Exercising with Diabetes

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People with diabetes sometimes become frustrated with the short-term blood sugar fluctuations induced by exercise. However, regular physical activity is crucial for long-term cardiovascular health, joint strength and flexibility, stress management, improved insulin sensitivity, along with a wide range of other health benefits. In fact, many patients see significant improvements in their overall blood sugars once they establish a regular exercise routine. The key to minimizing those aggravating fluctuations during and after exercise will be learning by experience.  


Depending on your diabetes medications, how recently you've eaten and what you've eaten, exercise can affect your blood sugar in different ways. In fact, some patients may even experience higher sugars during exercise. The suggestions below should help get you started but again, your most powerful tool will be experience. Therefore, don't be afraid to keep a log at first if this will help you to identify patterns in your blood sugar changes.


1. Check your blood sugar before, after and during exercise when possible.   

Different activities may affect your levels in different ways so don't always assume that your blood sugar will go down. For instance, brisk walking may cause your number to fall, whereas a more competitive and adrenaline-driven activity like basketball may actually cause your number to rise. Checking your sugars before and after will empower you to make better treatment decisions for future workouts.


2. If you're experiencing lows during exercise...  

This will be most common in patients on insulin. You have a couple options on how to handle this depending on when you're exercising. 

If you're exercising within an hour of taking fast-acting insulin (Apidra, Novolog, Humalog) with a meal, it may help to reduce the amount of insulin that you're taking when you eat. Including protein in this meal will also reduce your risk for lows. 

If your exercise is not this close to your meal, try having a small snack before your workout. This snack is also a good option for patients who are experiencing lows during exercise but who are not taking insulin with their meals. As mentioned above, including protein in the snack will also reduce your risk for lows.

If you're on an insulin pump, you can also try reducing your basal rate before and during exercise rather than eating those extra calories. 


3. If you're experiencing lows (even hours) after exercise...

Troubleshooting delayed low blood sugars should be approached similar to the methods discussed above. Consider the timing of your meals and the insulin that you are taking with those meals. If you're giving insulin and eating shortly after exercise, consider reducing that mealtime insulin dose. 

If you don't typically have a meal after exercise, a small snack might help to avoid delayed lows as well. This can be particularly useful for patients who like to exercise before bed. Again, including some protein in this snack may help. If you are using an insulin pump, you may be able to avoid these extra calories by using a reduced temp basal rate during and after exercise.

Once exercise becomes a part of your daily routine, you may see your sugars running lower than usual more and more frequently. Type 1 and type 2 diabetes patients can become more sensitive to insulin with a regular exercise routine. If you begin to feel like you are eating more than you want just to avoid going low, contact your endocrinologist as you may need adjustments to your medication regimen with this new change in your sensitivity. 


4. If you're experiencing highs after exercise...

This may be due to you overcompensating prior to exercise in an effort to avoid going low. If you typically have a meal before your workout, try taking more of your regular mealtime insulin dose but increase the dose gradually (i.e. try going up on the dose only 15% at a time). If you've been having a snack with no insulin, try having a smaller snack, skipping the snack or taking a little insulin if you're still wanting to eat something before your workout. 

Keep in mind, the fewer variables the better. Consistency with the exercise duration, as well as the amount of carbohydrates that you're eating prior to the exercise will make it much easier to find patterns while you're still learning how your blood sugar responds to exercise.



It is true that physical activity can effectively lower a high blood sugar. However, under no circumstances should this method be used if you have ketones in your blood. The body produces ketones when there is not enough insulin present to let sugar pass into your cells and exercising in this condition will actually cause your body to produce more. 

Although it is much more common in type 1 diabetics, it can occur in type 2 diabetics under special circumstances as well and should be taken very seriously in both cases. We recommend that you test your urine for ketones anytime you see a fasting sugar exceeding 240 mg/dl or a daytime sugar exceeding 300 mg/dl. If you do test positive for ketones, exercise is NOT a safe treatment. Instead, drink plenty of fluids and lower your blood sugar with insulin as instructed by your endocrinologist. In the case of high ketones, notify your doctor and go to the nearest emergency room. High ketones for several hours can lead to diabetic ketoacidosis (DKA) resulting in coma and even death and must be addressed immediately.