Stress hyperglycaemia refers to a temporary rise in blood glucose during acute physical or psychological stress.
It commonly occurs during illness, injury, or surgery, when the body releases stress hormones to provide extra energy.
Although it can resemble diabetes on initial testing, blood sugar levels often return to normal once the stress resolves.
The Stress Response and Cortisol
When the body experiences stress, it activates hormonal pathways designed to maintain survival.
A key hormone in this response is cortisol.
Cortisol increases circulating glucose to ensure the brain and vital organs have sufficient energy during illness or trauma.
While protective in the short term, this response can lead to raised blood sugar levels.
How Cortisol Raises Blood Sugar
Cortisol increases glucose production in the liver and reduces the body’s sensitivity to insulin.
It also limits glucose uptake by muscle and fat tissue.
Together, these effects create a temporary state of insulin resistance, resulting in elevated blood glucose.
Other Stress Hormones
Cortisol works alongside other stress hormones, including….
- Adrenaline,
- Noradrenaline
- Glucagon
- Growth hormone.
These hormones, in addition to stimulating glucose release from the liver.
Inflammatory processes during acute illness also reduce insulin sensitivity, amplifying the rise in blood sugar.
When Stress Hyperglycaemia Becomes a Problem
A mild, short-term rise in glucose can be part of the body’s normal response to stress.
However, significant hyperglycaemia is associated with…
- Infections
- Delayed recovery
- Organ complications
- Increased mortality
Sudden glucose spikes may be particularly harmful in individuals without pre-existing diabetes.
Cortisol vs True Diabetes
Stress hyperglycaemia differs from diabetes in that it develops acutely and often resolves once the illness improves.
Diabetes, by contrast, is a chronic condition characterised by persistently raised blood glucose, even in the absence of stress.
Tests such as HbA1c help distinguish between a temporary stress response and underlying diabetes.
The stress hyperglycaemia ratio can also assist in assessing whether glucose levels are disproportionately elevated relative to baseline control.
Long-Term Risks
Although stress hyperglycaemia often settles, it is not always benign.
Individuals who experience it have an increased risk of developing type 2 diabetes in future.
This may reflect underlying metabolic vulnerability or stress-related strain on insulin-producing cells.
Follow-up testing after recovery is therefore important.
Diagnosis and Monitoring
Diagnosis cannot be made from a single elevated glucose reading.
Blood glucose results should be interpreted alongside HbA1c to determine whether hyperglycaemia is acute or long-standing.
Comparing current levels with estimated baseline control provides a clearer clinical picture.
Management
Management aims to lower blood glucose safely while avoiding hypoglycaemia.
Moderate glucose targets are generally preferred over tight control. Insulin is commonly used in acute settings due to its rapid and adjustable action.
Treating the underlying cause of stress is essential, as this reduces the hormonal drivers of high glucose.
What happens if left untreated?
Untreated stress hyperglycaemia can lead to…
- Dehydration
- Electrolyte imbalance
- Impaired immune function
- Delayed wound healing
In severe illness, uncontrolled hyperglycaemia increases the risk of complications.
Failure to reassess glucose after recovery may result in undiagnosed diabetes.
Summary
Stress hyperglycaemia is a temporary rise in blood glucose triggered by stress hormones during acute illness.
Cortisol plays a central role, supported by other hormonal and inflammation pathways.
Although it can resemble diabetes, it often resolves once the stress settles.
Appropriate testing, careful monitoring and follow-up are essential to distinguish short-term stress responses from true diabetes and to protect long-term metabolic health.
Hema, is a Specialist Dietitian at The London Obesity & Endocrine Clinic. She has helped many patients overcome weight management barriers. ©Simplyweight
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