Hypoglycaemia (CBG <4mmol/L) occurs when the blood glucose level falls to values low enough to cause symptoms and signs. Significant hypoglycaemic symptoms tend not to occur until blood glucose levels below 3 mmol/l, though features such as minor cognitive disturbances may be seen at levels between 3 and 4 mmol/l.

The clinical suspicion of hypoglycaemia should be confirmed using blood or appropriate reagent sticks with, in certain circumstances, a confirmatory blood sample sent to the laboratory for subsequent assay.

If the patient is not a known diabetic on insulin or on oral hypoglycaemic agent, a blood sample should be removed and sent to the laboratory in appropriate tubes (yellow top) for later analysis of blood glucose and plasma insulin (speckled top).


  • Give 15-20g oral glucose (90-120ml Lucozade, 3-4 teaspoons sugar in water, 150-200 ml fruit juice) if the patient is still conscious.
    • Check CBG in 15 min - if less than 4mmol/L, repeat above
    • Once CBG ≥4mmol/L, give long acting carbohydrate e.g. 1 slice of bread, 200ml milk or next meal if due
  • If the patient is unconscious or unable to swallow, treat with (with exceptions notes below) should be with 1mg Glucagon i.m
  • If Glucagon does not correct the low blood glucose within 10 - 15 minutes (and this includes prior administration by ambulance staff), give 200 ml of 10% glucose i.v. stat
  • Once CBG ≥4mmol/L, give long acting carbohydrate e.g. 1 slice of bread, 200ml milk or next meal if due
  • If the patient does not recover consciousness, check CBG and give further 200ml of 10% glucose


  1. Intravenous glucose, rather than Glucagon injections, should be used in sulphonylurea-induced hypoglycaemia and with hepatic disease. Sulphonylurea-induced hypoglycaemia may be very prolonged (several days)
  2. If Addison's disease or hypopituitarism is suspected, blood should be taken for later assay or cortisol and ACTH, and Hydrocortisone 200 mg i.v. as a bolus should be given prior to intravenous glucose
  3. In alcoholics parenteral thiamine (Pabrinex) should be given with the glucose (? Wernicke's)

Content by Dr Íomhar O' Sullivan 09/07/2002. Reviewed by Dr ÍOS 18/05/2005, 28/09/2006, 28/03/2007. 24/08/2008. Last review Dr IOS 15/06/21.