Introduction to hypoglycaemia in patients with diabetes
Hypoglycaemia is defined as a blood glucose concentration below 4 mmol/L. However, a patient may experience symptoms of hypoglycaemia at blood glucose concentrations of more than 4 mmol/L. Symptoms are more likely to occur at lower concentrations if there have been recent episodes of hypoglycaemia, and at higher concentrations in patients in whom glycaemic targets are not achieved and those with infrequent hypoglycaemia. Hypoglycaemia can also occur without symptoms and signs, particularly in patients who have had diabetes for more than 10 years (see Hypoglycaemia unawareness for further information).
Symptoms of hypoglycaemia can be classified as:
- adrenergic (autonomic)—eg pale skin, sweating, shaking, palpitations, feeling anxious
- neuroglycopenic (due to altered brain function)—eg hunger, difficulty concentrating, confusion and inappropriate behaviour, loss of consciousness, seizures.
Hypoglycaemia can occur at any time of the day or night. The adrenergic response to hypoglycaemia is reduced during sleep, and following exercise or alcohol consumption. Continuous glucose monitoring (CGM) or self-monitoring of blood glucose concentrations (SMBG) during the night should be used for all patients with diabetes who are at risk of nocturnal hypoglycaemia.
The risk of hypoglycaemia is increased after exercise, and can last for at least 12 hours or longer after exercise, which can result in nocturnal hypoglycaemia. However, the response of blood glucose concentrations to exercise varies so patients should seek advice from their multidisciplinary diabetes team about preventing hypoglycaemia when exercising (see Physical activity and exercise for further information).
Hypoglycaemia is of particular concern in children with diabetes who are younger than 5 years. This is because young children are unable to adequately recognise and communicate the symptoms of hypoglycaemia to carers, so the hypoglycaemia is likely to become prolonged, which increases the likelihood of loss of consciousness and seizures, and subsequent brain injury.
For a list of common precipitants and patient risk factors for hypoglycaemia, see Common precipitants and patient risk factors for hypoglycaemia.
Common acute precipitants of hypoglycaemia:
- variation in carbohydrate content of food intake (eg while fasting, stopping an enteral feed)
- stopping hyperglycaemia-inducing drugs (eg glucocorticoids); see Drug-induced hyperglycaemia
- suppression of glucose production in the liver by alcohol; see Alcohol-associated hypoglycaemia
- vigorous and/or prolonged exercise
- incorrect dose or administration of insulin or long-acting sulfonylurea; see Hypoglycaemia associated with inadvertent insulin overdose and Sulfonylurea-induced hypoglycaemia.
Common and/or important patient risk factors for hypoglycaemia:
- previous severe hypoglycaemia
- hypoglycaemia unawareness
- duration of diabetes
- treatment with insulin or a long-acting sulfonylurea (eg glibenclamide, glimepiride)
- increasing age
- during pregnancy and while breastfeeding
- cognitive impairment
- kidney impairment
- liver failure
- primary gastrointestinal disease with malabsorption (eg coeliac disease)
- primary deficiencies of hormones that raise blood glucose concentration (eg cortisol [hypopituitarism, adrenal cortical failure], growth hormone [isolated growth hormone deficiency])
- previous bariatric surgery
- recent weight loss.
All patients with diabetes who are at risk of hypoglycaemia should be educated by their multidisciplinary diabetes team about ways to reduce risk of hypoglycaemia. When a patient has recovered from an episode of hypoglycaemia, consider provision of a dietary review and further education about preventing and managing hypoglycaemia if required. A patient information sheet on hypoglycaemia for adults with diabetes is available from the National Diabetes Services Scheme (NDSS) website. Information on hypoglycaemia for parents and carers of children and adolescents with diabetes is given in the parent’s manual Caring for diabetes in children and adolescents1.