How to Manage Blood Sugar During Exercise for Persons with Diabetes

18 Sep 2025 By Stephen M. McMullan, M.D.

How to Manage Blood Sugar During Exercise for Persons with Diabetes

Managing blood sugar during exercise is crucial for individuals with diabetes to maintain their health and prevent complications. Exercise can have varying effects on blood sugar levels, depending on several factors such as the type, intensity, and duration of the activity, as well as individual responses. This article offers a comprehensive guide to help people with diabetes safely and effectively manage their blood sugar during exercise.

Why is Blood Sugar Management Important During Exercise?

Exercise affects the body's use of insulin and glucose. Understanding these effects is essential for preventing both hypoglycemia (low blood sugar) and hyperglycemia (high blood sugar).

Hypoglycemia: Exercise can cause blood sugar levels to drop, especially if you are taking insulin or certain diabetes medications. Low blood sugar can lead to symptoms like shakiness, dizziness, confusion, and, in severe cases, loss of consciousness.
Hyperglycemia: In some cases, especially with high-intensity exercise, the body may release stress hormones that raise blood sugar levels. Persistently high blood sugar can lead to long-term complications, such as nerve damage, kidney disease, and cardiovascular issues.

Effectively managing blood sugar levels during exercise involves careful planning, monitoring, and adjusting insulin doses or food intake as needed.

Pre-Exercise Blood Sugar Management

Before engaging in any physical activity, it is critical to check your blood sugar levels and take appropriate measures based on the results.

Blood Sugar Monitoring Before Exercise

Check your blood sugar approximately 30 minutes to an hour before you begin exercising. Here’s what you should consider: The 7 Best Foods To Stabilize Blood Sugar And Avoid Spikes

Target Range: Aim for a blood sugar level between 100 mg/dL and 250 mg/dL before starting exercise. These values can be adjusted in consultation with your healthcare provider, as individual needs vary.
Low Blood Sugar (Below 100 mg/dL): If your blood sugar is below 100 mg/dL, consume a quick-acting carbohydrate source, such as:
- 15-20 grams of glucose tablets or gel
- 4-6 ounces of juice or regular soda
- A tablespoon of honey
Wait about 15-30 minutes and recheck your blood sugar before starting exercise. If it remains low, consume another serving of carbohydrates. * High Blood Sugar (Above 250 mg/dL): If your blood sugar is above 250 mg/dL, it's essential to exercise caution. If you feel well and don’t have ketones, you might proceed with light exercise. However, avoid strenuous activities. * Check for Ketones: High blood sugar levels may indicate that your body is not producing enough insulin, leading to the production of ketones. Use a ketone testing kit (urine or blood) to check for ketones. * Avoid Exercise with Ketones: If ketones are present, do not exercise. High ketones can lead to a dangerous condition called diabetic ketoacidosis (DKA), which requires immediate medical attention. * Consult Your Doctor: If you frequently experience high blood sugar levels before exercise, discuss this with your doctor or diabetes educator. They can help adjust your medication or meal plan to better manage your blood sugar.

Adjusting Insulin or Medication Before Exercise

Depending on your pre-exercise blood sugar level and the type of diabetes medication you take, you may need to adjust your insulin dosage or medication schedule.

Insulin Users: Consult with your healthcare provider about how to adjust your insulin before exercise. Factors to consider include:
- Type of Insulin: Rapid-acting, short-acting, intermediate-acting, or long-acting.
- Dosage: How much insulin you typically take.
- Timing: When you last injected insulin.
- Exercise Intensity and Duration: The expected intensity and duration of your workout.
Your doctor may recommend reducing your insulin dose before exercise to prevent hypoglycemia. They might also suggest injecting insulin into an area that is not being actively used during exercise (e.g., the abdomen rather than the leg if you're running). * Oral Medications: Some oral diabetes medications can also increase the risk of hypoglycemia during exercise. Discuss with your doctor whether you need to adjust your medication schedule or dosage on days you plan to exercise.

| Blood Sugar Level (mg/dL) | Action | | :------------------------- | :----------------------------------------------------------------------------------------------------------------------------------- | | Below 100 | Consume 15-20 grams of fast-acting carbohydrates, recheck in 15-30 minutes. | | 100-250 | Proceed with exercise as planned. | | Above 250 | Check for ketones. If present, avoid exercise. If no ketones, proceed with light exercise, monitor blood sugar closely. |

Blood Sugar Management During Exercise

Maintaining stable blood sugar levels during exercise requires monitoring and adjustments.

Monitoring Blood Sugar During Exercise

Frequency: Check your blood sugar every 30 minutes during prolonged or high-intensity exercise.
Adjustments: If your blood sugar starts to drop, consume 15-20 grams of fast-acting carbohydrates. Recheck your blood sugar after 15-30 minutes.
Continuous Glucose Monitoring (CGM): If you use a CGM, monitor your glucose trends throughout your workout. CGMs provide real-time glucose readings and alerts for high and low levels, allowing for timely interventions.

Adjusting Food and Insulin During Exercise

Snacking: For longer workouts, plan to have snacks available to prevent blood sugar drops. Suitable snacks include:
- Energy bars
- Fruit
- Trail mix
Insulin Adjustments: Some people may need to make small adjustments to their insulin dosages during exercise to maintain stable blood sugar levels. Consult with your doctor to determine the best approach for your individual needs.

Types of Exercise and Their Impact on Blood Sugar

Different types of exercise can affect blood sugar levels differently:

Aerobic Exercise: Activities like walking, jogging, swimming, and cycling tend to lower blood sugar levels. The body uses glucose for fuel, which can reduce blood sugar.
Resistance Training: Activities like weightlifting can sometimes raise blood sugar levels, especially during the activity. This is due to the release of stress hormones that can increase glucose production. However, resistance training can improve insulin sensitivity in the long run.
Interval Training: This involves alternating between high-intensity bursts and periods of rest or low-intensity activity. Interval training can have unpredictable effects on blood sugar, so close monitoring is essential.

Post-Exercise Blood Sugar Management

After exercise, it's important to continue monitoring your blood sugar and take steps to stabilize it.

Monitoring Blood Sugar After Exercise

Immediate Post-Exercise: Check your blood sugar immediately after finishing your workout to assess its initial impact.
Delayed Hypoglycemia: Be aware that blood sugar levels can sometimes drop several hours after exercise. Check your blood sugar periodically (every 2-4 hours) for up to 24 hours after exercise, especially if you took insulin before or during your workout.
Nighttime Hypoglycemia: If you exercise in the evening, be especially cautious about nighttime hypoglycemia. Set an alarm to check your blood sugar in the middle of the night if needed.

Adjusting Insulin or Medication After Exercise

Insulin Users: You may need to adjust your insulin dosages after exercise to prevent hypoglycemia. Work with your doctor to determine the appropriate adjustments based on your individual needs and how your blood sugar responds to exercise.
Oral Medications: Some people taking oral diabetes medications may also need to adjust their medication schedule or dosage after exercise.

Replenishing Glycogen Stores

After exercise, it's important to replenish your glycogen stores by consuming a balanced meal or snack that includes carbohydrates and protein.

Carbohydrates: Help to restore glycogen levels and stabilize blood sugar. Choose complex carbohydrates like whole grains, fruits, and vegetables.
Protein: Aids in muscle repair and recovery. Good sources of protein include lean meats, poultry, fish, beans, and nuts.

Example Post-Exercise Meal

Here’s an example of a balanced post-exercise meal:

Grilled chicken breast
Brown rice
Steamed broccoli

Tips for Safe Exercise with Diabetes

Here are some general tips for safe and effective exercise management for individuals with diabetes:

Consult Your Healthcare Team: Before starting any exercise program, consult with your doctor, diabetes educator, or other healthcare professional. They can help you develop a personalized exercise plan that takes into account your individual needs and health status.
Wear a Medical ID: Always wear a medical ID bracelet or necklace that identifies you as a person with diabetes. This is especially important during exercise, in case of a medical emergency.
Carry Fast-Acting Carbohydrates: Always carry a source of fast-acting carbohydrates with you during exercise in case your blood sugar drops too low.
Stay Hydrated: Drink plenty of water before, during, and after exercise to stay hydrated. Dehydration can affect blood sugar levels and overall performance.
Choose the Right Time to Exercise: The time of day you exercise can affect your blood sugar levels. Some people find it easier to manage their blood sugar when they exercise in the morning, while others prefer exercising later in the day.
Warm-Up and Cool-Down: Always warm up before exercise and cool down afterward. This helps to gradually increase and decrease your heart rate and prepares your body for physical activity.
Listen to Your Body: Pay attention to how your body feels during exercise. If you experience any symptoms of hypoglycemia or hyperglycemia, stop exercising and take appropriate action.

Exercise Precautions

Avoid Exercising During Illness: If you are sick, especially with a fever or infection, avoid exercising. Illness can significantly affect blood sugar levels and make it more difficult to manage your diabetes.
Foot Care: If you have neuropathy (nerve damage) in your feet, take extra care to protect your feet during exercise. Wear appropriate footwear, check your feet regularly for blisters or sores, and consult with a podiatrist if needed.
Eye Health: If you have retinopathy (eye damage), avoid high-impact activities or heavy lifting, which could potentially worsen your condition.

Benefits of Regular Exercise

Despite the challenges of managing blood sugar during exercise, the benefits of regular physical activity for individuals with diabetes are undeniable. The Breakfast Formula To Prevent Mid Morning Blood Sugar Spikes

Improved Blood Sugar Control: Regular exercise can help improve insulin sensitivity and lower blood sugar levels over time.
Weight Management: Exercise can help you lose weight or maintain a healthy weight, which is crucial for managing diabetes.
Cardiovascular Health: Exercise can reduce your risk of heart disease and stroke, which are common complications of diabetes.
Mental Health: Exercise can improve your mood, reduce stress, and boost your self-esteem.
Increased Energy Levels: Regular exercise can increase your energy levels and reduce fatigue.

Conclusion:

Managing blood sugar during exercise requires careful planning, monitoring, and adjustments. By understanding how exercise affects your blood sugar levels and taking appropriate precautions, you can safely enjoy the many benefits of physical activity and improve your overall health and well-being. Always work closely with your healthcare team to develop a personalized exercise plan that meets your individual needs.