Causes of hypoglycaemia 

In most cases hypoglycaemia occurs in people with diabetes, although in rarer cases it can occur because of other underlying conditions.

Hypoglycaemia in people with diabetes

Overdose of diabetes medication

A common cause of hypoglycaemia is taking too much insulin for your current needs. Insulin is a medication that helps control your blood glucose levels. It is commonly used to treat type 1 diabetes, but it's also recommended for some people with type 2 diabetes.

A drop in blood glucose levels can also happen when you take too much oral hypoglycaemia medication such as sulphonylurea, which causes a release of insulin. This medication is often used to lower blood glucose levels in people with type 2 diabetes.

Exercise, food and alcohol

For people with type 1 diabetes, maintaining the correct blood glucose level involves balancing the amount of insulin you inject, the amount of food you eat and the amount of energy you burn during exercise.

Hypoglycaemia may occur if you have taken your dose of insulin as usual but your carbohydrate intake is lower than normal or has been used up more quickly. This may happen if you delay or miss a meal or snack, do not eat enough carbohydrate or do more exercise than usual.

Hypoglycaemia may also occur in people with diabetes who have drunk too much alcohol or who have drunk alcohol on an empty stomach.

However, it is not always possible to identify why a particular episode of hypoglycaemia has occurred as sometimes it happens in people with diabetes for no obvious reason.

Hypoglycaemia in people without diabetes

Hypoglycaemia (even mild cases) is very rare in people who don't have diabetes. The possible causes of hypoglycaemia in people without diabetes are outlined below.

Reactive hypoglycaemia

People without diabetes can sometimes experience hypoglycaemia if their pancreas produces too much insulin after a large carbohydrate-based meal. This is known as reactive hypoglycaemia. It is not clear why this happens, although it is thought to be more common in people who are overweight or have had gastric bypass surgery.

In rare cases, a benign (non-cancerous) tumour in the pancreas may cause an overproduction of insulin, or the tumour itself may use up too much glucose.

Other causes

Other possible causes of hypoglycaemia in people without diabetes are:

  • fasting or malnutrition – where you are not consuming enough nutrients for your body to function properly
  • binge drinking or heavy drinking of alcohol
  • Addison's disease – a disorder of the adrenal glands
  • certain medication – hypoglycaemia has been known to occur in people taking quinine (for malaria), salicylates (for rheumatic disease) and propranolol (for high blood pressure)
  • severe illnesses affecting the liver, kidneys or thyroid gland

Page last reviewed: 16/07/2013

Next review due: 16/07/2015