Medically Reviewed By William C. Lloyd III, MD, FACS

What is hyperglycemia?

Hyperglycemia is the medical term for abnormally high blood glucose or high blood sugar. It usually affects people who have diabetes. In general, hyperglycemia is a blood sugar level higher than 125 mg/dL when fasting or 180 mg/dL two hours after eating. If you have diabetes, your care team will give you specific goals for both a high blood sugar cut off and a low blood sugar one.

Glucose is the body’s main energy source. It comes from the foods you eat. Glucose levels in healthy individuals fluctuate within a normal range throughout the day. Several factors affect glucose levels, including eating and exercising. Glucose levels can also change with illnesses, infections and medications. Abnormally high glucose levels occur in people with diabetes because they do not have enough insulin or their cells cannot use insulin properly. Insulin is a hormone that moves glucose from the blood into the cells. Without insulin, excess glucose accumulates in the blood.

When you have diabetes, keeping your blood sugar level in the normal range is a balancing act. It depends on your activity level, carbohydrate intake, and taking your diabetes medicines as prescribed. Eating more, exercising less, or skipping or not using enough diabetes medicines can cause hyperglycemia. Unplanned emotional and physical stresses can also cause blood sugar levels to rise above normal.

The classic hyperglycemia symptoms include increased thirst, urination and hunger, along with fatigue and vision problems. These symptoms usually begin slowly and may not be noticeable until blood sugar levels have been high for a long time. Left untreated, persistent high blood sugar levels can damage the blood vessels, eyes, heart, kidneys and nerves. Severely high blood sugar levels can lead to life-threatening complications, such as ketoacidosis and diabetic coma.

Treating hyperglycemia involves medicines to bring blood sugar levels back to the normal range. When hyperglycemia is severe, this requires hospital treatment to safely lower blood glucose. If you have diabetes, seek immediate medical care for sustained glucose levels higher than 240 mg/dL, ketones in your urine, or vomiting that prevents you from keeping down food or fluids.

What are the symptoms of hyperglycemia?

Hyperglycemia symptoms tend to start gradually, sometimes over weeks. The longer blood sugar stays high and the higher the level goes, the more noticeable symptoms become. However, people who have had diabetes for a long time may have trouble recognizing the symptoms.

Common symptoms of hyperglycemia

Although symptoms can vary, the most common ones include:

  • Blurred vision

  • Constant hunger

  • Fatigue, weakness, or weight loss

  • Headache

  • Increased thirst and urination

  • Skin or vaginal infections and slow-healing wounds or sores

Checking your blood sugar will reveal a higher-than-normal result. If you get hyperglycemia often, make an appointment with your diabetes doctor. It may be necessary to adjust your treatment regimen.

Serious symptoms that might indicate a life-threatening condition

In some cases, hyperglycemia can be life-threatening. Seek immediate medical care (call 911) for potentially serious symptoms including:

These symptoms can be warning signs of ketoacidosis. This occurs when toxic ketones build up in the blood. Left untreated, ketoacidosis can be fatal.

What causes hyperglycemia?

Hyperglycemia occurs when there is an imbalance between glucose production and glucose uptake and use. Your body makes glucose when it breaks down carbohydrates you eat into various sugars. Your intestines absorb glucose into your bloodstream.

As the blood glucose level rises, the body directs the pancreas to release insulin. Insulin is responsible for moving glucose from the blood into the cells so they can use it for energy. As cells use insulin to take in glucose, blood levels of glucose fall.

In people with diabetes, either the pancreas does not make enough insulin or the cells cannot use insulin properly. This leads to glucose remaining in the circulating blood instead of going into the cells. The result is hyperglycemia.

Other hyperglycemia causes include:

What are the risk factors for hyperglycemia?

For people with diabetes, a number of factors increase the risk of developing hyperglycemia. Risk factors include:

  • Being less active than normal or not following your exercise plan

  • Eating more than you planned or not following your eating plan

  • Experiencing emotional or mental stress

  • Having an illness, infection or injury, including surgery

  • Skipping, not using enough, or having too low of a dose of diabetes medicine or insulin

  • Taking certain medicines, such as corticosteroids

If you have diabetes, talk with your doctor about factors that can trigger hyperglycemia. Ask how to manage specific situations, such as being sick, and how to adjust your treatment plan.

How do you prevent hyperglycemia?

If you have diabetes, there are steps you can take to reduce the risk of hyperglycemia and stay in your target glucose range. This includes:

  • Being active and exercising on a daily basis

  • Following your meal plan, including the timing and carbohydrate content of your meals and snacks

  • Limiting alcohol and not smoking

  • Maintaining a healthy body weight

  • Monitoring your blood sugar as directed by your doctor

  • Taking your medication or insulin as your doctor prescribes

Your diabetes care team is your main resource for managing your blood sugar. They can help you understand how to adjust your overall plan to accommodate changes in activity, meals, and other factors. Tell your team if you experience recurrent episodes of high blood sugar.

What are the diet and nutrition tips for hyperglycemia?

People with diabetes should eat a healthy, balanced diet. This includes lean proteins and meats, low-fat dairy, whole grains, and fresh fruits and vegetables. Eating complex carbohydrates will help maintain steady blood glucose levels. Limiting simple carbohydrates and sugary foods will help avoid wide swings in blood sugar.

Nutrition for people with diabetes also involves learning how much of different foods you can eat and how to balance food content with exercise. In general, no foods are completely off limits. It is a matter of knowing how much you can have and how often. Many people with diabetes use carbohydrate counting as a way to keep track of their food intake. A diabetes educator or registered dietitian is the best resource for learning this approach. These care team members can also teach you how to make last minute adjustments to your plan.

How do doctors diagnose hyperglycemia?

If you have diabetes, your doctor will set your upper and lower blood glucose level goals. The limit for hyperglycemia will vary with your age and will depend on whether or not you have eaten. Your doctor will let you know how often and when to check your blood sugar, or if you should use a CGM (continuous glucose monitor). Seeing your blood sugar level is the only way to know for sure if your glucose level is too high.

At appointments, your doctor can check your hemoglobin A1c level. An A1c test measures your long-term blood sugar control. It is an indicator of your average daily glucose levels over the last 2 to 3 months. A result higher than 7% generally means your blood sugar has been running higher than normal.

Your doctor may also perform a physical exam and ask several questions about your hyperglycemia symptoms including:

  • What symptoms are you having?

  • When did these symptoms start?

  • When do your symptoms occur? Are they continuous or do they come and go?

  • What, if anything, seems to make your symptoms better or worse?

  • What medical conditions do you have?

  • What medications do you take?

How do you treat hyperglycemia?

Hyperglycemia treatment involves medication to lower blood glucose levels. Doctors prescribe various oral medicines to accomplish this in people with type 2 diabetes. Insulin is necessary for people with type 1 diabetes and sometimes for people with type 2 diabetes.

When blood sugar levels are dangerously high, treatment in the hospital is necessary. Doctors use IV (intravenous) fluids, electrolytes and insulin to safely lower blood glucose to a normal range.

Home remedies for hyperglycemia

To manage high blood sugar levels at home, your doctor may recommend the following strategies:

  • Adjusting your insulin dose to treat a temporarily high glucose level

  • Eating smaller meal portions more frequently throughout the day

  • Getting physical activity to help your body use the extra glucose. Do not exercise if you have ketones in your urine, as this can make the situation worse.

  • Monitoring your blood sugar more often

  • Taking your oral medication as directed

Tell your doctor if you have high blood sugar levels frequently. It may be necessary to adjust the timing or dosage of your insulin or medication.

What are the potential complications of hyperglycemia?

Long-term hyperglycemia can lead to tissue damage and complications including:

People with chronically high blood sugar levels also have a higher risk of developing Alzheimer’s disease.

Hyperglycemia can also lead to life-threatening complications, including ketoacidosis and coma. Ketoacidosis occurs when you do not have enough insulin. Your body cannot use glucose for energy and starts using fat for energy instead. This produces toxic ketones, which can eventually cause coma and death.

The best way to protect yourself from the complications of hyperglycemia is to follow your treatment plan and choose healthy living habits.

Was this helpful?
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Aug 17
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