What Is Hyperglycemia (High Blood Glucose)?

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Glucose can build up in the blood when the body doesn't produce enough insulin, a hormone that acts as a sort of key to unlocking cells so glucose can get inside them.

The medical term for this is called hyperglycemia (high blood glucose) and refers to higher than normal levels of glucose (sugar) in the blood—above 200 milligrams per deciliter (mg/dl).

For otherwise healthy adults, a normal blood sugar range is between 90 and 180 mg/dL.

Hyperglycemia is a symptom of both type 1 diabetes and of type 2 diabetes. In other words, it's one of the factors that cause a person to be diagnosed with either condition. It is also a complication of the two forms of diabetes. This means that once a diagnosis is made and a person has begun to successfully manage their diabetes (i.e., they've lowered their blood sugar to a normal level and can maintain it) hyperglycemia can be a sign that there's actually a problem with the treatment protocol or another external factor.

Other conditions can also be associated with elevated blood sugar levels. But, regardless of what might cause hyperglycemia, the symptoms essentially will be the same. If blood glucose isn't treated and controlled, the consequences can be serious.

Illustrated human body with arrows outlining common symptoms of hyperglycemia. Text on image reads: Hyperglycemia: Common Symptoms: fatigue; blurry vision; excessive thirst; fruity breath; increased hunger; nausea and vomiting; increased urination.
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Hyperglycemia Symptoms

For hyperglycemia to cause obvious symptoms, blood glucose levels must reach significantly high levels. This takes time. So, when symptoms do develop, they come on very slowly over several days or weeks, becoming increasingly more serious thereafter. Some people who've had type 2 diabetes for a long period may not ever develop symptoms from elevated blood sugar levels.

Common symptoms of hyperglycemia include:

  • Excessive thirst (polydipsia)
  • Increased hunger (polyphagia)
  • The need to urinate more frequently than usual (polyuria)
  • Blurred vision
  • Feeling tired and weak

When blood sugar levels become extremely high or stay high for a long time, more severe symptoms can develop. These are often considered an emergency:

  • Stomach pain
  • Weight loss
  • Nausea and vomiting
  • A fruity scent on the breath
  • Deep, rapid breathing
  • Loss of consciousness

Rare symptoms of hyperglycemia include: 

  • Numbness in the hands, feet, or legs due to nerve damage
  • Skin problems, including dry, itchy skin, slow-healing wounds, and patches of thick, velvet-textured skin in folds are creases (such as the neck) called acanthosis nigricans
  • Frequent yeast infections (in women)
  • Erectile dysfunction (in men)
  • Extreme thirst, confusion, high fever, and weakness or paralysis on one side of the body (signs of hyperglycemic hyperosmolar nonketotic syndrome, which may lead to a coma and even death)
  • Diabetic ketoacidosis (DKA): An extremely serious condition most common in type 1 diabetes that develops when the body has little or no insulin

Among the complications of hyperglycemia are vascular problems that can lead to eye damage (retinopathy), kidney problems (nephropathy), and peripheral and autonomic neuropathy (nerve loss in the feet or other parts of the body).

Persistent high glucose levels can also lead to heart disease or peripheral arterial disease.

During pregnancy, gestational diabetes that results from elevated blood sugar levels can be devastating. Complications range from preeclampsia (uncontrolled blood pressure in the mother) to high birth weight or low glucose levels in the baby to miscarriage. Babies born to moms with diabetes are at risk of problems such as obesity, type 2 diabetes, and ketoacidosis as they grow into childhood.

Causes

Problems with the pancreas and/or insulin production can cause blood sugar levels to rise to unhealthy levels.

For people with type 1 diabetes, the pancreas isn't able to produce enough insulin. In the case of type 2 diabetes, the body becomes resistant to insulin or doesn't produce enough of it.

Insulin helps transport glucose from the bloodstream with the help of glucose transporters.

Genetics can play a role in either type of diabetes, but family history is more important in type 2 than type 1.

For someone to develop type 2 diabetes, they first must have a predisposition to the illness that makes them susceptible to actually developing the condition in the presence of certain risk factors.

These include being overweight or obese, not getting enough physical activity, and smoking.

Gestational diabetes, an extreme increase in glucose during pregnancy, is "caused by the hormonal changes of pregnancy along with genetic and lifestyle factors," according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Women who are overweight or obese when they become pregnant or have a family history of diabetes are particularly at risk of gestational diabetes. 

It's possible to have hyperglycemia without having diabetes, too. For example, hormone fluctuations during the day can lead to unexpected increases in blood sugar. Also, the release of certain stress hormones in response to tissue damage sometimes leads to an increase in blood sugar levels. This is known as hyperglycemia without diabetes or stress-induced hyperglycemia (SIH). 

Diagnosis

The only way to tell if glucose levels are higher than normal is by testing blood.

People with diabetes usually check their blood sugar levels several times throughout the day—first thing in the morning, two hours after a meal, and before bed. This way they can make sure their levels are staying within ranges set for them by their doctor based on factors such as age, weight, and activity level.

There are also several types of clinical tests for measuring glucose levels. Some are used to diagnose not only hyperglycemia but also prediabetes and diabetes, including:

  • Fasting plasma glucose (FPG) or fasting blood glucose Test (FBG): This test measures glucose levels in the blood after eight hours of not eating or drinking anything besides water. It is usually done first thing in the morning, before breakfast. It's used to diagnose diabetes and impaired glucose tolerance, and can help people with diabetes detect hyperglycemia.
  • Hemoglobin A1C test: This test, which looks at average levels of blood glucose over a span of three months, is used to diagnose prediabetes and type 2 diabetes. It can also help someone with diabetes manage their blood sugar levels. 
  • Fructosamine test: Like the A1C test, this test determines blood glucose levels over a span of two or three weeks. It can help monitor changes in treatment or medication and is also the test used for gestational diabetes. 
  • Oral glucose tolerance test (OGTT): Also called the glucose tolerance test, the OGTT looks at how well the body is able to metabolize glucose. The test involves testing blood before and two hours after drinking an intensely sweet beverage.

Treatment

When creating a plan to treat hyperglycemia, a doctor will take into consideration factors such as age, overall health, severity and frequency of high glucose levels, and even cognitive function (since self-management can be complicated). 

It's important that a person who has been newly diagnosed with diabetes receives a diabetes self-management education (DSME). This also could be helpful for someone whose glucose levels are at high enough levels to put them at risk of diabetes. Discuss this as part of your treatment plan with your doctor.

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The lifestyle changes outlined in DSME include:

  • Dietary changes to lower the intake of carbohydrates: Eating more fiber can be helpful in controlling blood sugar levels as well.
  • Exercise: Activity burns glucose, which, in turn, decreases the amount of it in the blood.
  • Weight loss: Dropping extra pounds improves insulin sensitivity. 
  • Giving up cigarettes: Smoking is associated with hyperglycemia and the development of type 2 diabetes.
  • Blood sugar monitoring: This can help with evaluating how well someone is responding to therapy and managing high blood sugar. 
  • Cinnamon: There's preliminary research to suggest this spice might help lower blood sugar, so it can't hurt to flavor your morning coffee or oatmeal with a sprinkle or two.
  • Apple cider vinegar: In one small study, healthy people who drank a certain brand of apple cider vinegar had a significant decrease in fasting blood sugar. 

Although there are no over-the-counter treatments for hyperglycemia, there are several prescription medications for keeping blood sugar at healthy levels, including:

  • Insulin: People with type 1 diabetes usually need multiple doses of insulin each day because their bodies don't produce the hormone naturally. People with type 2 diabetes who have severely elevated blood sugar levels may also need insulin therapy. 
  • Symlin Pen (pramlintide): This medication is used in people whose diabetes cannot be managed with insulin. It's an injection used at mealtimes along with insulin. 
  • Oral medications: These may be prescribed based on a person's age, gender, weight, and other factors. A common drug for dealing with hyperglycemia is metformin, which is available under several brand names including Fortamet and Glucophage. 

May 28, 2020: The FDA has requested that manufacturers of certain formulations of metformin voluntarily withdraw the product from the market after the agency identified unacceptable levels of N-Nitrosodimethylamine (NDMA). Patients should continue taking their metformin as prescribed until their health professional is able to prescribe an alternative treatment, if applicable. Stopping metformin without a replacement can pose serious health risks to patients with type 2 diabetes.

A Word From Verywell

The easiest way to treat hyperglycemia is to prevent it. This includes taking the necessary steps to lower your blood sugar, exercising regularly, keeping to the eating plan suggested by your healthcare team, and taking your medications as directed. 

It also is important to routinely monitor your blood. In the event of hyperglycemia, you can either make adjustments to your insulin prescription or supplement with an extra dose.

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