Mayo Clinic Health Library

Diabetic coma

Updated: 06-19-2012

Definition

A diabetic coma is a life-threatening diabetes complication that causes unconsciousness.

If you have diabetes, dangerously high blood sugar (hyperglycemia) or dangerously low blood sugar (hypoglycemia) can lead to a diabetic coma.

If you lapse into a diabetic coma, you're alive — but you can't awaken or respond purposefully to sights, sounds or other types of stimulation. Left untreated, a diabetic coma can be fatal.

The prospect of a diabetic coma is scary, but fortunately you can take steps to help prevent a diabetic coma. Start by following your diabetes treatment plan.

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Symptoms

Before developing a diabetic coma, you'll usually experience signs and symptoms of high blood sugar or low blood sugar.

High blood sugar (hyperglycemia)
If your blood sugar level is too high, you may experience:

  • Increased thirst
  • Frequent urination
  • Fatigue
  • Nausea and vomiting
  • Shortness of breath
  • Stomach pain
  • Fruity breath odor
  • A very dry mouth
  • A rapid heartbeat

Low blood sugar (hypoglycemia)
Signs and symptoms of blood sugar level may include:

  • Shakiness or nervousness
  • Fatigue
  • Sweating
  • Hunger
  • Nausea
  • Irritability
  • An irregular or racing heartbeat
  • Difficulty speaking
  • Confusion

Some people develop a condition known as hypoglycemia unawareness and won't have the warning signs that signal a drop in blood sugar.

If you experience any symptoms of high or low blood sugar, test your blood sugar and follow your diabetes treatment plan based on the test results. If you don't start to feel better quickly, or you start to feel worse, call for emergency help.

When to see a doctor
A diabetic coma is a medical emergency. If you feel extreme high or low blood sugar symptoms and think you might pass out, call 911 or your local emergency number. If you're with someone with diabetes who has passed out, call for emergency help, and be sure to let the emergency personnel know that the unconscious person has diabetes.

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Causes

Prolonged blood sugar extremes — blood sugar that's either too high or too low for too long — may cause various conditions, all of which can lead to a diabetic coma.

  • Diabetic ketoacidosis. If your muscle cells become starved for energy, your body may respond by breaking down fat stores. This process forms toxic acids known as ketones. Left untreated, diabetic ketoacidosis can lead to a diabetic coma.

    Diabetic ketoacidosis is most common in people who have type 1 diabetes, but it can also affect people who have type 2 diabetes or gestational diabetes.

  • Diabetic hyperosmolar syndrome. If your blood sugar level tops 600 milligrams per deciliter (mg/dL), or 33.3 millimoles per liter (mmol/L), the condition is known as diabetic hyperosmolar syndrome.

    When your blood sugar gets this high, your blood becomes thick and syrupy. The excess sugar passes from your blood into your urine, which triggers a filtering process that draws tremendous amounts of fluid from your body.

    Left untreated, diabetic hyperosmolar syndrome can cause life-threatening dehydration and coma. Diabetic hyperosmolar syndrome is most common in middle-aged and older adults who have type 2 diabetes.

  • Hypoglycemia. Your brain needs glucose to function. In severe cases, low blood sugar may cause you to pass out. Hypoglycemia can be caused by too much insulin or too little food. Exercising too vigorously or drinking too much alcohol can have the same effect.

    Symptoms are influenced by the severity of the hypoglycemia. With longstanding diabetes, however, you may lose the early warning signs — such as hunger and perspiration — and may only develop symptoms when your blood sugar is dangerously low. This is called hypoglycemia unawareness.

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Risk factors

Anyone who has diabetes is at risk of a diabetic coma.

If you have type 1 diabetes, you're more at risk of a diabetic coma caused by:

  • Low blood sugar (hypoglycemia)
  • Diabetic ketoacidosis

If you have type 2 diabetes, you're generally more at risk of a diabetic coma caused by:

  • Diabetic hyperosmolar syndrome, especially if you're middle-aged or older

If you have either type 1 or type 2 diabetes, the following factors can increase the risk of diabetic coma:

  • Insulin delivery problems. If you're on an insulin pump, you have to check your blood sugar frequently, and one of the reasons for this is that a kink in the insulin pump tubing may stop all insulin delivery.

    Even tubeless pumps can sometimes have problems that cause insulin delivery to stop. A lack of insulin can quickly lead to diabetic ketoacidosis if you have type 1 diabetes.

  • An illness, trauma or surgery. When you're sick or injured, blood sugar levels tend to rise, sometimes dramatically. This may cause diabetic ketoacidosis if you have type 1 diabetes and don't increase your insulin intake to compensate.

    Other medical conditions, such as congestive heart failure or kidney disease, may increase your risk of diabetic hyperosmolar syndrome.

  • Poorly managed diabetes. If you don't monitor your blood sugar properly or take your medications as directed, you'll have a higher risk of developing long-term complications and diabetic coma.
  • Deliberately skipping insulin. Sometimes, people with diabetes who also have an eating disorder choose not to use their insulin as directed with the hope of losing weight. This is a dangerous, life-threatening practice that increases the risk of diabetic coma.
  • Drinking alcohol. Alcohol can have unpredictable effects on your blood sugar, sometimes dropping blood sugar levels as long as a day or two after the alcohol was consumed. This can increase your risk of a diabetic coma caused by hypoglycemia.
  • Illegal drug use. Illegal drugs, such as cocaine and Ecstasy, can increase your risk of severe high blood sugar levels, as well as your risk of diabetic coma.
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Complications

Left untreated, a diabetic coma can lead to:

  • Permanent brain damage
  • Death
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Preparing for your appointment

A diabetic coma is a medical emergency that you won't have time to prepare for. If you feel the symptoms of extreme high or low blood sugar, call 911 or your local emergency number to make sure help is on the way before you pass out.

If you're with someone with diabetes who has passed out or is acting extremely strange, possibly as if he or she has had too much alcohol, call for immediate medical help.

What you can do in the meantime
If you have no training in diabetes care, wait for the emergency care team to arrive.

If you are familiar with diabetes care, follow these steps:

  1. Test the unconscious person's blood sugar.
  2. If the blood sugar level is lower than 70 mg/dL (3.9 mmol/L), administer an injection of glucagon. If glucagon isn't available, rub glucose gel, honey or non-sugar-free syrup on the inside of the unconscious person's cheek.  Do not give insulin to someone with low blood sugar.
  3. If the blood sugar level is above 70 mg/dL, wait for medical help to arrive. Don't give sugar to someone whose blood sugar isn't low.
  4. Let the emergency care team know about the diabetes and what steps you've taken, if any.
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Tests and diagnosis

If you experience a diabetic coma, prompt diagnosis is essential. The emergency medical team will do a physical exam and may ask those who are with you about your medical history.

Lab tests
You may need various lab tests to measure:

  • Your blood sugar level
  • Your ketone level
  • The amount of nitrogen or creatinine in your blood
  • The amount of potassium, phosphate and sodium in your blood
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Treatments and drugs

The type of emergency treatment for a diabetic coma depends on whether your blood sugar level is too high or too low.

High blood sugar
If your blood sugar level is too high, you may need:

  • Intravenous fluids to restore water to your tissues
  • Potassium, sodium or phosphate supplements to help your cells function correctly
  • Insulin to help your tissues absorb glucose again
  • Treatment for any underlying infections

Low blood sugar
If your blood sugar level is too low, you may be given a glucagon injection, which will cause your blood sugar level to quickly rise

Consciousness typically returns when blood sugar reaches a normal level.

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Prevention

Good day-to-day control of your diabetes can help you prevent a diabetic coma. Keep these tips in mind:

  • Follow your meal plan. Consistent snacks and meals can help you control your blood sugar level.
  • Keep an eye on your blood sugar level. Frequent blood sugar tests can tell you whether you're keeping your blood sugar level in your target range — and alert you to dangerous highs or lows. Check more frequently if you've exercised because exercise can cause blood sugar levels to drop, especially if you don't exercise regularly.
  • Take your medication as directed. If you have frequent episodes of high or low blood sugar, let your doctor know. He or she may need to adjust the dose or timing of your medication.
  • Have a sick-day plan. Illness can elevate blood sugar unexpectedly. Before you get sick, talk with your doctor about how to best manage this increase in your blood sugar.
  • Check for ketones when your blood sugar is high. Check your urine for ketones when your blood sugar level is more than 240 mg/dL (13.3 mmol/L). If you have a large amount of ketones or they persist, call your doctor for advice. Call your doctor immediately if you have any level of ketones and are vomiting.
  • Have glucagon and fast-acting sources of sugar available. If you take insulin for your diabetes, make sure you have an up-to-date glucagon kit and fast-acting sources of sugar, such as glucose tablets or orange juice, readily available to treat low blood sugar levels.
  • Consider a continuous glucose monitor (CGM), especially if you have trouble maintaining stable blood sugar levels or you don't feel symptoms of low blood sugar (hypoglycemia unawareness).

    CGMs are devices that use a small sensor inserted underneath the skin to track trends in your blood sugar levels and transmit the information to a wireless device.

    These devices can alert you when your blood sugar is dangerously low. However, you still need to test your blood sugar levels using a blood glucose meter even if you're using a CGM. CGMs are more expensive than conventional glucose monitoring methods, but they may help you control your glucose better.

  • Drink alcohol using caution. Because alcohol can have an unpredictable effect on your blood sugar, be sure to have a snack or a meal when you drink, if you choose to drink at all.
  • Educate your loved ones, friends and co-workers. Teach loved ones and other close contacts how to recognize early signs and symptoms of blood sugar extremes — and how to summon emergency help should you pass out.
  • Wear a medical ID bracelet or necklace. If you're unconscious, the ID can provide valuable information to your loved ones, co-workers and others — including emergency personnel.
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