Hypoglycaemia (Low Blood Sugar)

Overview

Hypoglycaemia (low blood sugar) happens when the level of glucose (sugar) in your blood drops too low to give your body enough energy. Glucose is your body's main fuel, and without enough, your brain and muscles can't work properly.

Yes, hypoglycaemia is very common, especially among people with diabetes. Many people with diabetes experience mild low blood sugar at some point, and some have it often.

Hypoglycaemia mostly affects people with diabetes, especially those on insulin or medications that help the body make more insulin. It can also happen in people without diabetes, but this is much less common.

Symptoms

Common symptoms

• Shakiness or trembling
• Sweating
• Feeling hungry
• Fast heartbeat
• Dizziness or light-headedness
• Blurred vision
• Mood changes, such as irritability or anxiety
• Tingling lips or tongue

Symptoms in children

• Crying or fussiness
• Pale skin
• Tiredness or sleepiness
• Coordination problems or clumsiness
• Nightmares or crying out during sleep

Symptoms in older adults

• Confusion or disorientation
• Slurred speech
• Weakness or dizziness that may increase fall risk
• Unusual behaviour or irritability
• Difficulty concentrating

Causes

Main causes

• Taking too much insulin or diabetes medication
• Skipping or delaying a meal
• Eating less than usual without adjusting medication
• Exercising more than usual without extra food
• Drinking alcohol, especially on an empty stomach

Risk factors

• Having diabetes, especially type 1 diabetes
• Using insulin or medications that increase insulin production (like sulfonylureas)
• Having kidney or liver disease
• Being very young or very old
• Having had a previous severe low blood sugar episode

When to see a doctor

See a doctor urgently if:

• If you have a severe episode that requires help from others (like glucagon or emergency services)
• If you have repeated episodes without a clear cause
• If you experience loss of consciousness or seizure

Book a routine appointment if:

• If you have mild low blood sugar more than once a week
• If you cannot seem to prevent episodes despite following your usual treatment plan
• If you need help adjusting your diabetes medications or insulin

Diagnosis

Hypoglycaemia is diagnosed when your blood sugar level is below 3.9 mmol/L (70 mg/dL) and you have symptoms that get better when you eat something sugary. Doctors may also check your blood sugar during symptoms to confirm.

Tests that may be done

• Blood glucose test (finger-prick or lab test)
• Continuous glucose monitoring (CGM) to track trends
• Oral glucose tolerance test (in some cases to check for reactive hypoglycaemia)

What to expect at your appointment

Your doctor will ask about your symptoms, when they happen, and what you eat and do. They may ask you to check your blood sugar at specific times. If you do not have diabetes, they may run additional tests to look for other causes, such as a rare tumour (insulinoma) or hormone problems.

Treatment

Treatment for hypoglycaemia is usually simple: raise your blood sugar quickly with fast-acting sugar, then eat a longer-lasting snack to prevent it from dropping again. The key is to act quickly at the first sign of symptoms.

Self-care at home

• Eat or drink about 15 grams of fast-acting sugar (such as fruit juice, regular soda, glucose tablets, or a small handful of sweets).
• Wait 15 minutes and check your blood sugar again. If it is still low, repeat the sugar.
• Once your blood sugar is back to normal, eat a meal or snack that contains longer-acting carbohydrates (like a sandwich or fruit with yoghurt).
• If you have diabetes, always carry a source of fast-acting sugar with you.
• If you are at risk of severe episodes, make sure your family and friends know how to help.

Medical treatments

For severe hypoglycaemia where you cannot swallow or are unconscious, a trained person can give an injection of glucagon (a hormone that raises blood sugar) or a nasal powder. Your healthcare provider can prescribe this and teach you and your family how to use it. In a hospital, doctors may give glucose intravenously (through a vein) if needed.

When is surgery considered?

Surgery is very rarely needed for hypoglycaemia. It may be considered if a benign insulin-producing tumour (insulinoma) is found, but this is extremely uncommon.

Living with this condition

Living with hypoglycaemia means staying aware of your blood sugar levels and knowing what to do when it drops. Many people learn to recognise their early warning signs and treat them quickly. It can be stressful, but with a good plan, most people manage well.

Lifestyle tips

• Eat regular meals and snacks, especially if you take insulin or certain diabetes medications.
• Carry a source of fast-acting sugar with you at all times (like glucose tablets or a small box of raisins).
• Wear a medical ID bracelet or necklace if you have diabetes and are at risk of low blood sugar.
• Tell your friends, family, and colleagues how to help you if your blood sugar goes too low.
• Check your blood sugar before driving, and stop if you feel symptoms.

Diet and exercise

Eat a balanced diet with regular meals that include carbohydrates (like whole grains, fruits, and vegetables). If you exercise, you may need to have an extra snack before or after, and adjust your medication as advised by your doctor. Do not skip meals.

Mental health and emotional wellbeing

Hypoglycaemia can cause anxiety, especially if you have had a severe episode. Fear of low blood sugar can affect your quality of life. It is normal to feel worried, and talking to your healthcare provider or a counsellor can help. Remember that you are not alone and that support is available.

Prevention

Many episodes of hypoglycaemia can be prevented by following your treatment plan carefully. Check your blood sugar regularly, eat at regular times, and adjust your medication and food before exercise. If you take insulin, learn how to adjust doses based on your blood sugar and meals. Your healthcare provider can help you create a personalised plan.

Vaccines

Omit

Screening programmes

If you have diabetes, routine blood sugar monitoring is part of your care. If you have symptoms of low blood sugar but do not have diabetes, your doctor may recommend a blood test to check for underlying causes.

Complications

If left untreated

• Loss of consciousness (fainting)
• Seizures or convulsions
• Confusion or behaviour changes
• Accidents or falls due to clumsiness
• Brain damage in very rare, severe cases

Long-term outlook

For most people, hypoglycaemia is a manageable condition. With good awareness and a clear treatment plan, you can quickly correct low blood sugar and prevent it from happening often. Even if you have severe episodes, modern treatments and education can help you stay safe. Many people live full, active lives while managing hypoglycaemia.

Find support

International organisations

• International Diabetes Federation ↗
• Diabetes UK ↗

Local organisations

• NHS – Hypoglycaemia ↗ · United Kingdom

Helplines

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