Stress Hyperglycaemia

Stress hyperglycaemia is a transient rise in blood glucose during acute illness, injury or surgery in a person without previously known diabetes, caused by the stress response: raised cortisol, adrenaline, glucagon, growth hormone and inflammatory cytokines that increase hepatic glucose output and cause temporary insulin resistance. It resolves when the illness settles, but it marks higher risk of complications and of later diabetes.

• Typical definition: glucose above 7.8 mmol/L (140 mg/dL) fasting or random during acute illness, with an HbA1c below 48 mmol/mol (6.5 percent). A value of 11.1 mmol/L (200 mg/dL) or more with a normal HbA1c is also stress hyperglycaemia.
• Common triggers: infection and sepsis, myocardial infarction, stroke, trauma, burns, major surgery, pancreatitis, acute asthma and chronic obstructive pulmonary disease exacerbations (steroids), critical illness, and parenteral feeding.
• Prevalence in hospital patients is about 30 to 40 percent, higher in intensive care.
• Prognosis: raised risk of infection, longer admission and death; about 30 to 50 percent develop diabetes within 5 years after hospital discharge, so follow up testing is needed.
• Children: occurs in febrile illness and with seizures. Risk of later type 1 diabetes is higher if autoantibodies are present.

• Usually no symptoms specific to hyperglycaemia; thirst, polyuria and fatigue may be masked by the primary illness.
• Features of the underlying cause: fever, chest pain, focal neurology, trauma, abdominal pain.
• Signs of dehydration with glucose above 15 mmol/L.
• Ask for a past history of prediabetes, gestational diabetes, steroid use, family history and previous abnormal glucose.

• Venous or capillary glucose; repeat when stable. Check ketones if glucose exceeds 11 mmol/L, if unwell, in children, or if the patient is on an SGLT2 inhibitor.
• HbA1c at admission differentiates stress hyperglycaemia (normal HbA1c below 48 mmol/mol) from previously unrecognised diabetes (HbA1c 48 mmol/mol or more). HbA1c is unreliable after anaemia, bleeding, transfusion, haemoglobinopathy and in pregnancy.
• Urea, electrolytes, creatinine, osmolality, blood gases, lactate and full blood count as the illness requires.
• Medicines review: steroids, vasopressors, beta agonists, antipsychotics, thiazides, tacrolimus.
• Fasting glucose or HbA1c at 4 to 12 weeks after recovery (a 75 g oral glucose tolerance test is more sensitive), and then annually for the first years.
• Differentials: new type 1 or type 2 diabetes, diabetic ketoacidosis or hyperosmolar state, steroid induced diabetes, pancreatic disease, endocrine causes (Cushing syndrome, phaeochromocytoma, thyrotoxicosis, acromegaly).

Treat the cause (infection, ischaemia, pain, volume depletion), and correct dehydration.

Hospital targets

• Glucose 7.8 to 10 mmol/L (140 to 180 mg/dL) in most patients; avoid values below 5.6 mmol/L.
• Persistently above 10 mmol/L on two readings 2 hours apart: start insulin, usually subcutaneous basal insulin (glargine 0.1 to 0.2 units/kg once daily) with correction doses, or an intravenous insulin infusion in critical illness, myocardial infarction, stroke or perioperative care. Titrate by capillary glucose every 1 to 2 hours (infusion) or every 4 to 6 hours (subcutaneous).
• Avoid sliding scale insulin alone, and stop insulin when glucose normalises (usually below 8 mmol/L without insulin).

Outpatient or community

• Most need no drug treatment. Advise a balanced low glycaemic index diet, avoiding sugary drinks and heavy meals, regular activity and weight loss when overweight.
• Check capillary glucose daily for 1 to 2 weeks after discharge when values were above 11 mmol/L.
• Metformin 500 mg daily, increasing weekly to 1 g twice daily, is used if hyperglycaemia persists after the illness settles and glucose is above 7 mmol/L fasting (check eGFR above 30, avoid during acute illness or dehydration).
• Stop steroid courses when possible.

Follow up

• Retest at 4 to 12 weeks, then at 6 and 12 months, and annually. Annual HbA1c is advisable for at least 5 years.
• Advise warning symptoms of diabetes and an earlier visit if they occur.

Special groups

• Pregnancy: refer for glucose tolerance testing at 24 to 28 weeks.
• Children: monitor ketones, check autoantibodies (islet cell, glutamic acid decarboxylase, insulin, zinc transporter 8) and refer to paediatric endocrinology.
• Critical illness: specialist glycaemic control in intensive care.
• Hypoglycaemia risk: older adults, kidney disease and reduced intake.