Hyperglycemia: Symptoms, Causes, Management

Managing blood sugar levels with diabetes can be like walking on a balance beam.

If blood sugars are too low (hypoglycemia), it’s cause for concern and can cause unwanted side effects.

If blood sugars are too high (hyperglycemia) for an extended period, it can cause damage to the body and cause complications.

The ultimate goal when treating diabetes is to achieve more steady, balanced blood sugars while avoiding extreme highs and lows

High blood sugar is something that should be avoided due to its adverse impacts on our health.

Understanding what high blood sugar is, what causes it, its symptoms, and treatment are all critical in preventing hyperglycemia.

What is hyperglycemia?

Hyperglycemia is the term for high blood glucose (sugar) levels. While having sugar in our blood is necessary for survival, having too much blood sugar is unhealthy and can lead to health problems.

Blood sugar is measured in milligrams per deciliter, or mg/dL. The definition of high blood sugar depends on what time the blood sugar reading is measured.

For people without diabetes, blood sugar levels are considered high when they are:

  • Greater than 100 mg/dL when fasting (no eating or drinking anything besides water) for at least eight hours

  • Greater than 140 mg/dL within 2 hours of starting a meal

When someone has diabetes, the blood sugar targets are as follows, according to the American Diabetes Association:

  • Between 80-130 mg/dL before meals

  • Less than 180 mg/dL 1-2 hours after starting a meal

Blood sugar targets in diabetes are more strict per the American Association of Clinical Endocrinologists (AACE):

  • Less than 110 mg/dL fasting

  • Less than 140 mg/dL two hours after a meal

A hemoglobin A1c test measures the average blood sugar over the past 2-3 months in the form of a percentage. A normal A1c is below 5.7%; borderline high is between 5.7%-6.4%, and diabetes is diagnosed when the A1c is 6.5% and higher.

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Symptoms of hyperglycemia

When someone has borderline high blood sugar, such as prediabetes, there usually aren’t any symptoms.

This is why getting screened for blood sugar problems regularly, starting at age 45 (earlier for people with multiple risk factors), is so important.

Some of the early signs of hyperglycemia that may tip someone off enough to go visit with their doctor include:

  • Unintentional weight loss: The body isn’t able to use glucose as energy when it’s high in the bloodstream. Glucose needs to move from the blood to our cells with the help of insulin to be used as fuel. When our cells are starved of fuel, weight loss can occur as our body breaks down muscles for alternative fuel. Weight loss can also be a result of dehydration from uncontrolled blood sugar.

  • Increased urination: The body tries to rid itself of some of the high blood sugar by excreting it in the urine. People with high blood sugar often experience increased urination as the body rids itself of sugar while pulling fluids with it. This is why some healthcare providers order urine glucose tests to diagnose blood sugar problems; a normal test result would show no glucose in the urine.

  • Increased thirst: Increased urination can be dehydrating, which can cause an increased thirst sensation.

  • Increased hunger: When the food we eat isn’t able to be converted into usable energy, it can cause hunger due to the cells starving from lack of fuel.

  • Fatigue: When the body isn’t able to use glucose as energy due to high blood sugar, it can result in a noticeable decline in energy levels.

For chronic hyperglycemia, more symptoms can occur, such as:

  • Poor wound healing: High blood sugar delays wound healing, which is one of the many reasons long-term diabetes can increase the risk of wounds requiring amputation.

  • Numbness and tingling of the hands and feet: Prolonged periods of high blood sugar can cause nerve damage. One of the more well-known types of nerve damage, peripheral neuropathy, can cause numbness or tingling in the hands and feet and spreading to the arms and legs. Those with neuropathy may not feel a wound on their feet, which can lead to diabetic foot ulcers.

  • Increased infections: High blood sugar interferes with the immune system, which can increase susceptibility to illness and infection.

What causes hyperglycemia?

The leading cause of hyperglycemia is the disease of diabetes mellitus. Diabetes is classified as type 1 or type 2, with type 2 being the most prevalent type. Type 1 diabetes, also considered juvenile-onset diabetes, is often diagnosed before age 18.

Type 1 diabetes is an autoimmune disorder where the body attacks the cells of the pancreas responsible for producing the hormone insulin. Without insulin, sugar isn’t able to be transferred from the bloodstream to cells.

People with type 1 diabetes must inject insulin several times per day to manage their blood sugar levels. The risk factors for type 1 diabetes tend to be more genetic and environmental than lifestyle-related.

Type 2 diabetes is the most prevalent form of diabetes. According to the Center for Disease Control, 90-95% of people with diabetes in America have type 2.

Type 2 diabetes occurs when the body doesn’t respond to insulin well, or it doesn’t produce enough insulin.

The risk factors for type 2 diabetes are more well-established than those for type 1 and include age, body stature, race, and family history.

Signs of insulin resistance, which can occur even in children, include:

  • Patches of dark, velvety skin called acanthosis nigricans

  • Waistline greater than 40 inches in men and greater than 35 inches in women

  • Fasting blood sugar greater than 100 mg/dL

  • Blood pressure readings greater than 130/80

  • Fasting triglyceride level greater than 150 mg/dL

  • HDL (good cholesterol) less than 40 mg/dL in men and less than50 mg/dL in women

Prediabetes is a condition where blood sugars are considered high, but not high enough to be diagnosed as diabetes. Having prediabetes is a significant risk factor for developing type 2 diabetes later on.

Certain medications can cause acute high blood sugar, even in people without diabetes. Steroids are one of the most well-known medications that increase blood sugar. People who take steroids consistently for a long period of time are more likely to experience insulin resistance and blood sugar issues.

Illness and stress can also increase blood sugar in people with and without diabetes. When the body is under stress, certain hormones have released that trigger the body to increase blood sugar.

People who are hospitalized or have undergone major surgery can have temporarily increased blood sugar levels until their illness or injury resolves.

Complications of hyperglycemia

Normally, the body regulates blood sugar very well, and blood sugars are rarely high for a long period of time, if ever. The pancreas secretes a small amount of insulin throughout the day and releases more elevated amounts of insulin in response to eating.

Whether it’s due to illness, stress, or the more common cause of diabetes, this balanced system is disrupted, leading to high blood sugar.

In type 1 diabetes, untreated hyperglycemia can lead to a life-threatening condition called diabetic ketoacidosis (DKA).

DKA occurs when insulin levels are very low, which causes the body to start producing ketones to use as fuel instead of glucose. A sign of ketone bodies being present is fruity-smelling breath. Other symptoms of DKA include:

The “type 2 version” of DKA is called hyperglycemic hyperosmolar syndrome (HHS). HHS doesn’t cause ketones (nonketotic) to build up, but it does present as:

  • Very high blood sugar

  • Dehydration

  • Decreased alertness

Chronic hyperglycemia, such as in the case of diabetes, can cause numerous adverse health outcomes. Keeping blood sugar levels controlled is the best way to avoid complications such as:

  • Heart disease: High blood sugar causes hardening of the arteries called atherosclerosis, which is a risk factor for developing cardiovascular disease (heart disease). If an artery becomes too narrow, it can become blocked, which results in a heart attack (myocardial infarction) or stroke, depending on where the blockage occurs.

    Diabetes and insulin resistance is also linked with dyslipidemia or abnormal cholesterol levels. Having high levels of LDL (bad) cholesterol and low levels of HDL (good) cholesterol increase the risk of heart disease.

    People with diabetes are also more likely to have high blood pressure, which is another risk factor for heart disease.

  • Kidney problems: High blood sugar damages the vessels in the kidneys, which are responsible for removing waste from our blood and help to control blood pressure. If diabetes isn’t controlled, chronic kidney disease is more likely to occur. Chronic kidney disease can progress to the point of needing dialysis or a kidney transplant.

  • Neuropathy and retinopathy: High blood sugar can cause nerve damage, known as neuropathy. Many people experience this in the form of peripheral neuropathy. Peripheral neuropathy causes pain as well as numbness and tingling of the extremities.

    Diabetes can also damage the blood vessels in the eyes, which leads to retinopathy. Retinopathy can potentially lead to loss of vision.

  • Wound healing problems: High blood sugar impairs the body’s ability to heal itself. When wounds don’t heal quickly, there is a higher chance of infection. The chances of wound complications are even higher if the person also has neuropathy because they can’t feel the wound, and it may go untreated for a long time.

    If limbs are severely damaged from a poorly healing wound, it may need to be amputated. Diabetes is thought to be the leading cause of leg amputations worldwide.

Prevention of hyperglycemia

While some risk factors for developing hyperglycemia can’t be avoided, such as having a family history of diabetes, some things can be done to lower the risk of developing high blood sugar.

Have your blood sugar screened regularly if you have risk factors for diabetes, you should get your blood sugar screened every three years. Some risk factors for type 2 diabetes include:

  • Inactivity

  • Family history

  • Race (African Americans, Hispanics, Native Americans, and Asian Americans are at higher risk)

  • Being 45 years or older

  • High blood pressure

  • Low HDL (good cholesterol) levels and/or high blood triglycerides

Be physically active. Getting 30 minutes or more of moderate to vigorous physical activity most days of the week helps lower the likelihood of insulin resistance. Strength and resistance training is also beneficial for reducing insulin resistance.

Eat a balanced diet. Eating foods rich in fiber such as fruits, vegetables, whole grains, legumes, nuts, seeds, and lean protein sources such as chicken and fish can help promote overall health. A diet high in refined sugar, such as sugary drinks and sweets, can worsen insulin resistance and cause further blood sugar problems in someone predisposed to having high blood sugar.

Ask your doctor about diabetes medication alternatives. If you’re prescribed a steroid for long-term use, have a discussion with your doctor about the risks and potential alternatives. Steroids raise blood sugar, and over time, can result in steroid-induced diabetes.

Treatment of hyperglycemia

Depending on the cause and duration of hyperglycemia, treatments can include changing medications, lifestyle modifications, or starting diabetes medications such as insulin.

For borderline hyperglycemia, such as prediabetes, lifestyle modifications are often the recommended course of action.

Being physically active, eating foods that promote stable blood sugar levels (such as the plate method), and practicing good sleep hygiene are good lifestyle modifications to help improve hyperglycemia.

There are many medications available for the treatment of diabetes. Insulin is typically the only medication used for type 1 diabetes and is often used to treat type 2 diabetes, as well.

Insulin therapy comes in several forms, including long-lasting/ basal insulin, intermediate-acting, and short-acting/mealtime.

There are several other treatment options available for use in type 2 diabetes. Some of the more popular medications include:

  • Metformin: Helps to reduce the amount of sugar released by the liver and improves insulin sensitivity

  • Sulfonylureas: Stimulate the pancreas to secrete more insulin

  • GLP1 receptor agonists: Promote insulin production, decrease glucose release from the liver and slows stomach emptying to increase satiety

  • DPP-4 inhibitors: Promote insulin production, decrease glucagon (a hormone that increases blood sugar) production, and delays gastric emptying.


Hyperglycemia is the term for high blood sugar. Hyperglycemia can be acute, or short-lasting, such as in the case of illness and stress.

Chronic hyperglycemia, or having high blood sugar for a longer period of time, is the main symptom of diabetes. Chronic high blood sugar can cause numerous diabetes complications if left untreated.

Blood sugar is considered high in a person without diabetes when it’s greater than 100 mg/dL fasting or greater than 140 mg/dL within two hours of a meal.

For people with diabetes, blood sugar should ideally fall between 80-130 mg/dL before eating and be less than 180 mg/dL within 1-2 hours of a meal, according to the ADA.

Hyperglycemia can be prevented by having blood glucose screened often, especially for people at higher risk of developing diabetes. It can also be prevented through healthy lifestyle habits and the use of diabetes medications as needed.

There are many treatment options for those diagnosed with diabetes, including numerous medications. Healthy lifestyle habits and blood glucose monitoring can also help people with diabetes to control their blood sugars.

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  2. https://www.diabetes.org/diabetes/medication-management/blood-glucose-testing-and-control/hyperglycemia
  3. Mouri MI, Badireddy M. Hyperglycemia. [Updated 2019 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-.
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