A key adverse effect of insulin therapy is low blood glucose or hypoglycaemia (‘hypo’). Hypoglycaemia occurs when blood glucose falls below 4mmol/L and 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.

Patients need to act by testing their blood glucose (where possible) and treating the hypoglycaemia immediately to avoid further deterioration, which can result in extreme cases in convulsions, loss of consciousness and coma.

Early warning signs may differ from person to person and may depend on, for example, the duration of diabetes and the use of other medicines such as beta-blockers and clonidine. Those who experience hypoglycaemia without early warning signs need to monitor their blood glucose more frequently.

Mild to moderate hypoglycaemia is usually treated by eating or drinking 15-20g of a fast-acting carbohydrate (e.g. three glucose tablets or a small carton of pure fruit juice). To help restore the blood sugar and stop the levels going down again, patients should eat or drink 15-20g of a slower-acting carbohydrate such as a piece of fruit, a glass of milk or a sandwich.

Severe hypoglycaemia (where the patient may be unconscious) requires urgent treatment with glucagon administered intramuscularly or subcutaneously. The patient should be given a sugary drink or snack as soon as they are conscious, followed by a slower acting carbohydrate. An ambulance should be called if the patient has not recovered after 10 minutes of receiving the injection. Patients prescribed glucagon must check the expiry date regularly.