Exercise, stress, illness: What causes blood glucose readings to swing?

Thursday, 27 May 2021

Just like the scores in professional team sports, blood glucose levels can swing in a matter of moments.

While living with diabetes isn’t a sport, the day to day challenges with diet, exercise, insulin adjustments and the stresses of daily life can certainly make it feel like a marathon.

Life isn’t always perfect; however, being aware of the factors that can influence our glucose levels helps.

What causes blood glucose readings to rise?

For some readers these influences may be common knowledge. Others might find this information changes the way you manage your diabetes.

When we’re stressed the body releases glucose to ensure there is enough energy available for our body to cope.

Our sympathetic nervous system is primarily responsible for the fight or flight response whereby our bodies secrete adrenaline, causing glucose to be released from the liver, insulin levels to rise and glucagon levels to fall.

This is a physiological response to ensure we have enough energy to escape potentially dangerous or serious situations.

Energy for fight or flight

In the short term we might notice a spike in our glucose levels; however, this shouldn’t last and generally isn’t a cause for concern. However, do we need this energy all the time?

The answer is no.

If we’re dealing with chronic stress this can lead to longer term challenges with managing our long-term measure of blood glucose (glycosylated haemoglobin HbA1c), This in turn increases the risk of developing diabetes-related complications.

You may have even noticed after a strenuous bout of exercise that your glucose levels were elevated.

Improved insulin sensitivity

Don’t let this impede your efforts to become more physically active. In fact, exercise will help you reap the rewards of improved insulin sensitivity.

Resistance training or other structured exercise performed at high intensities requiring substantial physical exertion can also cause a transient rise in blood glucose levels for similar reasons as those listed above.

Furthermore, if you become ill or suffer an infection, a stress response is also provoked whereby hormones such as adrenaline and cortisol work against the action of insulin, increasing blood glucose levels.

Carbohydrate content in meals

Similarly, if insulin adjustments are made and not matched to the carbohydrate content in meals or increasing levels of physical activity, you may also find your blood glucose levels swing to either side of the scale.

For this reason it’s always important to speak with your Credentialled Diabetes Educator to better understand and/or make the needed adjustments.

Remember that your HbA1c is a two to three month average of your blood glucose levels while your monitor will give you a quick snapshot of where you are at that given moment in time, which is likely to fluctuate.

Regular blood tests can give you a better idea of how things are tracking in the long term.

Top Tips

  • Aim for a moderate intensity for aerobic exercise using the talk test as a guide
  • Avoid exercising if you feel sick or unwell
  • Try managing chronic stress through simple strategies like 5-10 minutes of daily mindfulness meditation
  • Call the NDSS Helpline 1800 637 700 to speak with a Psychologist about other potential strategies to mitigate stress, or our Exercise Physiologist regarding solutions to better manage your diabetes through physical activity.


By Hayden Kelly

Diabetes NSW & ACT Accredited Exercise Physiologist


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