Regular physical activity is one of the most effective ways to improve overall health and manage diabetes. Exercise can help lower blood sugar, improve insulin sensitivity, support heart health, increase strength, and improve mood.
At the same time, exercise can sometimes cause blood sugar to rise—or increase the risk of low blood sugar. These different responses can be confusing, especially if you're new to diabetes. The good news is that once you understand how your body responds to different types of activity, you'll be better prepared to exercise safely and confidently.
Why Exercise Changes Blood Sugar
Your muscles need energy to move. During exercise, they use glucose from your bloodstream as well as glucose stored in your muscles. As your muscles work, they often become more sensitive to insulin, allowing glucose to move into cells more efficiently.
For many people, this causes blood sugar to decrease during or after exercise. However, not every workout affects blood sugar the same way.
Different Types of Exercise Can Have Different Effects
The way your blood sugar responds depends on the type, intensity, and duration of the activity.
Aerobic exercise
Aerobic activities involve continuous movement over a longer period — walking, jogging, cycling, swimming, hiking, dancing. These activities often lower blood sugar because muscles continuously use glucose for energy. People taking insulin or medications that can cause hypoglycemia may be more likely to experience low blood sugar during or after prolonged aerobic exercise.
Strength training
Strength training includes weightlifting, resistance bands, bodyweight exercises, and weight machines. Blood sugar may decrease during strength training, remain stable, or even rise temporarily depending on the intensity of the workout and your individual response. Over time, building muscle improves insulin sensitivity and supports long-term glucose management.
High-intensity exercise
Short bursts of intense activity — sprinting, high-intensity interval training (HIIT), competitive sports, heavy lifting — can sometimes cause blood sugar to increase temporarily. During intense exercise, your body releases stress hormones like adrenaline, which stimulate the liver to release additional glucose into the bloodstream. For most people, this increase is temporary.
Exercise Can Continue Affecting Blood Sugar After You Finish
One of the most important things to remember is that exercise doesn't stop affecting your glucose when your workout ends. Your muscles continue replenishing their energy stores for several hours afterward, which means blood sugar may continue to decrease well after physical activity has ended.
For people using insulin or certain diabetes medications, delayed hypoglycemia may occur several hours after exercise, sometimes overnight. Understanding this possibility can help you and your healthcare provider develop a safe exercise plan.
How a Continuous Glucose Monitor Can Help
If you use a continuous glucose monitor (CGM), it can provide valuable insight into how your body responds to different activities. You may notice gradual decreases during long walks, temporary increases during intense workouts, overnight glucose changes after afternoon or evening exercise, and how quickly your glucose recovers afterward. Over time, these patterns help you understand your own unique response to exercise.
Check Before You Exercise
Depending on your treatment plan, your healthcare provider may recommend checking your glucose before beginning physical activity. Knowing your starting glucose — and your trend arrow, if you use a CGM — can help you decide whether it's safe to exercise immediately or whether you should follow your diabetes management plan first.
The recommendations vary depending on your type of diabetes, your medications, your planned activity, and your overall health. Follow the guidance provided by your healthcare team.
Be Prepared for Low Blood Sugar
If you take insulin or medications that can cause hypoglycemia, always be prepared. Carry a fast-acting source of glucose, such as glucose tablets, glucose gel, regular (non-diet) soda, or fruit juice.
Know the symptoms of hypoglycemia: shaking, sweating, hunger, rapid heartbeat, confusion, dizziness. If you develop symptoms, stop exercising and follow your diabetes treatment plan.
Stay Hydrated
Physical activity increases fluid loss through sweating. Dehydration can affect blood sugar and make it more difficult to exercise safely. Drink water before, during, and after exercise, especially in hot weather or during longer workouts.
Wear Proper Footwear
People with diabetes should pay close attention to foot health. Choose comfortable, well-fitting athletic shoes and moisture-wicking socks. After exercise, check your feet for blisters, cuts, redness, and areas of irritation. Treating minor foot problems early can help prevent more serious complications.
Exercise During Illness
If you're sick, your blood sugar may respond differently than usual, and illness increases the risk of dehydration. If you have fever, vomiting, significant dehydration, or moderate or large ketones (if you've been instructed to check), talk with your healthcare provider about whether you should postpone vigorous exercise until you're feeling better. See our sick-day rules guide.
Building an Exercise Routine
You don't need to become an athlete to benefit from physical activity. Many people start with simple activities such as walking after meals, gardening, riding a bicycle, water aerobics, light resistance training, stretching, or chair exercises.
The best exercise is one you enjoy and can continue over time. Consistency is more important than perfection.
Frequently Asked Questions
Why does my blood sugar sometimes go up during exercise?
High-intensity exercise can trigger the release of stress hormones that temporarily increase glucose production by the liver. This response is normal and often resolves after recovery.
Can exercise cause low blood sugar?
Yes. Exercise may lower blood sugar during activity or for several hours afterward, particularly in people taking insulin or certain diabetes medications. Your healthcare provider can help you develop a plan to reduce this risk.
Is walking good for diabetes?
Yes. Walking is an excellent form of exercise for many people with diabetes. It is low-impact, accessible, and can improve blood sugar control, cardiovascular health, and overall fitness.
Should I exercise if my blood sugar is high?
It depends. The answer varies based on how high your blood sugar is, whether you have ketones, how you feel, and your type of diabetes. If you're unsure, follow your healthcare provider's recommendations before exercising.
When Should You Contact Your Healthcare Provider?
Contact your healthcare provider if you frequently develop low blood sugar during or after exercise, your blood sugar consistently rises dramatically with exercise, you're unsure how to adjust your activity safely, you're beginning a new exercise program and have diabetes-related complications, or you experience chest pain, severe shortness of breath, or dizziness during exercise.
Seek Emergency Medical Care If
Seek immediate medical attention if you experience severe hypoglycemia requiring assistance from another person, loss of consciousness, a seizure, chest pain, severe shortness of breath, or symptoms of diabetic ketoacidosis (persistent vomiting, rapid breathing, confusion, or severe dehydration).
Tips for Exercising Safely With Diabetes
Stay consistent with your activity whenever possible, wear a medical identification bracelet if recommended, carry a fast-acting source of glucose, stay hydrated, wear appropriate footwear, monitor your glucose according to your treatment plan, and pay attention to how different activities affect your blood sugar. Learning your body's response takes time, and it's normal for different types of exercise to produce different glucose patterns.
The Bottom Line
Exercise is one of the most powerful tools for managing diabetes and improving overall health. While physical activity often lowers blood sugar, some forms of exercise may temporarily raise glucose levels, especially during intense workouts.
Understanding how your body responds to different types of exercise, monitoring your glucose as recommended, and being prepared for both high and low blood sugar can help you stay active safely. With experience, exercise becomes more predictable, allowing you to enjoy its many health benefits with greater confidence.