Managing Blood Sugar Before, During, and After Exercise

Exercise is one of the best ways to support your health. It can help you manage your blood sugar, boost your mood, and improve your fitness. But, as many in our Glucology community know, physical activity can sometimes make your blood sugar levels unpredictable. The good news? With a little planning and regular monitoring, you can move with confidence and get the most out of every workout. 

BEFORE YOU BEGIN: CHAT WITH YOUR HEALTHCARE PROFESSIONAL

Before diving into a new fitness routine, it’s important to check in with your healthcare professional. Exercise can sometimes lead to hypoglycaemia (low blood sugar), particularly for people using insulin or certain diabetes medicines that can lower your blood sugar. Your healthcare professional can help you find the right balance between your medication, food, and physical activity, so you can exercise safely and confidently.

Questions to ask your healthcare professional:

• How might the activities I want to try affect my blood sugar?
• When is the best time of day for me to exercise?
• Will my diabetes medicines need adjusting as I become more active? Should I change my food intake before exercise?

1. BEFORE YOU EXERCISE: SET YOURSELF UP FOR SUCCESS

Why check before you move?
Exercise can sometimes lower your blood sugar, especially if you use insulin or certain diabetes medications. For some, it might even cause a short-term spike. Knowing your starting point helps you avoid unexpected highs or lows.

What to do:

• Talk to your healthcare professional before starting a new routine, especially if you’re new to exercise or changing your medication.
• Check your blood sugar 15–30 minutes before you start, especially if you take insulin or medications that can cause lows.
• Know your safe range:
  • If your blood sugar is below 5.0 mmol/L (90 mg/dL), have a small snack with 15–30g of carbs (think: fruit, crackers, or Glucochews).
  • If it’s very high (over 15 mmol/L or 270 mg/dL), check for ketones (especially if you have type 1 diabetes). If ketones are present, avoid exercise until your levels are safe.

Tip: If you’re using a continuous glucose monitor (CGM), check with your healthcare team about the best monitoring approach for you.

2. DURING EXERCISE: STAY AWARE AND LISTEN TO YOUR BODY

Why monitor while moving?
Exercise can lower your blood sugar, sometimes quickly. This is especially true for longer or more intense sessions, or if you’re trying a new activity.

What to do:

• Check your blood sugar every 30 minutes during longer or unfamiliar workouts, especially if you’re new to exercise or adjusting your routine.
• Watch for symptoms of low blood sugar, Shakiness, dizziness, sweating, weakness, or confusion. If you feel any of these, stop and check your levels right away.
• Have fast-acting carbs ready, If your blood sugar drops below 3.9 mmol/L (70 mg/dL), treat with 15g of quick carbs(4 tablets of Glucochews), wait 15 minutes, and recheck.

Remember: If you’re doing outdoor activities or playing sports, keep your supplies handy and let someone know about your diabetes if possible.

3. AFTER EXERCISE: KEEP AN EYE OUT FOR DELAYED LOWS

Why check after you finish?
Your muscles keep using glucose to refuel after exercise, which can lead to delayed lows, even hours later.

What to do:

• Check your blood sugar as soon as you finish and again a few hours later, especially after intense or long sessions.
• Have a balanced snack with slower-acting carbs (like a granola bar or trail mix) if you’re at risk of dropping low.
• Stay alert for symptoms of low blood sugar for up to 8 hours after exercising.

A FEW EXTRA TIPS FOR SAFER, HAPPIER MOVEMENT

• Hydrate well before, during, and after your workout.
• Wear supportive shoes and check your feet after activity.
• Keep a log of your exercise, blood sugar readings, and how you felt—this helps you spot patterns and adjust as needed.
• Celebrate every effort! Movement is a win, no matter how small.

Exercise is a powerful tool for managing diabetes, but everyone’s body reacts differently. Before starting a new exercise routine or making significant changes, always check in with your healthcare professional. They can help you find the safest approach for your unique needs.

1. How does exercise affect blood sugar levels in people with diabetes?
Exercise can help lower blood sugar levels by improving insulin sensitivity and helping your muscles use glucose for energy. However, depending on the type, intensity, and duration of exercise, blood sugar may also temporarily rise or fall, making regular monitoring important.

2. What should my blood sugar level be before exercising?
Before exercising, it’s recommended to check your blood sugar 15–30 minutes beforehand. If your blood sugar is below 5.0 mmol/L (90 mg/dL), you may need a small carbohydrate snack. If levels are very high (over 15 mmol/L or 270 mg/dL), especially with ketones present, it’s best to avoid exercise until levels are safe.

3. How often should I check my blood sugar during exercise?
For longer or unfamiliar workouts, checking your blood sugar every 30 minutes is recommended. Monitoring during exercise can help prevent hypoglycaemia and allow you to respond quickly if your levels drop.

4. Can exercise cause low blood sugar after a workout?
Yes. Blood sugar can continue to drop for several hours after exercise because muscles use glucose to recover and refuel. Delayed hypoglycaemia may occur up to 8 hours later, so checking your blood sugar after exercise and later in the day is important.

5. What are the best safety tips for exercising with diabetes?
Some important exercise safety tips for people with diabetes include staying hydrated, carrying fast-acting carbohydrates, wearing supportive footwear, monitoring blood sugar before, during, and after exercise, and speaking with your healthcare professional before starting a new fitness routine.

Explore our blog for more tips and resources on diabetes and exercise.

Disclaimer: This blog is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your doctor or a qualified health provider with any questions about your condition. If you have a medical emergency, call 911 (US) or 000 (Australia) immediately, or visit your nearest emergency care center.