Hypoglycaemia, also called a hypo or low blood sugar, is an abnormally low level of glucose in the blood. NHS inform describes hypoglycaemia as a blood glucose level below 4 mmol/L.
It is most often discussed in relation to diabetes treatment, especially insulin and some tablets that increase insulin release. It can also occur in people without diabetes, but this is much less common and usually needs investigation for an underlying cause.
Symptoms
Symptoms vary, but common warning signs include:
- Hunger.
- Sweating.
- Trembling or shakiness.
- Dizziness.
- Tiredness.
- Blurred vision.
- Fast pulse or palpitations.
- Tingling lips.
- Irritability or anxiety.
- Difficulty concentrating.
- Confusion.
Severe hypoglycaemia can cause drowsiness, seizures, collapse, or loss of consciousness. Some people, especially those who have had diabetes for a long time, may lose their early warning symptoms. This is known as impaired awareness of hypoglycaemia.
Causes in Diabetes
In people with diabetes, hypoglycaemia is usually linked to the balance between medicine, food, exercise, and alcohol. Causes include:
- Taking too much insulin for the amount of carbohydrate eaten.
- Taking sulphonylurea or similar medication that increases insulin release.
- Missing or delaying a meal.
- Eating less carbohydrate than planned.
- Exercising more than expected.
- Drinking alcohol, especially without food.
- Changes in injection site absorption.
- Illness, weight change, or changes to routine.
The same glucose number may affect people differently, so diabetes teams often give individual advice on targets and prevention.
Causes Without Diabetes
Hypoglycaemia without diabetes is uncommon. Possible causes include prolonged fasting, malnutrition, heavy alcohol intake, severe liver or kidney disease, adrenal insufficiency, some medicines, previous gastric surgery, and rare insulin-producing tumours.
Because the cause may be unclear, repeated episodes in someone without diabetes should be assessed clinically.
Immediate Treatment
Mild hypoglycaemia is usually treated with fast-acting carbohydrate. NHS inform gives examples such as dextrose tablets, fruit juice, or a non-diet soft drink. A common adult treatment amount is about 15 to 20 g of rapidly acting carbohydrate, followed by rechecking glucose after about 15 minutes where testing is available.
After glucose has recovered, a longer-acting carbohydrate may be needed, especially if the next meal is not due. Examples include a sandwich, biscuits, fruit, or a cereal bar.
Chocolate is not usually the best first treatment because fat can slow sugar absorption.
Severe Hypoglycaemia
If a person is drowsy, fitting, or unconscious, food or drink should not be put in their mouth because of choking risk. A trained person may give glucagon if it is available and prescribed. Emergency help is needed if glucagon is not available, no trained person is present, or the person does not recover promptly.
Prevention
Prevention usually involves identifying patterns. Measures may include:
- Regular blood glucose monitoring where advised.
- Carrying rapid-acting carbohydrate.
- Eating regular meals or snacks when needed.
- Adjusting insulin or food around exercise.
- Taking care with alcohol.
- Reviewing medication after repeated hypos.
- Teaching family, friends, or carers what to do in an emergency.
People who have frequent hypos, severe hypos, night-time hypos, or loss of warning symptoms should discuss this with their diabetes team.
Driving
Hypoglycaemia can impair concentration, reaction time, and consciousness. In the UK, drivers with diabetes treated with insulin or some glucose-lowering medicines may have legal duties to monitor glucose and inform the DVLA in defined circumstances. NHS inform advises people at risk to test before driving, test during longer journeys, avoid driving when glucose is low, and avoid driving for a period after treating a hypo.
References
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