What Is Considered A High Level of Serum Glucose?

Glucose is required by the body to maintain life. However, it is possible to have too much of a good thing. Hyperglycemia, or high blood glucose levels, may be due to diabetes, medications, stress, illness, hyperthyroidism, Cushing syndrome, pancreatitis or pancreatitis cancer. It is important to know the symptoms of high blood glucose and to see your doctor immediately if you experience any signs to prevent further complications.

Checking blood with a glucose meter Credit: Trepalio/iStock/Getty Images

Glucose Levels

A fasting blood glucose test is usually the first step to determining if you have high blood glucose levels, according to the National Institute of Diabetes and Digestive and Kidney Diseases. It is most reliable when done in the morning, after you have fasted for at least eight hours. Normal levels should be below 99 mg/dL. Pre-diabetes is diagnosed when levels are between 100 to 125 mg/dL. Diabetes is confirmed if your fasting blood glucose levels are 126 mg/dL or above on repeated tests. Random or nonfasting blood glucose levels of above 200 mg/dL could mean you have diabetes, as well.


According to the American Diabetes Association, symptoms of high glucose levels include frequent urination, extreme hunger and thirst, extreme fatigue and irritability, unusual weight loss, frequent infections, blurred vision, tingling and numbness in the hands and feet, cuts and bruises that take a long time to heal, and recurring bladder, gum or skin infections. It is possible for you to have high glucose levels with no symptoms, so be sure to have your doctor check your levels at your regular physical.

Dangers of Hyperglycemia

The danger of continuously high blood glucose or hyperglycemia is that sugar coats the red blood cells, causing them to become stiff and "sticky". These cells interfere with proper blood circulation and can cause buildup on blood vessels and organs. The small, fragile blood vessels of the eyes, feet and kidneys are the most vulnerable, and problems are usually first noticed in these areas. If hyperglycemia is not controlled, it can eventually lead to heart disease, stroke, kidney failure, vision loss, tooth loss, stroke, nerve damage and loss of limbs due to circulation problems.


Lifestyle changes and medications are usually prescribed to help lower blood glucose levels. Following a healthful eating plan will help you control your blood glucose and prevent you from developing further complications. Your diet should consist of vegetables, whole grains, fresh fruit, lean meats and dairy, legumes and seeds, with limited or no processed foods. Consult a diabetes expert or dietitian to help develop a plan that works for you.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.
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