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What Is Hypoglycaemia?

In people without diabetes the level of glucose in the blood is controlled by insulin produced be the beta cells in the pancreas. This prevents the level of glucose in the blood from rising too high. In people with Type 1 diabetes, the body does not produce its own insulin and the blood glucose levels rise too high [hyperglycaemia] and so injections of insulin are given to prevent this. People with diabetes are advised to keep their blood glucose levels as near to the normal blood glucose levels as possible. If the blood glucose levels drop below normal, whatever the cause, then this is called hypoglycaemia [a hypo]. ‘Good’ control of diabetes is avoidance of both high and low blood glucose levels.

Normal blood glucose levels in non-diabetic people range between 4 and 7mmols/l. Hypoglycaemia is usually said to occur at 3.8mmols/l and so the recommended lower level is 4mmols/l – hence the recommendation to people with diabetes that “4 is the Floor”.

Note: Some publications say that hypoglycaemia does not occur until blood glucose levels are below 3.5 or even 3.0mmols/l. However, there is research that shows that the ability to function may be impaired by blood glucose levels of 3.8mmols/l and lower.

Useful definitions of hypoglycaemia
It is important that even mild hypos, or ‘lows’, are recognised as being hypoglycaemia and treated. This is also important so that all hypos can be reported to your doctor to provide a true picture of your diabetic control.

Hypos are generally defined as follows:

Mild: a hypo that is easily treated by the patient by the intake of a sugary drink or food, often referred to as ‘being low’.

Moderate: one where someone else, spouse, friend or parent, has to intervene and give the sugary food/drink because the person with diabetes is confused or even losing consciousness

Severe: one that usually means unconsciousness which may be accompanied by a convulsion/seizure.

Parent comment: ‘I am sure that I under-reported my daughter’s hypos at our clinic visits because I was never sure how to answer the question about how many hypos she had since the last visit. I didn’t know whether to class the lows before meals as a hypo or not.’


For more information on hypoglycaemia, please visit the NHS Choices website:

NHS Choices: Hypoglycaemia