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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.
It’s important to be aware that exercise can impact blood glucose levels in various ways:
| Time | During Exercise | 12 to 24 hours after completion of exercise |
|---|---|---|
| Effect on glucose | Glucose may fall or rise depending on type and duration of exercise. | You are more sensitive to insulin. You may be at risk of hypoglycemia at night especially if you exercise late in the day. |
Different types of physical activity can have varying effects on your blood glucose levels (Table 1).
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 involves bursts of intense exercise alternated with recovery or low-effort periods. This includes activities like HIIT work-outs or intervals of sprinting and cycling.
Very intense HIIT exercise can lead to a rise in blood glucose due to the release of stress hormones. During these activities, you may also experience symptoms that mimic hypoglycaemia like sweating, palpitations and giddiness. A blood glucose check will help you distinguish these exerciserelated symptoms from true hypoglycaemia.
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 .
While the typical responses are outlined in Table 1 below, it is important to understand that each individual’s reaction to exercise can vary. Also, there are other factors influencing glucose levels such as the amount of insulin in your body at the time of exercise and the amount of carbohydrates consumed during exercise.
This page offers general principles as a starting point. The key is to understand how your own body 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.
For short-duration, gentle exercises like a slow walk (less than 30 minutes), you may not need any additional preparation apart from bringing along some quick-acting carbohydrates to rescue hypoglycaemia.
However, the risk of hypoglycaemia during exercise increases with
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 while exercising.
1. Prepare in advance by reducing the amount of active insulin in your body during the time of exercise
| Meal-Time Insulin | If exercising within three hours after a meal, reduce your meal-time insulin dose by 50% for that meal before the exercise. If 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 a basic insulin pump*, lower your basal insulin rates approximately 1.5 to 2 hours before you start cardio exercise. |
Consult your healthcare team for how to perform the above adjustment safely. For very long-duration exercises (four hours or more), additional preparation is necessary.
If you are on an advanced hybrid closed loop pumps, you should speak to your healthcare team as the above may not apply to you.
2. Prepare your exercise kit
3. Plan to exercise with a friend or family member who can assist you in case of hypoglycaemia
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 | |
|---|---|---|
| < 4 | Avoid exercise, rescue hypoglycaemia. | |
| > 4 to 5 | Take 20g of carbohydrate* and recheck glucose before starting | |
| > 5 to 7 | Take 10g of carbohydrate* then start | |
| > 7 to 10 | Good to start | |
| >10 to 15 | OK to start, but exercise performance may be poorer | |
| >15 mmol/L | Check 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:
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 general guide, consume 15 to 30g of carbohydrates for every 30 minutes of moderate-intensity cardio exercise. For example, sipping on a bottle of isotonic drink during exercise can be effective to prevent hypoglycaemia (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. Monitoring glucose levels using a continuous glucose sensor or flash glucose monitoring sensor.
If you are wearing a continuous glucose sensor or flash glucose monitoring sensor, monitor your glucose levels frequently during exercise.
Do remember that there is a lag time between the interstitial glucose read by the sensor and your actual blood glucose.
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 |
|---|---|
| < 4 | Avoid exercise, rescue hypoglycaemia. |
| >4 - 5 | May be ok to start if you have previously noticed a predictable rise in glucose during this exercise |
| >5 to 7 | Good to start |
| >7 to 15 | OK to start, but glucose levels will rise further |
| >15 | Avoid 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).
Strategies to mitigate overnight hypoglycemia risks:
1. Less basal insulin overnight
For those using a bedtime basal insulin injection or an insulin pump, consider reducing the basal insulin dose by 20% overnight.
2. Less meal-time insulin
Post-exercise, you may require 50% less meal-time insulin for the same amount of carbohydrates consumed.
3. You may need less insulin to correct high blood glucose levels
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 before bed, like a sandwich. 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:
