Hypoglycaemia

Hypoglycaemia refers to any episode of low blood glucose (usually <3.5 mmol/l) with or without symptoms and may occur in patients taking insulin, sulphonylureas or prandial glucose regulators. Mild episodes may not only be inconvenient for the patient, but may predispose to more severe episodes which are associated with significant morbidity as well as the development of fear of hypoglycaemia. Even if untreated, most isolated episodes recover spontaneously and are not associated with permanent damage. It is reasonable to reassure patients accordingly. Many patients will avoid strict blood glucose control in order to minimise their risk of experiencing hypoglycaemia.

Patients should be advised about how to avoid, recognise, and treat hypoglycaemia.

This should then be slip into sections:

Causes of hypoglycaemia

Symptoms of hypoglycaemia

Hypoglycaemia unawareness

Treatment of hypoglycaemia

Hypoglycaemia and sulphonylureas

Nocturnal hypoglycaemia

Rebound Hyperglycaemia

Driving and hypoglycaemia – See Section 9 and Appendix 4

Avoidance of hypoglycaemia

Causes of hypoglycaemia

Hypoglycaemiaoccurs when there is an imbalance between:

  • Carbohydrate intake
  • Insulin or oral hypoglycaemic drug dose
  • Exercise/activity.

Additional factors which may contribute to the risk of hypoglycaemia include lumpy injection sites (leading to erratic absorption of insulin), errors in insulin administration, alcohol excess (particularly if combined with reduced carbohydrate intake), gastroparesis in patients with autonomic neuropathy and adrenal insufficiency (particularly in patients with Type 1 diabetes).

Symptoms of hypoglycaemia

The symptoms of hypoglycaemia vary between patients and the same patient may experience different symptoms in different circumstances. Symptoms are classified as:

  • autonomic, due to activation of the autonomic nervous system (sweating, tremor, anxiety, palpitations etc)
  • neuroglycopenic due toreduced glucose delivery to the brain (poor concentration, odd behaviour, dizziness)
  • non-specific (headache, tingling lips etc)

In most patients the autonomic symptoms occur before the neuroglycopenic symptoms and provide a useful warning. Patients with poor control and chronic hyperglycaemia may experience symptoms of hypoglycaemia at higher blood glucose levels. This is an indication for more gradual step-wise improvement in blood glucose control.

Hypoglycaemia unawareness

In some patients the order of onset of symptoms may be reversed e.g. those with long-duration of diabetes, very tight glycaemic control or recurrent episodes of hypoglycaemia or during pregnancy. This may result in hypoglycaemia unawareness when the patient is unable to recognise the onset of the hypo, which can have serious consequences. In some people it may be possible to regain the normal symptoms of hypoglycaemia through meticulous avoidance of hypoglycaemia and specialist advice may be required. A three or four months period of relaxation of glycaemic control may be appropriate, i.e. minimum blood sugar of 6 mmol/l.

Treatment of hypoglycaemia

All patients treated with insulin or sulphonylureas or prandial glucose regulators should be advised to carry carbohydrate with them. As soon as symptoms are recognised or if a low blood glucose value is recorded (with or without symptoms), the patient should be advised to take one of the following:

  • 3 Dextrosol tablets or sugar lumps
  • Half of a small bottle (150ml) of lucozade or equivalent sugary drink e.g. cola – (not diet or lite)
  • Fruit juice – 1 glass
  • Chocolate e.g. Mini Mars bar

If the patient is taking acarbose glucose e.g. Dextrosol must be used for treatment of hypoglycaemia (not a disaccharide such as sucrose (sugar) or lactose (milk)).

If symptoms are not improving after 10 minutes this should be repeated. If the patient is too drowsy to co-operate, “Hypostop”, honey or jam may be applied to the inside of the cheeks and massaged from the outside. It may be advisable for patients to keep Hypostop at home and to instruct family members and friends how to use it.

If the patient is unresponsive, 1 mg of glucagon should be given subcutaneously or intramuscularly (once only per episode). It may be advisable to instruct partners, close relatives or friends of insulin-treated people in the use of glucagon and to ensure that they keep a kit at home.

Alternatively 25g (50ml 50%) of dextrose can be given intravenously by professional help.

After the initial treatment it is essential for the patient to take long acting carbohydrate such as biscuits and milk, or a sandwich to prevent the hypoglycaemia from recurring.

Hypoglycaemia and sulphonylureas

Hypoglycaemia may occur in patients taking sulphonylureas and is often underreported in the elderly when the symptoms are non-specific and are confused with other conditions e.g. TIA’s. Hypoglycaemia may recur following initial treatment and sometimes admission to hospital may be required. The earlier generation of long-acting sulphonylureas (chlorpropamide and glibenclamide) should not be initiated and are probably best avoided in those over 65. However the newer type of long-acting sulphonylurea, e.g. Glimepiride and modified release Gliclazide do not appear to be associated with an increased risk of hypoglycaemia.

Nocturnal hypoglycaemia

This is a common occurrence in insulin-treated patients. Patients may or may not wake up during the night with symptoms, or sometimes wake up the following morning feeling “hung-over”. Nocturnal hypoglycaemia may contribute to the development of hypoglycaemia unawareness. The risk can be minimised by ensuring a snack containing complex carbohydrate is taken at bedtime (irrespective of blood glucose reading), and allowing the blood glucose to be between 7 and 9 at bedtime. The following measures may reduce the risk of nocturnal hypoglycaemia:

  • Splitting the evening insulin dose so that the quick acting insulin is taken before the evening meal and the intermediate acting insulin is taken at bedtime
  • Replacing soluble insulin at teatime with a shorter acting insulin analogue e.g. Lispro
  • Insulin glargine (Lantus) appears to be associated with a lower incidence of hypoglycaemia in patients on a basal bolus regime.

Rebound Hyperglycaemia

After an episode of hypoglycaemia patients may experience marked hyperglycaemia, which may be prolonged, as a result of the release of conterregulatory hormones. It must therefore be remembered that hyperglycaemia may indicate an earlier period of hypoglycaemia. This is often pertinent after an unrecognised hypoglycaemic event, particularly at night.

Driving and hypoglycaemia – See Section 9 and Appendix 4

Patients should be advised to check their blood glucose before and during long car journeys and should always carry carbohydrate in the car. If they have a hypo while driving they should stop the car, remove the keys from the ignition, leave the driver’s seat and take oral carbohydrate. Driving should not be resumed for at least 45 minutes. Patients who have lost their warning symptoms of hypoglycaemia should be advised not to drive until the problem has been resolved. This advice should be documented in clinical records.

Avoidance of hypoglycaemia

The risk of severe hypoglycaemia can be minimised by self-monitoring of blood glucose, review of insulin / drug regimen, quantity and timing of carbohydrate intake and injection sites. Patients should be advised to “Keep 4 the floor” with respect to their targets for glucose control. However in some patients who do not monitor or who have had problems with severe hypoglycaemia the targets for glycaemic control may need to be relaxed.