29th May 2025

Hypoglycaemia

In T2DM, hypoglycaemia is usually seen as a result of taking either insulin or sulfonylureas, although it can occur without these medications. It is defined as a blood glucose level <3.5mmol/L and can be classified by severity according to the symptoms experienced:

• Mild – hunger, anxiety, palpitations, sweating, perioral paraesthesia. 
• Moderate – headache, impaired cognition, reduced level of awareness, drowsiness and features of mild hypoglycaemia.
• Severe – seizures, loss of consciousness and coma.

Some patients will only experience symptoms at a very low blood glucose level, meaning they have impaired hypoglycaemia awareness (IHA). This is especially observed in patients who have had repeated episodes of hypoglycaemia and patients taking certain medications, including beta-adrenergic antagonists (e.g., bisoprolol), beta-adrenergic agonists (e.g. terbutaline), serotonin receptor reuptake inhibitors (e.g. serotonin) and methylxanthines (e.g. caffeine). Patients and, where appropriate, relatives and carers should be educated about the symptoms of hypoglycaemia and advised on emergency management. This is especially important in patients with known IHA as they are more liable to progress to severe hypoglycaemia and will therefore be unable to administer emergency treatment.

The management of hypoglycaemia involves increasing the circulating glucose level as quickly as possible and there are several ways this can be achieved:

• Oral fast-acting carbohydrate – Conscious patients, who can swallow, with blood glucose <4mmol/L with or without symptoms of hypoglycaemia should be given a fast-acting oral carbohydrate such as 40% glucose gel, glucose tablets or glucose liquid. In the community, if these agents are unavailable, then any accessible sugary foods should be used, such as orange juice or candies. The treatment may be repeated up to 3 times at 15-minute intervals if there is not a satisfactory response. 
• IM Glucagon – If there is no response to oral agents and the patient doesn’t have intravenous access then they should be given glucagon via intramuscular injection. Glucagon should also be given to unconscious patients and can be administered by appropriately trained family members. Glucagon doesn’t increase the total amount of glucose in the body, rather mobilising stored glucose in the liver, and therefore will be ineffective in patients that have depleted glucose stores. It should therefore be avoided in patients who have undergone a prolonged fast, have adrenal insufficiency or have alcohol-induced hypoglycaemia. It is also less effective in patients who take a sulfonylurea. 
• IV Glucose infusion – Patients who have not responded to oral agents and have intravenous access should be started on either a 10% or 20% glucose infusion. 50% glucose should be avoided as it is a hypertonic solution.  Patients who are unconscious and haven’t responded to or aren’t suitable for IM glucagon should also be treated with IV glucose. Alcoholic patients should be co-administered IV thiamine to reduce the risk of Wernicke’s encephalopathy (thiamine plays an important role in the intracellular metabolism of glucose). 

Once blood glucose >4mmol/L the patient should be given a source of long-acting carbohydrate (such as a slice of toast, 2 biscuits or a glass of milk) if able to eat. Patients who are NBM should be started on a 10% insulin infusion. In T2DM, since most hypoglycemia is seen in response to a sulfonylurea or insulin, the hypoglycaemia can persist for up to 36 hours so blood glucose should be monitored closely.