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Hypoglycaemia (low blood sugar) in diabetes
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Reviewed by Professor Ian W Campbell, consultant physician
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Did you know?
The
blood sugar level is
the amount of glucose in the blood. It is expressed as millimoles per litre (mmol/l).
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Hypoglycaemia is a condition where the level of glucose (sugar)
in the blood drops below a certain point – about 3.0mmol/l.
This causes a number of symptoms such as dizziness, sweating,
shaking and palpitations, that usually go away 10 to 15 minutes after eating
sugar.
What causes hypoglycaemia?
Insulin is normally produced in the pancreas and helps the
body's cells absorb glucose from the blood:
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After a meal the glucose level rises after a meal to about
7-10mmol/l.
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One to two hours later, the glucose level starts dropping
again. By the next meal, the glucose level is back to normal: about 4-5mmol/l.
The insulin level in the blood has also returned to normal.
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Term watch
A 'hypo' is the short name given to episodes
of low blood sugar.
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Hypoglycaemic episodes (hypos) can be caused by:
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over-treatment - the dose of insulin or
diabetes tablets is set too high or you accidentally take too much.
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mismatched calorie intake versus demand - this
happens when your body needs energy but can't get it from your calorie intake
ie if you eat less than usual or exercise more.
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alcohol - alcoholic drinks tend to lower the
blood sugar.
What happens during a hypo?
You can experience some or all of the following
symptoms:
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Did you know?
Hypoglycaemic episodes are categorised as:
mild – you can manage these episodes alone.
serious – you'll need help from others, such
as a family member or doctor.
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paleness
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shaking
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perspiration
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a feeling of weakness
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rapid heartbeat
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hunger
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agitation
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difficulty concentrating
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irritability
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fatigue
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blurred vision
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temporary loss of consciousness
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confusion
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convulsions
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coma.
Most people do get some warning that hypoglycaemia is
happening.
But for some, hypoglycaemia may cause few or none of the warning
symptoms before the start of sudden unconsciousness or convulsions –
particularly if you've had diabetes for many years.
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Caution
The aim of diabetes treatment is to have as near normal levels
of blood sugar as possible.
Deliberately running higher glucose levels should only be done
on a doctor’s advice.
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This means loss of consciousness can occur without warning.
To avoid this, you are advised to:
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maintain a higher level of glucose in the blood
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measure your blood sugar level more frequently.
How is a diagnosis made?
Diagnosis is made by
measuring the blood sugar
level with a glucose meter.
A glucose level below 3.0mmol/l indicates
hypoglycaemia.
Some people experience symptoms when their blood sugar level is
higher than this – eg at 4.0mmol/l. (Therefore 'four is the floor' for blood
glucose levels.)
Hypos can't be detected with urine tests for glucose.
How is hypoglycaemia treated?
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Did you know?
If you use insulin, your blood sugar level is:
highest 1-2 hours after a meal
lowest 3-4 hours after a meal.
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Mild hypoglycaemia is treated by drinking or eating about
10-20g sugar, eg in the form of sweetened juice, milk or glucose tablets.
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In the case of a more serious hypo, an ambulance should be
called. The paramedic will then give glucose intravenously or
glucagon
(GlucaGen) (a glucose-increasing hormone) is injected into a muscle, or
into the fatty tissue under the skin.
Your partner and other family members can also be taught to
give glucagon injections at home.
A glucagon kit can then be provided so if you suffer several
hypos with unconsciousness, immediate treatment is available. In this way, a
hospital visit can be avoided.
If you experience hypos repeatedly, you should measure blood
sugar level at least four times a day. This allows you to adjust your insulin
and know when you need a snack.
What can I do about hypoglycaemia?
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Be familiar with the warning symptoms of
hypoglycaemia. This way, you can get treatment quickly. When in doubt,
measure your blood sugar levels.
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Always carry sugar – preferably glucose in a
rapidly-absorbed form such as glucose tablets.
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Measure glucose levels regularly. How often
depends on your lifestyle – it's something that a combination of practical
experience and expert advice will determine. It can vary from one or two
readings a week to several readings a day. Knowing how your blood sugar levels
change with various activities means you can adjust your level of insulin and
minimise the risk of a hypo.
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Follow the dietician’s advice and maintain regular
eating habits. Some people experience symptoms of a hypo just before a
main meal. To avoid this, have snacks between meals to prevent sugar levels
dropping too steeply.
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Take care when exercising: exercise lowers
glucose levels in the blood. You can counter this by taking less insulin than
usual beforehand or by eating more before, during or just after exercise.
Remember that hypoglycaemia may occur some hours after exercise.
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Carry an identity card that lets others know
you have diabetes.
At night
For many people with diabetes, a low blood sugar level during
the night is a big problem because you can sleep through it.
If you wake up with a
headache and feel
unusually irritable, measure your blood sugar at about 3am.
Lower your risk of a hypo by measuring blood sugar at 10pm or
11pm. If it's below 8mmol/l, eat a snack.
Alcohol lowers the blood sugar just like insulin – so avoid
alcoholic binges.
After drinking a lot of alcohol or dancing, eat a snack before
going to bed.
In the long term
Normally, hypoglycaemia is easily treatable. A few mild episodes
in a week are not harmful.
It starts to become dangerous only when the glucose level keeps
dropping below acceptable limits – the brain's principal source of energy is
glucose.
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Based on a text by Dr Jan Erik Henriksen and Professor Henning Beck-Nielsen
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Last updated 22.09.2008
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