Hypoglycaemia (low blood sugar)

Causes of hypoglycaemia

In most cases, hypoglycaemia affects people with diabetes, although more rarely it can also occur as a result of other underlying conditions.

Hypoglycaemia in people with diabetes

Overdose of diabetes medication

A common cause of hypoglycaemia is taking too much insulin for your current needs. Insulin is a medication that helps control your blood glucose levels. It’s commonly used to treat type 1 diabetes and is also recommended for some people with type 2 diabetes.

A fall in blood glucose levels can also occur after taking too much oral hypoglycaemia medication, such as sulphonylurea, which causes a release of insulin. This medication is often used to lower blood glucose levels in people with type 2 diabetes.

Exercise, food and alcohol

For people with type 1 diabetes, maintaining the correct blood glucose level involves balancing how much insulin you inject, the amount of food you eat, and how much energy you burn during exercise.

Hypoglycaemia may occur if you’ve taken your dose of insulin as usual, but your carbohydrate intake is lower than normal or has been used up more quickly. This may happen if you delay or miss a meal or snack, don’t eat enough carbohydrate, or exercise more than usual.

People with diabetes who’ve drunk too much alcohol, or drank alcohol on an empty stomach, can also get hypoglycaemia.

However, it’s not always possible to identify why a particular episode of hypoglycaemia has occurred, and sometimes it happens for no obvious reason.

Hypoglycaemia in people without diabetes

Hypoglycaemia – even mild cases – is very rare in people who don’t have diabetes. The possible causes are outlined below.

Reactive hypoglycaemia

People without diabetes can sometimes experience hypoglycaemia if their pancreas produces too much insulin after a large carbohydrate-based meal. This is known as reactive hypoglycaemia.

It’s not clear why this happens, although it’s thought to be more common in people who are overweight or have had gastric bypass surgery.

In rare cases, a benign (non-cancerous) tumour in the pancreas may cause an overproduction of insulin, or the tumour itself may use up too much glucose.

Other possible causes

Other possible causes of hypoglycaemia in people without diabetes are:

• fasting or malnutrition – where not enough nutrients are consumed for your body to function properly
• binge drinking or heavy drinking of alcohol
• Addison’s disease – a disorder of the adrenal glands (two small glands that sit on top of the kidneys)
• certain medication – hypoglycaemia has been known to occur in people taking quinine (for malaria), salicylates (for rheumatic disease) and propranolol (for high blood pressure)
• severe illnesses affecting the liver, kidneys or thyroid gland

Treating hypoglycaemia

In most cases, you can treat hypoglycaemia yourself when you recognise the symptoms.

Treating an episode of hypoglycaemia

The immediate treatment for hypoglycaemia is to have some sugary food or drink (about 15 to 20g of rapidly acting carbohydrate) to end the attack.

For example, this could be:

• a glass of fruit juice or non-diet soft drink
• between three and five dextrose tablets
• a handful of sweets

At first you should avoid fatty foods and drinks, such as chocolate and milk, because they don’t usually contain as much sugar and the sugar they do contain may be absorbed more slowly.

After having something sugary, you should have a longer-acting carbohydrate food, such as a few biscuits, a cereal bar, a piece of fruit or a sandwich.

It will usually take around 15 minutes to recover from a mild episode of hypoglycaemia. If you have a blood glucose meter, measure your blood sugar again after 15 to 20 minutes. If it’s still too low (below 4mmol), you should have some more sugary food or a drink before testing your levels again in another 15 to 20 minutes.

When treating someone else with hypoglycaemia, if the above treatment isn’t effective, you may be able to help them by applying glucose gel (or honey, treacle or jam if glucose gel isn’t available) to the inside of their cheeks, and gently massaging the outside of their cheeks.

It may take 10 to 15 minutes before they feel better. This shouldn’t be done if the person is drowsy or unconscious because of the risk of choking.

If you have several episodes of hypoglycaemia a week, you should contact your diabetes care team to find out the underlying cause. Your medication may need to be adjusted, or there may be another condition causing hypoglycaemia that needs to be treated.

If a person is unconscious

If a person loses consciousness because of severe hypoglycaemia, they need to be put into the recovery position and given an injection of the hormone glucagon (if they have an injection kit). The injection will raise their blood glucose level.

The injection should be carried out by a friend or family member who knows what they’re doing, or by a trained healthcare professional.

You should dial 999 to request an ambulance if:

• a glucagon injection kit isn’t available
• there’s nobody available who’s trained to give the injection
• the injection is ineffective after 10 minutes

Never try to put food or drink into the mouth of someone who’s unconscious as they could choke.

If you’re able to give a glucagon injection and the person regains consciousness, they should eat some longer-acting carbohydrate food, such as a few biscuits, a cereal bar or a sandwich.

You should continue to monitor the person for signs of recurring symptoms in case they need to be treated again.

Monitoring blood glucose

Regularly monitoring your blood glucose levels can help you keep your blood glucose as normal and stable as possible, and will help you spot the signs and symptoms of hypoglycaemia quickly.

Your blood glucose level can vary throughout the day, so you may need to check it several times a day, depending on the treatment you’re taking.

You can monitor your blood glucose levels using a blood glucose meter, a small device that measures the concentration of glucose in your blood.

Read more about living with type 1 diabetes and living with type 2 diabetes

Food and alcohol

If you have diabetes, strenuous physical activity can lead to hypoglycaemia. Eating extra carbohydrate-based foods before and during exercise can help reduce the chances of this happening.

If you’re taking insulin, your doctor may advise you to lower your dose before you do strenuous physical activity.

Alcohol can also affect your body’s ability to release glucose. If you have type 1 diabetes, it’s recommended that you drink no more than 2 to 3 units of alcohol a day and eat a snack after drinking alcohol.

Spotting the signs

As hypoglycaemia can develop suddenly, it’s important to be aware of the symptoms of hypoglycaemia so you can treat it quickly. Tell your family and friends about the signs to look out for and let them know how to treat it.

People with diabetes are advised to carry a form of identification with them that states their condition so they can be helped quickly and efficiently.

Keep treatment with you

If you’re at risk of hypoglycaemia, you should carry sugary food and drink with you at all times to treat mild cases as soon as possible.

If you have diabetes, particularly type 1 diabetes, your doctor may recommend medications such as glucose gel to carry with you. This can be used to treat hypoglycaemia that doesn’t respond to normal treatment.

If you’re being treated with insulin, you’ll usually be given a kit that contains an injection of a medication called glucagon. Family members or your carer can be trained to carry out the injection, which should be used if you lose consciousness because of severe hypoglycaemia.

If you have diabetes and treat it with insulin, the safest way to avoid hypoglycaemia is to check your blood sugar regularly and learn to recognise the early symptoms.

Missing meals or snacks, or eating less carbohydrate than planned, can raise your risk of hypoglycaemia. Be careful with alcohol too, since it can also cause hypoglycaemia, sometimes many hours after you have had a drink.

Exercise or physical activity is another possible trigger, so it helps to have a plan in place, such as eating some carbohydrate before, during, or after exercise, or adjusting your insulin dose.

You should also change where you inject insulin on a regular basis, since the amount of insulin your body absorbs can vary depending on the injection site.

Always keep some fast acting carbohydrate with you, such as glucose tablets, a carton of fruit juice that contains sugar, or some sweets, in case you feel symptoms starting or your blood glucose level is low.

Make sure your friends and family understand your diabetes and the risk of hypoglycaemia. It can also help to carry some form of identification that tells people about your condition in an emergency.

When hypoglycaemia happens because of an underlying condition other than diabetes, that condition needs to be treated to prevent further episodes.

If you have diabetes, sticking to your medication plan and eating regular meals can help prevent hypoglycaemia. Monitoring your blood glucose levels regularly is important too.

Hypoglycaemia while sleeping

Having a hypo while you are asleep is called nocturnal hypoglycaemia. It is more common in people who treat diabetes with insulin.

Some people find their sleep is disturbed when this happens, but others only notice the symptoms after they wake up in the morning.

Symptoms of nocturnal hypoglycaemia can include:

• a headache, often described as feeling like a hangover
• feeling unusually tired in the morning
• damp sheets or clothing from sweating during the night

Preventing hypoglycaemia at night

It is important to avoid repeated hypoglycaemia during the night, since it can dull the early warning symptoms of episodes during the day. If you experience nocturnal hypoglycaemia, you could try:

• keeping something sugary by your bedside
• having a snack before bed, such as biscuits and milk
• checking your blood glucose level between 3am and 4am, since this is when hypoglycaemia is most likely to occur

Hypoglycaemia and driving

Because hypoglycaemia can cause confusion, drowsiness, or even loss of consciousness, it can pose a serious risk to you and to other road users.

If you have diabetes that requires insulin treatment, you must:

• inform the relevant licensing authority (such as the DVLA in the UK, or the equivalent body where you live) and your insurance company
• check your blood sugar before driving, and again at regular intervals, at least every two hours, while driving
• avoid driving if your blood glucose is low
• avoid driving for 45 minutes after treating hypoglycaemia
• keep fast acting carbohydrates in the vehicle with you at all times

If hypoglycaemia occurs while you are driving, pull over and stop as soon as it is safe to do so. Take the keys out of the ignition and get out of the driver's seat before treating the hypoglycaemia in the usual way.

If you have two or more episodes of hypoglycaemia that require someone else's assistance within a 12 month period, you are legally required to stop driving and inform the DVLA or your local equivalent.

If you hold a licence for buses, coaches, or lorries (a group two licence in the UK system), you are legally required to stop driving these vehicles immediately and inform the licensing authority after even a single episode of hypoglycaemia that requires assistance.

Let your diabetes care team know if you start finding it harder to recognise hypoglycaemia, or if episodes become more frequent, even if you had warning symptoms and managed to treat them yourself without help.