Low Blood Sugar Hypoglycaemia

Overview

Low blood sugar — doctors call it hypoglycaemia (say: hy-po-gly-SEE-mee-ah) — means the level of sugar (glucose) in your blood has dropped too low. Glucose is the main fuel your body and brain use, so when it falls, you can feel shaky, confused or very tired. In the UK, a level below about 4 mmol/L is usually called a low. It is most common in people who take medicines for diabetes, but it can happen for other reasons too.

Yes, it is common — especially among people with type 1 diabetes, and among some people with type 2 diabetes who take certain medicines. People who do not have diabetes rarely get low blood sugar.

It mostly affects people with diabetes who use insulin or tablets that lower blood sugar. It can also affect people who drink a lot of alcohol without eating, people with kidney or liver problems, and, rarely, people with certain hormone conditions. Very tight blood sugar control, skipped meals and strenuous exercise raise the chance of a low.

Symptoms

Common symptoms

• Feeling shaky or trembling
• Sweating, often cold and clammy
• A fast or pounding heartbeat
• Feeling very hungry
• Tingling or numbness around the lips and tongue
• Looking pale
• Feeling irritable, anxious or tearful
• Dizziness or light-headedness
• Blurred vision
• Difficulty concentrating or feeling confused
• Feeling weak or unusually sleepy

Symptoms in children

• Behaviour that is unusual for them — tantrums, clinginess or sudden tearfulness
• Being pale, sweaty or shaky
• Feeling very hungry or complaining of a tummy ache
• Being unusually sleepy, quiet or hard to wake
• Refusing food or being sick
• Night-time lows can cause bad dreams, crying out, or waking up sweaty with a headache

Symptoms in older adults

• Confusion or muddled thinking that can be mistaken for dementia or a stroke
• Feeling drowsy or unusually slow
• Falls or problems with balance
• Fewer or no early warning signs, so a low can be missed until it is more serious
• Weakness or feeling generally unwell rather than the classic shaky, sweaty picture

Causes

Main causes

• Diabetes medicines that lower blood sugar — taking too much, or taking the usual amount when you need less
• Missing, delaying or eating less than usual at a meal
• Drinking alcohol, especially on an empty stomach — alcohol can block your body from raising blood sugar
• Extra or unplanned physical activity without adjusting food or medicines
• Being unwell with vomiting, diarrhoea or infection, which affects eating and blood sugar
• Kidney or liver problems, which can make low blood sugar more likely
• Some other medicines, including certain heart and antibiotic medicines, can occasionally cause lows
• Rarely, conditions where the body makes too much of its own insulin-like hormones

Risk factors

• Having type 1 diabetes
• Having type 2 diabetes and taking insulin or tablets that can cause lows
• Very tight blood sugar control, or aiming for low targets
• Being older, or having memory problems that make it easy to forget meals or repeat a dose
• Long-standing diabetes, which can blunt your warning signs
• Drinking a lot of alcohol
• Being pregnant
• Doing long or intense exercise, especially without eating beforehand
• Poor sleep, stress or a busy day that disrupts your usual routine

When to see a doctor

See a doctor urgently if:

• You have had a severe low needing someone else's help, or you passed out
• Your warning signs have become weak or disappeared
• You are having lows more than once a week
• A low happened at night, or you woke up with a headache and sweaty sheets
• Your blood sugar keeps dropping below your target despite following your plan

Book a routine appointment if:

• You want to review your medicine routine or blood sugar targets
• You are planning pregnancy, a long trip, or a big change in exercise
• You want advice on testing your blood sugar more or less often
• You feel anxious about lows and want help feeling more confident
• You are not sure how to treat a low correctly

Diagnosis

If you have diabetes, low blood sugar is usually confirmed by testing your blood with your meter or sensor at the time you feel unwell, and seeing a low reading that improves after you eat sugar. If the cause is unclear, or you do not have diabetes, your doctor will ask about your symptoms, medicines, meals and alcohol, and may arrange blood tests.

Tests that may be done

• A finger-prick blood sugar test or a reading from a continuous glucose sensor
• A blood test taken in the lab to confirm a low blood sugar level
• A longer-term blood test (often called HbA1c) to see your average sugar levels
• A review of all your medicines, including ones bought over the counter
• Blood tests to check kidney, liver and thyroid function
• In rare cases, a supervised fasting test or referral to a specialist

What to expect at your appointment

Your appointment is mostly a conversation. Your doctor or nurse will look at your recent readings, ask when and how often lows happen, and check whether your medicines and daily routine fit together. You may be asked to keep a simple diary of meals, activity, alcohol and readings for a week or two. Any changes to your treatment will be explained and planned with you, never made without your agreement.

Treatment

Treatment depends on whether the low is mild or serious. A mild low is treated with a small amount of fast-acting sugar, then a snack or meal to keep your levels steady. Serious lows need help from someone else and, sometimes, emergency medical care. Alongside this, your healthcare team will look at why lows are happening and adjust your routine, food and medicines to prevent them.

Self-care at home

• Treat a mild low straight away with fast-acting sugar — for example a few glucose tablets, half a glass of fruit juice or a sugary (not diet) drink, or a spoonful of sugar or honey. Follow your own team's advice.
• Wait about 10 to 15 minutes, then test again. If you are still low, repeat the sugar.
• Once you feel better, eat a longer-lasting snack or your next meal, such as a sandwich, to stop the low coming back.
• Sit down and rest while you treat a low, and do not drive until your level is back to normal and at least 45 minutes have passed — check your own country's driving rules.
• Carry fast-acting sugar with you at all times, and keep some by your bed and in your bag or car.
• Wear or carry medical ID, and make sure the people you live and work with know what to do.
• Keep a simple note of when lows happen, so patterns are easier to spot.

Medical treatments

Your healthcare team will usually start by reviewing the timing and type of your diabetes treatment, your meal pattern and your activity levels, and may suggest changes to reduce lows. They may also teach you a structured education course about managing your blood sugar. If you are at risk of severe lows, your team may prescribe an emergency treatment that a family member or friend can give if you cannot swallow safely — they will explain exactly when and how to use it, and train the people around you. Never change or stop any medicine on your own; always talk to your team first.

When is surgery considered?

Surgery is not a treatment for low blood sugar. Very rarely, if tests show a growth in the pancreas is making too much insulin, a specialist team may discuss an operation — this is uncommon and would always be explained fully by the specialist.

Living with this condition

Life with low blood sugar is mostly about rhythm: regular meals, knowing your warning signs, and having sugar within reach. It can feel like a lot to think about at first, but most people settle into a routine that fits their life. Build a small safety kit — sugar, a meter or sensor, and medical ID — and keep it wherever you go.

Lifestyle tips

• Eat meals at regular times and do not skip breakfast, especially if you take diabetes medicines
• If you drink alcohol, eat something first and check your blood sugar before bed — lows can happen many hours later
• Check your levels before, during and after unusual or long exercise
• Tell friends, family and colleagues what your warning signs look like and how to help
• Set reminders on your phone for medicines and meals if you tend to forget
• Keep fast-acting sugar in the car, at work, in your bag and by your bed
• Have a sick-day plan from your team for when you cannot eat normally

Diet and exercise

There is no special diet for low blood sugar — a balanced, regular way of eating is what matters most. Try to include some slower-release carbohydrate, such as wholegrain bread, oats, rice or potatoes, at each meal to keep levels steadier. Exercise is good for you and helps your body use sugar better, but it can also lower blood sugar for up to a day afterwards. Check your level before you start, take sugar with you, and ask your team how to adjust food or medicines around activity.

Mental health and emotional wellbeing

It is very normal to feel anxious or wary after a low, and some people become afraid of exercise, sleep or being alone. That fear can make it harder to manage diabetes well, which is frustrating and understandable. Talk to your team — there is a lot they can do to reduce lows and rebuild confidence. If you ever feel you cannot cope, or you have thoughts of harming yourself, contact your local crisis line or your local emergency number straight away, or speak to a doctor you trust.

Prevention

Often, yes. Most lows can be made much less frequent by matching your medicines, meals and activity, checking your levels at key times, and having a plan for alcohol, exercise and sick days. No plan removes every low, but good preparation makes them shorter, milder and less frightening.

Screening programmes

If you take diabetes medicines that can cause lows, your team should review your levels, your low-sugar episodes and your targets at least once a year, and more often if you are having problems. Regular eye, kidney and foot checks are also part of good diabetes care.

Complications

If left untreated

• A severe low that leads to a seizure, unconsciousness or a coma
• Falls and injuries, especially in older adults
• Confusion that can be mistaken for drunkenness or a stroke
• Lows during sleep that go unnoticed
• Fear of lows leading to higher blood sugar and less good long-term control
• In pregnancy, poorly managed lows can affect both you and your baby

Long-term outlook

The outlook is good. Most people who learn their warning signs and keep fast-acting sugar to hand manage lows safely and carry on with normal life. Teams today have many ways to reduce lows, including newer technology and gentler targets, so if lows are a problem for you, it is worth asking for a review — there is usually something that can be improved.

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