A diabetic coma is a life-threatening emergency that can affect anyone living with diabetes. It happens when blood sugar levels become dangerously high or dangerously low. The good news is that with the right knowledge and a solid diabetes management plan, this complication is largely preventable. This article explains what causes a diabetic coma, what symptoms to watch for, and what Canadian families should know to stay safe.
What Is a Diabetic Coma?
A coma is a state of prolonged unconsciousness. A person in a coma is alive but cannot be woken up and does not respond to sights, sounds, or touch. A diabetic coma occurs when extreme blood sugar levels — either too high or too low — cause the brain to stop functioning normally.
Left untreated, a diabetic coma can cause permanent brain damage or death. However, when caught early and treated quickly, most people recover fully. The overall risk of diabetic coma is relatively low, especially for people who manage their diabetes carefully.
How Your Body Normally Controls Blood Sugar
Understanding blood sugar control helps explain why a diabetic coma happens. Your body works hard to keep glucose levels in a safe range at all times.
The Role of Insulin and Glucagon
Two hormones made by the pancreas control blood sugar. Insulin lowers blood sugar by helping cells absorb glucose after a meal. Glucagon raises blood sugar between meals by signalling the liver to release stored glucose.
In a healthy body, these two hormones balance each other perfectly. When you eat, insulin rises and glucagon falls. When you fast or exercise, glucagon rises and insulin falls. In diabetes, this balance breaks down.
What Happens When Blood Sugar Drops Too Low
When blood sugar falls, the body triggers a chain reaction to bring it back up. First, insulin secretion drops. Then glucagon rises, prompting the liver to produce more glucose. Adrenaline is also released, which has a similar effect. If blood sugar stays low for several hours, the body also releases cortisol and growth hormone to further protect glucose levels.
In people with diabetes, this counter-regulation system may not work properly. As a result, blood sugar can drop to dangerous levels without the body correcting itself in time.
Types of Diabetic Coma: Causes and Mechanisms
There are two main types of diabetic coma, each caused by a different blood sugar problem.
Hyperglycemic Coma (High Blood Sugar)
A hyperglycemic coma occurs when blood sugar rises far above normal. This can happen in two forms: diabetic ketoacidosis (DKA), which is more common in Type 1 diabetes, and hyperosmolar hyperglycemic state (HHS), which is more common in Type 2 diabetes.
In both cases, the body lacks enough insulin to use glucose properly. Without insulin, glucose builds up in the blood. The body then breaks down fat for energy, which produces toxic acids called ketones. High ketone levels, combined with severe dehydration, can lead to a diabetic coma.
Furthermore, the body releases stress hormones — including adrenaline, cortisol, and growth hormone — that make the situation worse. These hormones raise blood sugar even further and increase ketone production.
Hypoglycemic Coma (Low Blood Sugar)
A hypoglycemic coma occurs when blood sugar drops so low that the brain cannot function. The brain relies almost entirely on glucose for energy. When glucose runs out, brain activity shuts down rapidly.
This type of diabetic coma most often affects people who take insulin or a class of medication called sulfonylureas. It can happen if too much insulin is taken, if a meal is skipped, or if the body’s response to low blood sugar is impaired.
Risk Factors and Triggers
Knowing your risk factors can help you and your family doctor create a prevention plan. Several situations can trigger a diabetic coma.
Triggers for High Blood Sugar Coma
Missing insulin doses or taking doses that are too small
Infections — including urinary tract infections, pneumonia, or stomach illness — which raise stress hormones
Newly diagnosed diabetes that has not yet been treated
Stroke or heart attack, both of which stress the body
Acute pancreatitis, often linked to heavy alcohol use
Certain medications, including some steroids and diuretics
Hormonal disorders such as Cushing’s syndrome or an overactive thyroid
Problems with insulin pumps, such as a blocked catheter or a leaking infusion set
Triggers for Low Blood Sugar Coma
Long duration of diabetes — the longer you have had diabetes, the harder it can be to feel low blood sugar coming
Skipping meals or eating too few carbohydrates
Drinking alcohol, which blocks the liver from releasing glucose
Unusual or intense physical activity without adjusting food or medication
Chronic kidney disease, which slows the breakdown of insulin
Recent episodes of low blood sugar, which can blunt your body’s warning signals
Hypoglycaemia unawareness — not feeling the usual symptoms when blood sugar drops
Warning Signs and Symptoms
A diabetic coma does not happen without warning. Before losing consciousness, a person will usually show signs of either high or low blood sugar. Acting on these early symptoms is the key to preventing a coma.
Symptoms of High Blood Sugar (Hyperglycaemia)
If blood sugar is rising dangerously, a person may experience:
Extreme thirst
Frequent urination
Dry mouth
Nausea and vomiting
Shortness of breath or fruity-smelling breath
Fatigue and confusion
Symptoms of Low Blood Sugar (Hypoglycaemia)
If blood sugar is dropping dangerously, a person may experience:
Shaking or trembling
Sweating
Intense hunger
Irritability or anxiety
Confusion or difficulty concentrating
Weakness or extreme fatigue
In both cases, if these symptoms are not treated quickly, the person may lose consciousness. That is when a diabetic coma becomes a medical emergency. Learn more about diabetic coma symptoms at Mayo Clinic.
When to See a Doctor
If someone loses consciousness and you suspect a diabetic coma, call 911 immediately. Do not try to give food or drink to an unconscious person. If the person wears a medical alert bracelet, tell the emergency dispatcher.
For non-emergency concerns, speak with your family doctor or visit a walk-in clinic. If you have diabetes and experience frequent episodes of low or high blood sugar, your doctor can review your medication, your diet, and your monitoring routine. Most provincial health plans in Canada cover regular diabetes check-ups and blood tests, so do not hesitate to use those benefits.
You should also talk to your doctor if you notice that you are no longer feeling the usual warning signs of low blood sugar. This condition, called hypoglycaemia unawareness, increases your risk of a diabetic coma significantly. Health Canada provides guidance on insulin safety and diabetes management.
Diagnosis and Emergency Treatment
In a hospital emergency, doctors and nurses will act fast. They will perform a physical exam and check your medical history with the help of family members if needed.
Diagnostic Tests
Emergency teams will typically measure:
Blood glucose levels — to confirm whether sugar is too high or too low
Ketone levels — elevated ketones point to diabetic ketoacidosis
Creatinine and nitrogen — to check how well the kidneys are working
Haematocrit — the proportion of red blood cells in the blood
Potassium levels — which are often disrupted during a diabetic crisis
Emergency Treatment
Treatment depends on whether the coma is caused by high or low blood sugar. For high blood sugar, doctors give intravenous fluids to reverse dehydration and insulin to bring glucose levels down. Supplements of potassium, sodium, and chloride are often needed to restore the body’s electrolyte balance.
For low blood sugar, treatment is faster. Doctors give intravenous glucose directly. If the person is not yet unconscious but is unable to swallow safely, a glucagon injection may be used. Recovery from a hypoglycaemic coma can begin within minutes of treatment.
Preventing a Diabetic Coma
Prevention is the most important part of diabetic coma management. The risk is small when diabetes is well controlled. Here is what you can do to protect yourself.
Monitor your blood sugar regularly, especially when you are sick, stressed, or more active than usual
Take your medication as prescribed and never skip doses without talking to your doctor first
Eat regularly and do not skip meals, especially if you take insulin or sulfonylureas
Carry fast-acting sugar — such as glucose tablets or juice — in case your blood sugar drops
Limit alcohol and always eat food when you drink
Wear a medical alert bracelet so emergency responders know you have diabetes
Teach family members how to use a glucagon emergency kit
Check your insulin pump regularly for blockages or leaks if you use one
Following your diabetes care plan is the single most effective way to prevent a diabetic coma. Healthline offers further reading on preventing hyperglycaemic emergencies.
Frequently Asked Questions
What is a diabetic coma?
A diabetic coma is a life-threatening state of unconsciousness caused by extremely high or extremely low blood sugar. A person in a diabetic coma is alive but cannot be woken up or respond to their surroundings. It is a medical emergency that requires calling 911 immediately.
What are the warning signs before a diabetic coma?
Before a diabetic coma occurs, a person will usually show signs of high or low blood sugar. High blood sugar symptoms include extreme thirst, frequent urination, nausea, and shortness of breath. Low blood sugar symptoms include shaking, sweating, confusion, and intense hunger.
How long can a person be in a diabetic coma?
The length of a diabetic coma depends on how quickly treatment is received. With prompt emergency care, many people recover within hours. However, if a diabetic coma is left untreated for an extended period, it can cause permanent brain damage or death.
Can a diabetic coma happen during sleep?
Yes, a diabetic coma can occur during sleep, particularly from low blood sugar (nocturnal hypoglycaemia). This is more common in people who take insulin. Checking blood sugar before bed and following your doctor’s advice about nighttime snacks can help reduce this risk.
Is a diabetic coma covered under provincial health plans in Canada?
Yes, emergency treatment for a diabetic coma — including hospitalization, intravenous fluids, and insulin — is covered under all provincial and territorial health plans in Canada. Preventive care, including regular blood sugar monitoring and diabetes management appointments, is also covered under most plans.
What should I do if someone with diabetes loses consciousness?
If someone with diabetes loses consciousness, call 911 right away. Do not try to give them food or drink. If you have been trained to use a glucagon emergency kit, administer it while waiting for help. Tell the emergency dispatcher that the person has diabetes so responders can prepare the right treatment.
Key Takeaways
A diabetic coma is a serious but largely preventable complication of diabetes. It is caused by blood sugar that is either dangerously high (hyperglycaemia) or dangerously low (hypoglycaemia). Warning signs always appear before a coma — knowing them and acting fast can save a life. If someone loses consciousness, call 911 immediately. Do not wait. Regular check-ups with your family doctor or at a walk-in clinic are key to preventing this emergency. Following your diabetes management plan — including medication, meals, and blood sugar monitoring — is the best protection available. Always speak with a qualified healthcare provider about your personal
