What Do Dangerous Blood Sugar Levels Mean for Diabetics?

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Dangerous blood sugar levels occur most commonly in people with type 1 diabetes mellitus and are less common in people with type 2 diabetes. People with type 1 diabetes produce little or no insulin. Without supplemental insulin, a sequence of physiologic changes occurs that leads to a condition called ketoacidosis. Ketoacidosis requires hospitalization and intensive treatment to prevent life-threatening complications or even death.


When a diabetic has little or no insulin, glucose can’t enter cells. This state of “cell starvation” causes the body to produce hormones that break down fat as an alternative form of fuel for glucose-deprived cells to use. When these fats break down, they form acidic compounds called ketone bodies that most cells can use as a source of energy. When acidic ketone bodies form in large quantities it causes the blood to become too acidic, which leads to changes in electrolytes such as potassium, sodium, and bicarbonate. These changes can be life-threatening if not promptly treated.

People with dangerous blood sugar levels and ketoacidosis are frequently low in potassium, sodium and chloride levels due the effects of the acidic ketone bodies. They’re also usually critically dehydrated and require replenishment of electrolytes along with the replacement of fluids.

People with ketoacidosis also need insulin to stop more ketones from forming and correct the high blood sugar levels. This requires hospitalization for I.V. fluid, insulin and electrolyte replacement – and very close monitoring. Dangerous blood sugar levels are usually slowly brought down with intravenous insulin.

The Risks of Ketoacidosis

If ketoacidosis isn’t promptly treated or treated improperly, several complications can develop. Low potassium levels can trigger dangerous, and sometimes fatal, heart rhythms. Low sodium levels can also lead to swelling in the brain, which can have serious, long-term effects on brain function.

People with ketoacidosis are usually severely dehydrated, which can cause drops in blood pressure and, in some cases, shock followed by death.

Treatment of Dangerous Blood Sugar Levels and Ketoacidosis

Treatment focuses on replacing the lost fluids, electrolytes and correcting the high blood sugar levels with insulin. Replacement of lost fluid is done at a gradual, controlled rate since rapid fluid replacement increases the risk of brain swelling. Fortunately, the death rate from ketoacidosis is less than 5% these days - thanks to improvements in treatment.

It’s important to investigate what triggered the dangerous blood sugar levels and ketoacidosis. Pregnancy, heart attack, stroke, alcohol abuse, extreme stress and the use of certain drugs can bring on ketoacidosis in a previously well-controlled diabetic. Ketoacidosis can also be the first indication that a person has type 1 diabetes.

At what blood sugar level does ketoacidosis become a concern? Most doctors recommend checking your urine for ketones when your blood sugar rises above 240 mg/dl and every five hours if you’re ill, especially if you’re vomiting. Always call your doctor if your urine shows ketones or if you’re sick. The blood sugar level at which ketoacidosis occurs varies with the individual.

Diabetics can also have dangerous blood sugar levels without ketosis, a condition called hyperosmolar hyperglycemic nonketotic syndrome that usually occurs in type 2 diabetics who have an infection or other illness, and they’re not drinking enough fluids. Symptoms may appear when blood sugars reach 600 mg/dl. or above, and the mortality can be as high as 20% if treatment isn’t prompt. Always monitor blood sugars closely, and drink plenty of fluids when you’re ill.

Low Blood Sugars Can Be Dangerous Too

People who take insulin therapy are at risk for developing dangerous blood sugar levels of another type - very low ones. Low blood sugar levels can be even more deadly than high ones, at least in the short-term. Hypoglycemia is more common in type 1 diabetics who take insulin and in people with type 2 diabetes who take certain types of diabetes medications that stimulate insulin release.

It’s critical that a diabetic learn to recognize the symptoms of hypoglycemia and have a source of glucose readily available to raise blood sugar levels quickly should hypoglycemia occur. Symptoms of hypoglycemia such as weakness, lightheadedness, shakiness, headache and hunger usually appear when blood sugars drop below 70 mg/dl. Low blood sugar generally doesn’t become dangerous until it drop below 50 mg/dl.

Drops in blood sugar usually occur when a diabetic isn’t eating regular meals, exercising more than usual or is taking too much insulin or diabetes medication. If you have a hypoglycemic episode, treat it quickly, and call your doctor. Your doctor may advise making adjustments to your diet or insulin regimen.

The Bottom Line?

Ketoacidosis is a life-threatening complication of type 1 diabetes, and much less commonly, type 2 diabetes. It’s a condition that needs immediate hospitalization and treatment to avoid serious complications or even death. All type 1 diabetics need to be closely monitored for signs and symptoms of ketoacidosis – and prompt action is needed if they develop.


Merck Manual. Eighteen edition. 2006.

EMedicine. “Diabetic Ketoacidosis”

Diabetes Care. 29(12): 2739-48.