Causes of hypoglycaemia 

In most cases, hypoglycaemia affects people with diabetes, although more rarely it can also occur as a result 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's commonly used to treat type 1 diabetes and is also recommended for some people with type 2 diabetes.

A fall in blood glucose levels can also occur after taking 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 how much insulin you inject, the amount of food you eat, and how much energy you burn during exercise.

Hypoglycaemia may occur if you've 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, don't eat enough carbohydrate, or exercise more than usual.

People with diabetes who've drunk too much alcohol, or drank alcohol on an empty stomach, can also get hypoglycaemia.

However, it's not always possible to identify why a particular episode of hypoglycaemia has occurred, and sometimes it happens 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 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's not clear why this happens, although it's 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 possible causes

Other possible causes of hypoglycaemia in people without diabetes are:

  • fasting or malnutrition – where not enough nutrients are consumed for your body to function properly
  • binge drinking or heavy drinking of alcohol
  • Addison's disease – a disorder of the adrenal glands (two small glands that sit on top of the kidneys) 
  • 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: 21/05/2015

Next review due: 21/05/2017