Regular exercise is a great way to manage blood glucose levels and provides many other benefits to keep us healthy. Why do glucose levels sometimes rise during exercise? Exercise can help insulin work better, lower blood pressure and cholesterol levels, reduce the risk of heart disease, decrease stress and also assists with
maintaining a healthy weight. The effect exercise has on your blood glucose levels, however, will depend on the type, intensity and duration of your chosen activity. Other variables might also include timing of medication and meals eaten before exercise. The general consensus is that exercise will lead to a reduction in blood glucose levels and help with long-term management. However, the
short-term response can vary, particularly with high-intensity exercise such as running, interval exercise or resistance training. With high-intensity exercise, there is an increase in your heart rate and the fast-paced movements cause the release of different hormones, including adrenaline. This stimulates the release of
glucose from places such as your liver to fuel this high intensity movement. As a result, you may see a short-term (over minutes to hours) increase in your blood glucose levels, but the long-term outcome (over one to two days) will bring about a sustained decrease in blood glucose levels. So, if you’ve ever experienced an increase in your blood glucose levels shortly after this type of exercise, don’t be alarmed, this is a normal
response. Alternatively, lower and moderate intensity exercise such as walking or swimming will lead to both a short-term and long-term reduction in your blood glucose levels, as this type of exercise utilises the excess glucose floating around in the bloodstream. This type of exercise is more sustainable for most people and forms part of the
National Physical Activity Guidelines with the goal of 30 minutes of moderate intensity activity on most days of the week. It’s important to become familiar with your blood glucose levels in response to exercise.High-intensity exercise can cause peaks
Become familiar with your BGLs and exercise
When starting a new exercise, it’s a good idea to check blood glucose levels before, during and after to see how your body reacts to different activities and to help with planning for future exercise sessions. By understanding your response to exercise, you can avoid adverse events such as hypoglycaemia (lows) and hyperglycemia (highs).
If your blood glucose level before exercise is over 15mmol/L, and it is unexplained, check your blood ketone levels. Mild to moderate aerobic exercise can be started if ketones are less than 0.6mmol/L. Intense exercise should be avoided, however, and it’s recommended that blood glucose levels are checked during and after exercise.
For more guidance with exercise, please see your doctor for a referral to an Accredited Exercise Physiologist.
By Hayley Nicholson
Exercise Physiologist, CDE
2020-02-05
Editor’s note: This content was originally produced by JDRF, shared here as part of the JDRF – Beyond Type 1 Alliance. You can find more valuable content about exercising with T1D in JDRF’s exercise guide.
Have you ever wondered why — with certain types of exercise — your blood sugar does not drop and sometimes even rises?
Science suggests that it may be related to the stress hormone, adrenaline, also known as epinephrine. Adrenaline is the hormone that gets produced when you push yourself or experience intense stress.
Whenever you’re doing something that requires quick bursts of energy, like sprinting, weight lifting, or martial arts, your adrenaline levels tend to rise, alongside other hormones like cortisol.
Adrenaline helps meet the body’s need for more energy by releasing more glucose into the blood. Adrenaline and cortisol can also help prevent hypoglycemia (low blood sugar) by counteracting the effects of insulin during a stressful situation.
If the effects of stress hormones are not balanced by the amount of glucose used for fuel during exercise, blood sugar levels can become too high, which can lead to dehydration as extra glucose spills into the urine.
In addition to adrenaline, other factors can lead to an unwanted rise in blood glucose.
- Eating or drinking too many carbohydrates before or during a workout.
- Overtreating a low blood sugar before or during a workout.
- Disconnecting an insulin pump so no insulin is being delivered.
- Reducing rapid-acting insulin too much at the meal or snack before a workout.
If you do experience severe high blood sugar with intense exercise or competition or if you have symptoms of a severe high like fatigue or frequent urination, there are a few things you can do.
- Drink water to keep yourself hydrated and help dilute the extra glucose in your bloodstream.
- Do a light aerobic warmup and cool down around anaerobic exercise, such as a 20 minute walk.
- If you are experiencing intense anxiety or stress around a competition or exercise event, try visualization exercises to calm your nervous system and lower the release of stress hormones.
If your glucose levels remain elevated after these approaches, consider a conservative insulin correction dose, perhaps half the amount you would normally use at the same blood glucose level. Be careful when you do this, particularly later in the day, as it may increase the likelihood of a low blood sugar level overnight.
If you have unexplained hyperglycemia (high blood sugar) during or after exercise, be sure to check for ketones. Also keep in mind that it is possible to have elevated ketones without high blood sugar, so if you’re feeling sick during or after exercise, be sure to check as well.
It is important to check for ketones if you are feeling sick, regardless of blood sugar level, because ketones, along with dehydration and electrolyte imbalance, can lead to diabetic ketoacidosis (DKA). Be sure to check with your healthcare team about how to handle ketones before you start a new exercise routine.