Last updated: 04 October 2011
Hypoglycaemia means an abnormally low level of sugar (glucose) in the blood - usually under 4 millimoles per litre.
When your glucose level is too low - called a 'hypo' - your body does not have enough energy to carry out its activities.
Most people will have some warning that their blood glucose levels are too low, giving them time to correct it. Typical early warning signs are feeling hungry, trembling or shakiness and sweating (see Symptoms).
How it is corrected
The immediate treatment for a hypo is to have some food or drink containing sugar (such as chocolate, sugar cubes or fruit juice) straight away to end the attack.
After having something sugary, it may be necessary for you to have a longer-acting carbohydrate food such as a few biscuits or a sandwich, depending on which insulin you are using (see Treatment).
If hypoglycaemia is not treated, it may lead to unconsciousness, because there is not enough glucose for normal brain function.
At this stage, an injection of the hormone glucagon can be given to quickly raise blood glucose levels and restore consciousness.
Who is affected
Hypoglycaemia occurs mainly in people with diabetes (usually type 1 diabetes) who have taken too much diabetes medication, missed a meal, or drunk alcohol on an empty stomach. For more information, see Causes.
People with type 2 diabetes who manage their blood glucose levels without medication will generally not have a hypo.
Preventing an attack
The safest way of avoiding a hypoglycaemic attack is to keep a regular check on your blood sugar and know how to recognise the early symptoms. Make sure you eat regularly and do not miss meals (see Prevention).
You should always carry with you dextrose tablets, a carton of fruit juice or a chocolate bar in case you feel symptoms coming on or you detect a low level on your glucose-testing meter.
Continue to next section: Symptoms of hypoglycaemia