I strength train in the morning, my blood sugar tends to rise, but if I strength train in the afternoon, I remain stable.
  
  
• Morning vs. Afternoon Activity: The time of day can influence blood sugar stability. A morning walk might leave you steady, but an afternoon walk might cause your blood sugar to drop. Similarly, strength training may cause a blood sugar spike in the morning but keep you stable in the afternoon.
  
  
• Activity Type: Aerobic activities (such as walking, jogging, or swimming) are more likely to lower blood sugar, especially if insulin is active. In contrast, anaerobic exercises like strength training or high-intensity interval training (HIIT) tend to raise or stabilize blood sugar, even during intense efforts.
  
  
• Yoga’s Unique Impact: Even more gentle exercises like yoga can impact blood sugar, but the effect varies. For example, a stress-relieving yoga class could lower your blood sugar, while a more active or strength-based yoga session may have a neutral or even stabilizing effect.
  
  

The key takeaway is that blood sugar responses are complex and individual. Tracking trends in your own exercise routine and testing different strategies is essential for effective blood sugar management.

During Exercise

• Anaerobic Activities (HIIT, Strength Training): These activities may cause a rise or stabilization in blood sugar. They generally involve high-intensity efforts that deplete glycogen stores, prompting the liver to release glucose. This is more likely if you have insulin on board or are coming off a recent meal.
  
  
• Aerobic Activities (Walking, Swimming, Running): These activities tend to lower blood sugar, especially when combined with insulin on board. However, it’s important to monitor for potential lows, especially during extended cardio sessions.
  
  
• Hydration and Electrolytes: For longer sessions or heavy sweating, it’s important to hydrate and consider electrolytes in your water. These are essential to maintaining energy levels and helping you stay stable throughout your workout.
  
  
• Incorporate Carb Support for Long Sessions: For long or intense cardio sessions (such as running or cycling), it’s beneficial to consider carbohydrate support every 20–40 minutes. Start with 8–12g of carbs for a 1-hour session and adjust as necessary based on your blood sugar trends.
  
  

Post-Exercise Considerations

• Recovery Meal/ Snack: After exercise, it’s important to replenish glycogen stores and repair muscles. A balanced meal or snack with carbs and protein is essential for this process.
  
  
• Carbohydrates: Aim for 15–45g, depending on the intensity and duration of the exercise.
  
  
• Protein: Approximately 20–30g helps with muscle recovery.
  
  
• Protein Powders: Some protein powders, like whey, can cause a blood sugar rise due to the body’s response to the protein. Consider factoring this into your carb intake or choosing a protein option that doesn’t spike blood sugar as much.
  
  
• Post-Exercise Insulin Adjustments:
  
  
• Cardio/Aerobic Exercise: If you did aerobic activity, consider reducing your insulin dose by 30–40% in the hours following the workout. This compensates for the body’s increased insulin sensitivity.
  
  
• Strength-Based Exercise: For anaerobic exercise, your insulin dose may not need to be adjusted, but monitor closely for changes based on your individual patterns.
  
  

Pump-Specific Guidance

If you’re using an insulin pump, consider these tips to adjust for exercise:

• Activity Mode: Some pumps have an Activity Mode or Exercise Mode, which reduces insulin delivery to account for the increased insulin sensitivity that exercise creates. Consider enabling this mode about an hour before starting your workout.
  
  
• Post-Exercise Mode: If you're still feeling insulin-sensitive for several hours post-exercise, consider keeping your pump on the Activity setting to reduce the risk of delayed lows.
  
  

Important Reminders for Exercise with Diabetes

• Avoid Heavy, Fatty Meals Before Exercise: Meals high in fat or protein can take longer to digest, which may cause nausea or cramping during exercise.
  
  
• Timing Is Crucial: Eat your pre-workout snack about 60–120 minutes before starting your session. This ensures you have time to digest and stabilize your blood sugar.
  
  
• Be Ready for the Unexpected: Whether you’re doing cardio, strength training, or yoga, blood sugar responses can be unpredictable. Track your trends, stay prepared, and communicate with those around you (especially a workout buddy) about potential fluctuations.
  
  

Conclusion

Exercise can be one of the most powerful tools for managing blood sugar, but it requires personalized adjustments. Factors like time of day, fitness level, activity type, and insulin timing all play significant roles. By paying attention to these variables and tracking your trends, you can make more informed decisions about how to exercise safely and effectively. Whether you're tackling a morning jog, an afternoon strength training session, or a calming yoga class, staying intentional, prepared, and informed will set you up for success in managing your blood sugar.

You’ve got this.

Stay fun,

Madi Cheever, MPH, RD, LDN, CHES
Type One Type Fun

‼️DISCLAIMER: although I am a healthcare professional, this post is not intended to be medical advice. This is simply me sharing some of what I know, but your body may not respond in this way so please make sure you are chatting with your diabetes educator and/or doctor first ‼️ or bring me onto your care team 😘