Broadly, there are 3 causes of hypoglycaemia in diabetic patients who take insulin.

  1. Too much exogenous insulin. This can be accidental or intentional.
  2. Too little food intake, such as due to vomiting.
  3. Increased metabolic demands such as occurs during strenuous/unaccustomed exercise or illness. Patients who have taken their normal insulin dose are not able to then modulate/reduce insulin levels during exertion as would normally happen in healthy individuals.