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Exercising With Type 1 Diabetes


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Regular exercise is important for maintaining health and fitness, especially for individuals living with Type 1 diabetes. Engaging in physical activity offers multiple benefits, including improved cardiovascular fitness, enhanced muscle strength, better overall wellbeing and an improved quality of life.  

Before embarking on your exercise plan


It’s important to be aware that exercise can impact blood glucose levels in various ways: 

  • Risk of hypoglycaemia: Exercise can lead to hypoglycaemia (low blood sugar), both during and after physical activity. The likelihood of experiencing hypoglycemia increases with certain types of exercise (see below) and longer durations. Additionally, the risk may persist up to 24 hours post-exercise.  
  • Temporary glucose increase: Some forms of intense exercise, such as high-intensity interval training (HIIT), weightlifting or sprinting, can cause a temporary rise in blood glucose levels. However, similar to the risk of hypoglycemia, individuals may experience a heightened risk of low blood sugar in the 24 hours following these intense activities. 

Effect on glucose during exercise


Different types of physical activity can have varying effects on your blood glucose levels (Table 1). 

Cardio or Aerobic Exercise

These include activities like jogging, cycling, or swimming that involve repetitive movements of large muscle groups. 

Blood glucose levels typically drop during cardio exercises. The longer and more intense the workout, the more significant the drop. 

The risk of hypoglycaemia is higher with cardio exercises, especially for sessions lasting more than 30 minutes or if quick-acting insulin was administered in the three hours prior to exercising. 

Read on for tips to prevent hypoglycaemia during such exercises. 

HIIT activities (high-intensity interval training) 

HIIT involves bursts of intense exercise alternated with recovery or low-effort periods. This includes activities like running and cycling. 

Very intense HIIT sessions can lead to a rise in blood glucose due to the release of stress hormones. During these activities, symptoms like sweating, palpitations and giddiness may mimic hypoglycaemia. Monitoring your blood glucose is essential to distinguish these exercise-related symptoms from true hypoglycaemia. 

Resistance exercise or strength training 

These activities involve muscle contraction against resistance, such as weight training.  

Resistance exercises typically cause a slight increase in glucose levels if heavy loads are used. However, with light loads and repetitive exercises, blood glucose levels may decrease . 

Each individual person's response may be different 

While the typical responses are outlined in Table 1 below, it is important to understand that each individual’s reaction to exercise can vary. Factors influencing glucose levels include the amount of insulin in your body at the time of exercise and your carbohydrate intake. 

This information sheet offers general principles as a starting point. 

The key is to understand how your own body specifically responds to different types of exercise and durations.  

Monitoring your glucose trends during and after exercise is the best way to learn. This enables you and your healthcare team to devise an individualised plan for safe exercise.  

Using flash glucose monitoring or a continuous monitoring sensor is beneficial in tracking your glucose levels during exercise. It can also guide carbohydrate intake to prevent hypoglycaemia, 

Finding the right balance may require several iterations of trial, observation, review and adjustment.

Types of exercise and their impack on glucose levels during exercise


For short-duration, gentle exercises like a slow walk (less than 30 minutes), carrying quick-acting carbohydrates for hypoglycaemia rescue may suffice. 

However, the risk of hypoglycaemia increases with 

  • Longer durations of exercise (more than 30 minutes) 
  • More intense activities (e,g., cycling, running, prolonged hiking) 

Here are FIVE general precautions to prevent hypoglycaemia during and after exercise. 

These precautions are primarily for cardio exercises but can also be applied to other types of exercise where glucose drops have been observed. 

FIVE general precautions you can take to prevent hypoglycaemia during and after exercising

1) Before a planned exercise session

1.       Adjust insulin dosage 

Meal-time insulin



If exercising within three hours after a meal, reduce your meal-time insulin dose by 50%. 


However, ifi exercising more than three to four hours after a meal, consume a meal with low glycaemic index carbohydrates and administer your usual amount of meal-time insulin dose.



Basal insulin


For those using an insulin pump, lower yourbasal insulin rates approximately1.5 to 2 hours before you start cardio exercise. 


If you are on basal insulin injections, consider reducing your basal insulin dose prior to exercise. 


Consult your healthcare team for safe adjustment methods. 

For very long-duration exercises (four hours or more), additional preparation is necessary. 

2.       Prepare your exercise kit 

  • Ensure you have a glucometer with test strips and lancets, or if using a glucose sensor, bring the reader/phone 

  • Carry quick-acting carbohydrates, such as glucose tablets, sweets or a sweet drink, for treating hypoglycaemia 

  • For exercise sessions longer than 30 minutes, prepare a carbohydrate-rich snack to maintain glucose levels 

3.       Plan to exercise with a friend or family member who can assist you in case of hypoglycaemia 

2)    At the start of exercise: Start with a good pre-exercise glucose level 

An ideal glucose level before starting exercise is between 7 to 10 mmol/L. 

(These targets might be adjusted by your healthcare team based on your individual risk of hypoglycaemia.) 

Blood glucose level before cardio exercise (mmol/L)Action to take before beginning cardio exercise
< 4Avoid exercise, rescue hypoglycaemia.
>4 to 5Take 20g of carbohydrate* and recheck glucose before starting
>5 to 7Take 10g of carbohydrate* then start
>7 to 10Good to start
>10 to 15OK to start, but exercise performance may be poorer
>15 mmol/LCheck ketones and consider postponing exercise, especially if ketones are elevated.

*Do not take additional insulin to cover these carbohydrates. Examples of 10g quick-acting carbohydrates: 

  • 200ml of isotonic drinks (not sugar free)
  • 3 glucose tablets
  • ½ packet of carbohydrate energy gels
  • One small banana

3)    During exercise 

1.       Carbohydrate replenishment 

Aim to replenish carbohydrates every 30 to 60 minutes during cardio exercise. The amount required varies from 0.5 to 1 gram/kg body weight/hour of exercise, depending on the intensity. Higher intensity or failure to reduce insulin doses in advance will increase carbohydrate needs. 

As a guideline, consume 15 to 30g of carbohydrates for every 30 minutes of moderate-intensity cardio exercise. For example, sipping on a bottle of isotonic drink can be effective (500ml of isotonic drink typically contains approximately 30g of carbohydrates). 

2 Adding short bursts of high-intensity activity during cardio, such as intermittent sprinting while jogging, can help elevate blood glucose levels 

3.       If hypoglycaemia occurs, stop exercising immediately 

4.       Frequently monitor glucose levels if using a continuous glucose sensor or flash glucose monitoring sensor. Be aware of the lag time between the sensor reading and actual blood glucose. 

  • Start consuming carbohydrates when the sensor shows glucose levels falling below 7 mmol/Lwith a downward trend 
  • If the sensor reading drops to 5 mmol/L or below with downward trend, stop exercising and consume carbohydrates to prevent hypoglycaemia 
  • If experiencing hypoglycaemia symptoms but your CGMS does not reflect this, perform a capillary glucose check for accuracy. 

4)   Immediately after exercise 

If your blood glucose is moderately high post-exercise, refrain from administering correction insulin. Instead, continue monitoring your levels, as the elevation is often temporary.  


Exercises such as HIIT, interval sprints or weightlifting typically elevate blood glucose due to the release of stress hormones. These activities carry a lower risk of hypoglycaemia. 

Check your blood glucose levels before starting. An ideal starting glucose level is between 5 to 7 mmol/L. 

Blood glucose level before HIIT/resistance exercise (mmol/L)Action to take before beginning exercise
< 4Avoid exercise, rescue hypoglycaemia.
>4 - 5May be ok to start if you have previously noticed a predictable rise in glucose during this exercise
>5 to 7Good to start
>7 to 15OK to start, but glucose levels will rise further
>15Avoid exercise

After high-intensity workouts, if blood glucose is moderately high, avoid correction insulin and continue to monitor levels.  


Post-exercise, insulin sensitivity may increase, elevating the risk of hypoglycemia for the remainder of the day or night (up to 12 to 24 hours). This risk is present regardless of the type of exercise performed (cardio, HIIT or resistance exercises). 

Preventing nocturnal hypoglycaemia after exercise. 

Strategies to mitigate overnight hypoglycemia risks: 

1.       Adjust basal insulin. 

For those using a bedtime basal insulin injection or an insulin pump, consider reducing the basal insulin dose by 20% overnight. 

2.       Meal-time insulin reduction 

Post-exercise, you may require 50% less meal-time insulin for the same amount of carbohydrates consumed. 

3.       Modifying insulin correction factors 
Exercise caution when correcting high blood glucose levels post-exercise, especially before sleeping, due to the increased risk of nocturnal hypoglycaemia. Consult your healthcare team about adjusting your insulin sensitivity factor and/or glucose target for the post-exercise period. 

4.       Pre-bedtime blood glucose check 

Ensure you check your blood glucose levels before going to bed. 

5.       Consider having a slow-acting carbohydrate snack,like a sandwich, before bed. Avoid administering meal-time insulin for this snack. 


Stay well-hydrated with water during exercise 

For safety, exercise with a friend or family member, especially if there is a risk of hypoglycaemia 

Regularly check your glucose before, during and after exercise 

Postpone exercise if: 

  • Glucose levels are below 4.0 mmol/L or above 15.0 mmol/L before starting 
  • Ketones are present 
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