Hyperglycemia refers to high blood sugar, or glucose, levels. The normal fasting range for blood glucose is less than 126mg/dL (milligrams per deciliter); blood glucose higher than 160mg/dL indicates hyperglycemia, according to the Joslin Diabetes Center. Hyperglycemia most often occurs in diabetics, but can also occur when the body is under extreme stress. Taking too little insulin, skipping doses, eating too much and illness can increase the risk of hyperglycemia in diabetics.
Polyuria
Polyuria refers to increased urination. People with hyperglycemia urinate more than usual because the high glucose levels in the kidneys keep fluid from being absorbed, a process called osmotic diuresis. More fluid is therefore eliminated through the kidneys in the form of urine.
Polydipsia
Polydipsia refers to increased thirst. People with hyperglycemia are thirstier than normal because osmotic diuresis results in dehydration as fluid is eliminated from the body, the Merck Manual states. Dehydration can cause weakness and changes in mental status.
Other Symptoms
Fatigue is common in hyperglycemia because cells aren't getting the energy they need from glucose, their primary source of fuel. Instead, the glucose remains in the bloodstream, so people feel tired and lethargic. Dehydration caused by increased urination and osmotic diuresis also causes fatigue. Hyperglycemia can cause blurred vision, which may improve as blood sugar levels drop. Hyperglycemics may feel increased hunger because their cells aren't absorbing the glucose that normally gives them energy. The cells signal that they need nutrition, and the person feels hungry. Weight loss can result even when the person is eating enough food.
Ketoacidosis
Very high blood glucose can cause ketoacidosis, a condition where body fats called ketones are broken down to be use for energy, as glucose is not being absorbed into the cells. Symptoms of ketoacidosis include a fruity smell to the breath, dry mouth, extreme thirst and deep rapid breathing known as Kussmaul breathing. If ketoacidosis isn't treated, the patient goes into a coma. Ketoacidosis is a medical emergency and needs prompt treatment with insulin to lower the blood sugar.
