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

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 a low blood sugar level may include:

• Shakiness or nervousness
• Anxiety
• Fatigue
• Weakness
• Sweating
• Hunger
• Nausea
• Dizziness or lightheadedness
• Difficulty speaking
• Confusion

Some people, especially those who've had diabetes for a long time, 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 signs or 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.

Blood sugar that's either too high or too low for too long may cause various serious 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. If you have ketones (measured in blood or urine) and high blood sugar, the condition is called diabetic ketoacidosis. Left untreated, it can lead to a diabetic coma.

  Diabetic ketoacidosis is most common in type 1 diabetes but sometimes occurs in 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 called diabetic hyperosmolar syndrome.

  Severely high blood sugar turns your blood 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, this can lead to life-threatening dehydration and a diabetic coma. About 25 to 50 percent of people with diabetic hyperosmolar syndrome develop a coma.

• 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 not enough food. Exercising too vigorously or drinking too much alcohol can have the same effect.

Anyone who has diabetes is at risk of a diabetic coma, but the following factors can increase the risk:

• Insulin delivery problems. If you're on an insulin pump, you have to check your blood sugar frequently. Insulin delivery can stop if the pump fails or the tubing (catheter) is twisted or falls out of place. A lack of insulin can lead to diabetic ketoacidosis.

• 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 dosage to compensate.

  Medical conditions, such as congestive heart failure or kidney disease, also 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 a diabetic coma.
• Deliberately skipping meals or 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 a diabetic coma.
• Drinking alcohol. Alcohol can have unpredictable effects on your blood sugar. Alcohol's sedating effects may make it harder for you to know when you're having low blood sugar symptoms. 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 and conditions linked to diabetic coma.

Left untreated, a diabetic coma can lead to:

• Permanent brain damage
• Death

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, even hours later, 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 the timing of your medication.
• Have a sick-day plan. Illness can cause an unexpected change in blood sugar. If you are sick and unable to eat, your blood sugar may drop. Before you get sick, talk with your doctor about how to best manage your blood sugar levels. Consider storing at least three days' worth of diabetes supplies and an extra glucagon kit in case of emergencies.
• Check for ketones when your blood sugar is high. Check your urine for ketones when your blood sugar level is over 250 mg/dL (14 mmol/L) on more than two consecutive tests, especially if you are sick. If you have a large amount of ketones, call your doctor for advice. Call your doctor immediately if you have any level of ketones and are vomiting. High levels of ketones can lead to diabetic ketoacidosis, which can lead to coma.
• 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 or if it is dropping too fast. 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 with 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 the early signs and symptoms of blood sugar extremes and how to give emergency injections. If you pass out, someone should be able to call for emergency help.
• Wear a medical ID bracelet or necklace. If you're unconscious, the ID can provide valuable information to your friends, co-workers and others — including emergency personnel.

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. If you have diabetes, you may want to wear a medical ID bracelet or necklace.

Lab tests

At the hospital, 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

Diabetic coma requires emergency medical treatment. The type of treatment 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 the glucose in your blood
• 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. Intravenous dextrose also may be given to raise blood glucose levels.

A diabetic coma is a medical emergency that you won't have time to prepare for. If you feel the symptoms of extremely 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 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, test the unconscious person's blood sugar and follow these steps:

• If the blood sugar level is lower than 70 mg/dL (3.9 mmol/L), give the person an injection of glucagon. Do not try to give fluids to drink and do not give insulin to someone with low blood sugar.
• If the blood sugar level is above 70 mg/dL (3.9 mmol/L) wait for medical help to arrive. Don't give sugar to someone whose blood sugar isn't low.
• If you called for medical help, let the emergency care team know about the diabetes and what steps you've taken, if any.