A key adverse effect of insulin therapy is low blood glucose or hypoglycaemia – also known as a ‘hypo’.

Hypoglycaemia occurs when blood glucose falls below 4mmol/L. It can result from administering too much insulin or not having a good balance of food intake and insulin treatment. Exercise, alcohol on an empty stomach and delaying or missing meals without adjusting insulin dosing in relation to food intake can make people more vulnerable to hypoglycaemia.

Insufficient food consumption has been shown to be the most likely cause of a hypo. Early symptoms include sweating, fatigue, tingling of the lips, turning pale, trembling or shaking, palpitations and dizziness. Other symptoms include:

• Headache
• Feeling hungry and/or irritable
• Blurred vision
• Slurred speech
• Confusion or disorientation.

An example of a patient’s description is: “When it’s low, I feel jittery. I might shake, I can’t see properly and I can’t concentrate then either. But although that’s exactly what I need to do (eat something), I rarely feel hungry – that comes afterwards.”

Patients need to act quickly by testing their blood glucose, where possible, and treating the hypoglycaemia immediately to avoid further deterioration, which can result in convulsions, loss
of consciousness and coma. People receiving insulin should always carry with them a fast-acting source of glucose.

Insulin requirements usually increase during illness or infection and patients should be advised to monitor their blood glucose more often and adjust their insulin doses appropriately during this time. This is known as the Sick Day Rules.