Hypoglycaemia (Low Blood Sugar) – Causes, Signs and Treatment

The opposite of having high blood sugar (hyperglycaemia) is having low blood sugar, known as hypoglycaemia. Like hyperglycaemia, it most commonly affects people with diabetes, but it can occur in anyone under certain conditions.

What Is Hypoglycaemia?

Hypoglycaemia occurs when a person’s blood glucose level falls below 4 millimoles per litre (mmol/L). It is more common in people with diabetes who are treated with insulin, but it may also develop due to:

• Prolonged fasting or skipping meals.
• Excessive alcohol consumption.
• Critical illness or severe underlying medical conditions.

As with hyperglycaemia, untreated hypoglycaemia can be very dangerous. If not managed quickly, it can lead to seizures, coma or even death. The good news is that mild to moderate episodes are usually quick and simple to treat if recognised early.

Signs and Symptoms of Hypoglycaemia

Hypoglycaemia typically has a very rapid onset, which can help distinguish it from hyperglycaemia, where symptoms usually develop more slowly.

Common signs and symptoms of low blood sugar include:

• Noticeable changes in behaviour, such as irritability, confusion or unusual agitation.
• Hunger or a sudden strong desire to eat.
• Cold, sweaty or clammy skin.
• Rapid pulse but a normal breathing rate.

Any combination of these symptoms, especially with a known history of diabetes, should raise suspicion of hypoglycaemia.

Immediate First Aid for Hypoglycaemia

While severe cases of hypoglycaemia may require emergency medical help, many mild to moderate episodes can be treated quickly and effectively.

For Adults and Older Children

People who are prone to hypoglycaemia, such as those with diabetes, are usually advised to carry a quick source of sugar with them at all times. This may include:

• Glucose gels.
• Glucose tablets.
• A quick-release high-sugar snack, such as a chocolate bar or a sugary drink.

If symptoms of hypoglycaemia are present and the person is conscious and able to swallow safely:

1. Give them a rapid-acting sugary food or drink as soon as possible.
2. Wait around 10–15 minutes, then re-test their blood glucose level if they have a meter available.
3. If their level is still low, repeat a quick source of sugar and monitor closely.

If the person’s condition does not improve, if they become drowsy, confused, or lose consciousness, call the emergency services immediately.

For Young Children

In young children, if hypoglycaemia is suspected and they are conscious and able to swallow, you may give around half a teaspoon (about 2.5 grams) of sugar, for example:

• Placed carefully under the tongue, or
• Dissolved in a small amount of water if easier for the child to manage.

Continue to observe the child closely and seek medical advice if there is no improvement or symptoms worsen.

When to Call for Emergency Help

You should call emergency medical services (999 in the UK) if:

• The person becomes unconscious or is difficult to rouse.
• They have a seizure.
• They are unable to swallow safely or keep food or drink down.
• There is no improvement after giving quick-acting sugar and waiting 10–15 minutes.

Hypoglycaemia can be life-threatening if ignored, but with early recognition and prompt treatment, most episodes can be managed safely and effectively.