Diabetic Coma

Overview

A diabetic coma is a state of deep unconsciousness that can happen to someone with diabetes when their blood sugar moves far outside the safe range. Blood sugar (also called glucose) is the main fuel your body uses for energy. If it drops dangerously low, or rises dangerously high, the brain cannot work properly, and the person can become sleepy, confused, and finally unresponsive. A diabetic coma is a medical emergency, but it can usually be prevented with good day-to-day diabetes care, and people who get help quickly often recover well.

It is uncommon. Most people with diabetes never experience a coma, and modern home blood sugar testing and education have made it even rarer. When it does happen, it is most often linked to severe low blood sugar or to a high-sugar emergency called diabetic ketoacidosis (a build-up of harmful acids in the blood) or a very high-sugar state with severe dehydration.

It can affect anyone with diabetes, at any age. It is seen most often in people who take insulin, in children and young adults with type 1 diabetes, and in older adults with type 2 diabetes who become unwell or dehydrated. People who live alone, have memory problems, drink heavily, or have limited access to healthcare may be at higher risk because early signs are easier to miss.

Symptoms

Common symptoms

• Feeling very thirsty and needing to pass urine much more often than usual
• Shaking, sweating, fast heartbeat, or sudden hunger (signs of low blood sugar)
• Confusion, difficulty concentrating, slurred speech, or odd behaviour
• Feeling very tired, weak, or unusually sleepy
• Feeling or being sick, or pain in the tummy
• Fast, deep breathing and breath that smells fruity or like nail polish remover
• Blurred vision, dizziness, or feeling faint
• Becoming less responsive, difficult to wake, or unresponsive

Symptoms in children

• Tummy pain and vomiting, which can be mistaken for a stomach bug
• Fast or deep breathing
• Fruity-smelling breath
• Unusual sleepiness, irritability, or crying that is hard to soothe
• Wetting the bed again after being dry, or much more thirst and urination
• Staring, floppiness, or not responding normally to you

Symptoms in older adults

• New or worsening confusion that may be mistaken for dementia or 'just old age'
• Weakness, unsteadiness, or a fall
• Very high blood sugar with thirst that seems mild, because thirst can be blunted with age
• Dry mouth, sunken eyes, or passing much less urine (signs of dehydration)
• Drowsiness or difficulty staying awake

Causes

Main causes

• Very low blood sugar, often from too much diabetes medicine for the amount of food eaten, missed meals, unusual exercise, or alcohol
• Very high blood sugar with a build-up of harmful acids (diabetic ketoacidosis), most often in type 1 diabetes
• Very high blood sugar with severe dehydration (sometimes called a hyperosmolar state), more often in type 2 diabetes
• Serious illness or infection, which pushes blood sugar out of balance
• Missing or running out of diabetes medicine, or a problem with an insulin pump or pen

Risk factors

• Living with type 1 diabetes, or taking insulin for type 2 diabetes
• Previous episodes of very low or very high blood sugar
• Not checking blood sugar regularly, or not recognising the early warning signs
• Being unwell with an infection, or having a heart attack or stroke
• Alcohol use, especially drinking without eating
• Being older and living alone, or having memory problems
• Kidney disease, or other long-term conditions
• Limited access to diabetes supplies, food, or medical care

When to see a doctor

See a doctor urgently if:

• Your blood sugar is often very high or very low and you cannot work out why
• You have had a low blood sugar episode that needed someone else's help
• You are vomiting, have tummy pain, or cannot keep fluids down
• You feel confused, very sleepy, or more unwell than usual
• You are ill with an infection and your blood sugar is hard to control

Book a routine appointment if:

• You want to review your blood sugar patterns or your sick-day plan
• You are unsure how to recognise or treat low blood sugar
• You would like a refresher on how to check for ketones
• You are planning travel, shift work, or a change in routine and want advice
• You feel worried or worn down by managing diabetes

Diagnosis

Doctors usually recognise a diabetic coma quickly from what family or carers describe, plus a bedside blood sugar reading. The key next step is working out whether the cause is low blood sugar or high blood sugar, because the treatments are very different. While the person is being stabilised, the medical team runs blood and urine tests to check for harmful acids, dehydration, and any infection or illness that may have triggered the problem.

Tests that may be done

• Blood sugar reading, often from a finger prick and then confirmed with a lab blood test
• Blood or urine tests for ketones (harmful acids that build up when the body lacks fuel)
• Blood tests to check the body's salt balance and acid levels
• Kidney function and blood count tests
• A heart tracing, if the heart rhythm needs checking
• Tests to look for infection, such as a chest X-ray or urine test
• In some cases, a scan of the head to rule out other causes of unconsciousness

What to expect at your appointment

This is an emergency, so care happens fast. The person is usually treated in an emergency department or intensive care area. Family members may be asked what happened, what medicines the person takes, and when they last ate or checked their blood sugar — these details genuinely help the team. Once the person is stable, the team will talk through what caused the episode and how to lower the chance of it happening again.

Treatment

Treatment happens in hospital and focuses on three things: protecting the person's breathing and safety, bringing blood sugar back into a safe range slowly and carefully, and finding and treating whatever set the problem off. Most people wake up and improve within hours to a day or two once treatment starts, though some need to stay in hospital longer, especially if they had an infection.

Self-care at home

• Check your blood sugar as often as your care team advises, and more often when you are ill, stressed, or exercising
• Learn the early signs of low and high blood sugar, and teach the people around you
• Carry a fast source of sugar with you in case of low blood sugar
• Wear or carry medical ID saying you have diabetes
• Follow your agreed sick-day plan: keep checking, keep hydrated, and ask for advice early if you are unwell
• Keep spare supplies, and make sure your medicines are in date and never run out
• Tell your diabetes team if you have had a severe low or high episode, so your plan can be reviewed

Medical treatments

In hospital, the care team supports breathing and circulation, gives fluids through a drip to treat dehydration, and corrects blood sugar gradually — bringing it down or up slowly is safer than a sudden change. They also correct the body's salt and acid balance, treat any infection, and monitor the heart and brain closely. Once the person is alert and stable, the team looks at why it happened and adjusts the diabetes plan, along with practical teaching for the person and their family.

When is surgery considered?

Surgery is not used to treat a diabetic coma. Rarely, someone who becomes unconscious for another reason, such as a head injury or a serious infection, may need an operation — but that would be for the other problem, decided by the medical team.

Living with this condition

Life after a coma episode usually means a closer look at routines rather than a complete change of direction. Many people find that a simple daily rhythm — checking blood sugar at set times, eating regular meals, and knowing what to do when things feel off — brings back confidence quickly. It is normal to feel shaken for a while, and having a written plan on the fridge or in your phone can be very calming for you and for the people you live with.

Lifestyle tips

• Keep a regular pattern of meals and sleep where you can
• Plan ahead for exercise by checking blood sugar before, during, and after
• Be careful with alcohol, especially drinking on an empty stomach
• Keep a small card listing your medicines and emergency contacts
• Make sure a friend, neighbour, or family member knows how to help in an emergency
• Store diabetes supplies where you can reach them easily, and replace them before they run out

Diet and exercise

There is no single 'diabetes diet'. Eating regular meals with plenty of vegetables, some whole grains, and protein, and limiting very sugary drinks, helps keep blood sugar steadier. Movement — walking, swimming, cycling, or whatever you enjoy — helps your body use sugar better. If you take insulin or tablets that can cause low blood sugar, exercise can drop your levels, so check before and after and keep a fast source of sugar with you.

Mental health and emotional wellbeing

A coma or a severe low blood sugar episode can leave you feeling frightened and less confident, and some people become very anxious about their blood sugar. That is understandable and worth talking about — you do not have to manage it alone. If you feel low, panicky, or hopeless, please tell your diabetes team or doctor; support is available and it helps. If you ever have thoughts of harming yourself, contact your local emergency number or a crisis support service in your country straight away.

Prevention

Most episodes can be prevented, and this is genuinely encouraging. The main steps are checking blood sugar regularly, recognising the early warning signs, following a sick-day plan, and asking for help early when something feels wrong. Make sure your diabetes team reviews your plan after any severe episode, and never stop or change your medicines without advice.

Vaccines

Because infections can push blood sugar badly out of balance, people with diabetes are usually advised to keep up with routine vaccinations, such as flu and pneumonia vaccines. Ask your doctor or pharmacist which vaccines are recommended for you and when.

Screening programmes

Regular diabetes reviews are your best safety net. These usually include a check of your average blood sugar over time, blood pressure, cholesterol, kidney tests, and eye and foot checks. Between visits, review your home blood sugar readings with your team so patterns can be spotted early.

Complications

If left untreated

• Brain injury from severely low blood sugar or from severe dehydration
• Dangerous heart rhythm problems or a drop in blood pressure
• Swelling of the brain, which is rare but is seen more often in children
• Blood clots, or infection in the lungs from breathing in vomit
• Kidney injury
• Loss of life — which is why a diabetic coma must be treated as an emergency

Long-term outlook

The outlook is generally good when help arrives quickly. Many people recover fully and are back to their usual selves within days. Having one episode does not mean it will happen again — with a review of your diabetes plan, good education, and support from your care team, most people go on to live full, active lives. If you have had a severe episode, your team will want to see you soon to make your plan safer.

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