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Exercise and Insulin Dependence

Nina Ghamrawi, MS, RD, CDE
August 1, 2023
April 30, 2024

Managing regular exercise is challenging, regardless of your condition. But those with a risk of low blood sugars may find fitting exercise into their routine to be downright scary. Between figuring out medication dosing, or the timing of meals, exercise and glucose checks, exercising with Diabetes can become confusing, and preventing low glucose when you take insulin or glucose-lowering medications is a delicate balance.

In type 2 Diabetes, which is more common, the body either resists the effects of the insulin that it makes, or it does not make enough insulin. People with type 2 typically have trouble bringing glucose down from a high. But with Type 1 Diabetes, the body does not make insulin at all. For both groups of patients, diet and exercise are important to help prevent complications, especially in children and young adults with type 1. When we exercise, our blood sugars can decrease. But when we are taking medications that can also cause low blood sugars, exercise can potentially push glucose levels to dangerously low levels, or cause glucose to be less controlled.

Standard Exercise Recommendations

The American Dietetics Association has some standard recommendations for exercise:

Children and adolescents should

  • Exercise for 60 minutes or more every day, including moderate or vigorous intensity aerobic activity, and
  • Also do muscle strengthening and bone strengthening activities 3 days per week

Most adults should

  • Do 150 minutes or more of exercise per week, divided between at least 3 exercise days per week
  • Have no more than 2 days in a row without exercise
  • Also do strength training exercises 2-3 times per week on alternating days
  • Do flexibility and balance training, especially for older adults, at least 2-3 times per week.

Regarding Diabetes, insulin, and exercise recommendations, there is a Diabetes and Endocrinology consensus statement published in 2017 that identifies some key details when dealing with glucose management for people with Type 1. We will summarize some of the findings here.

Know Your Risks during Exercise

Research has shown that different types of exercise, time of day, and also intensity can all affect the body’s glucose response. Here are some examples:

  • Aerobic exercise can lead to lower blood glucose and increased risk of low blood sugars.
  • Aerobic exercise while fasting, or extremely vigorous physical activity could lead to higher blood sugars after exercise.
  • Afternoon resistance or strength training could lower glucose levels in the afternoons, but when done in the morning has tend to increase or not change blood glucose.
  • Extremely vigorous physical activity lowers blood sugars immediately.

Regardless of the exercise, low blood sugars can develop within just 45 minutes after a workout. Also, the risk for low blood sugars is higher for the next 24 hours after a workout. With afternoon and evening strength-training exercises, the risk for low blood sugars while you sleep is higher, and also most risky.

How to Troubleshoot Insulin and Minimize Glucose Extremes

Insulin and Medication Dosing to Prevent Lows:

  • If you plan to exercise after a meal, talk to your doctor about if and how much to reduce your pre-meal insulin.
  • If you often get morning lows, and you workout regularly, you may need a reduction in your long-acting insulin, glucose-lowering oral medications, or an adjustment in your post-workout or bedtime snacks.
  • Talk to your doctor to help you adjust insulin dosing more appropriately if you have a regular exercise routine.

Timing of Insulin, Meals, and Exercise:

  • Make sure you time your exercise to be 1hr or more before after when your insulin is expected to peak.
  • If your insulin is expected to peak during your workout, stop mid-workout to check your glucose if necessary, and take a mid-workout snack containing carbs. If your insulin activity is at its peak during your workout, you risk a double-effect of glucose lowering, which could be dangerous.
  • Plan your meals and snacks ahead of time, accounting for how much extra snack you may need for your workout.
  • If you are doing an evening workout, and you ate dinner containing carbohydrates within the last 2 hours, you probably don’t need a pre-workout snack - the carbs from dinner are probably enough. Instead, snack during or after to prevent glucose from going too high or too low.

Checking Glucose

  • Assess how different types of exercise affect your body differently, by monitoring glucose before and also 30 minutes after the workout.
  • Plan to check glucose before every workout.
  • If your workout spans more than 1 hour, you should check glucose half-way through the workout to protect yourself against lows.
  • Check glucose during the workout if the workout is extra intense, or you are feeling low

Always take your glucose testing supplies with you, and be prepared to use them during a workout if needed. Always have a snack prepared to take in the middle of a longer workout.

Preventing Lows with the Best Snacks

A perfect snack to provide the most carb-steady energy that lasts through the whole workout and doesn’t have irregular glucose peaks should be consumed 30-60 minutes before a workout. Some example could be:

  • 1-2 whole grain carbohydrate servings (around 15-30g total carbohydrate), with
  • Healthy protein, around 1oz (approx. 7g protein), and
  • Healthy fats, around 5-10g total fat


Whenever possible, talk to your Diabetes Educator and your doctor to help you troubleshoot your workouts, snack routine, and blood glucose regimen. Also talk to your doctor about what types of exercise are best for your levels of mobility, heart health risks, and general health needs. The more your glucose fluctuates between extreme highs and extreme lows, the damage may be caused over time. Most importantly, remember: the best glucose level is a steady, consistent glucose level.

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