High Blood Sugar in People Without Diabetes

Several conditions and diseases can lead to high blood sugar

High blood sugar (hyperglycemia) is common in people with type 1 or type 2 diabetes, but it can also occur in people without these diseases as a result of a major illness, a chronic medical condition, a hormonal disorder, or certain medications. In that case, it is often called nondiabetic hyperglycemia.

Depending on the severity of the case, symptoms of high blood sugar in people who don't have diabetes include:

  • Headaches
  • Increased thirst or hunger
  • Frequent urination (peeing)
  • Severe fatigue
  • Blurred vision
  • Rapid heartbeats
  • Tingling, burning, or numbness in your hands or feet
  • Frequent infections or slow-healing sores
  • Unintended weight loss

This article describes eight common causes of nondiabetic hyperglycemia, as well as three factors that can independently increase your risk of getting high blood sugar.

High Blood Sugar Causes in People Without Diabetes - Illustration by Jessica Olah

Verywell / Jessica Olah

Defining Nondiabetic Hyperglycemia

Glucose is a type of sugar produced and stored by the liver which serves as the body's main source of energy. Once in circulation, 50% to 80% of glucose is used by the brain, kidneys, and red blood cells for fuel. The remaining is used to fuel energy units called mitochondria found in most cells.

The amount of glucose in the bloodstream is regulated by insulin, a hormone produced by the pancreas. After a meal, insulin will shut down the release of glucose from the liver to ensure levels don't get too high.

When any of these systems are impaired—including the different organs that regulate the pancreas—glucose can be released inappropriately and cause high blood sugar. It can also occur if liver cells become less responsive to the effects of insulin, known as insulin resistance.

Nondiabetic hyperglycemia may occur as a prelude to diabetes—such as with prediabetes (impaired glucose tolerance)—or it may have no relationship to diabetes whatsoever.

What Blood Sugar Level Is Considered High?

Blood sugar is considered high when levels are greater than 125 milligrams per deciliters (mg/dL) after fasting or greater than 180 mg/dL one to two hours after eating.


Common Causes of Nondiabetic Hyperglycemia

There are nine common causes of nondiabetic hyperglycemia that directly or indirectly disrupt the interaction between the pancreas (which produces insulin) and the liver (which produces glucose).

Cushing’s Syndrome

Cushing’s syndrome is a disorder caused by the excess secretion of adrenocorticotropic hormone (ACTH) produced by the pituitary gland. This, in turn, causes the adrenal glands to produce excessive amounts of cortisol, the body's main stress hormone.

When too much cortisol is released, it can counteract the effects of insulin and lead to insulin resistance. It can also decrease the amount of insulin released by the pancreas.

Pituitary adenomas, a typically benign tumor affecting the pituitary gland, are the cause of Cushing’s syndrome in more than 70% of cases. Prolonged use of steroid drugs like prednisone can also significantly increase the risk.

Approximately 10% to 30% of people with Cushing’s syndrome will develop impaired glucose tolerance, while 40% to 45% will develop diabetes.

Pancreatic Diseases

Pancreatic diseases such as pancreatitis, pancreatic cancer, and cystic fibrosis can cause hyperglycemia because pancreas cells are damaged in these conditions. Insulin is produced and released from the cells of the pancreas.

With inflammation and damage to the pancreas, pancreatic cells are no longer able to produce enough insulin to remove glucose from the blood to control blood sugar.

Polycystic Ovarian Syndrome

Polycystic ovary syndrome (PCOS) is a condition that causes irregular, often heavy menstrual periods. It is a common endocrine disorder among women of reproductive age. Women with PCOS have hormonal imbalances, such as increased levels of testosterone, insulin, and inflammatory proteins called cytokines released from fat tissue.

Despite increased levels of insulin, women with PCOS exhibit insulin resistance since their insulin hormones cannot adequately uptake glucose or utilize it for energy. Insulin receptors in women with PCOS cannot efficiently bind to insulin. Because insulin transports glucose, excess glucose remains in the bloodstream, producing hyperglycemia.

Trauma 

Physical stress to the body, including trauma, burns, and other injuries, can cause high blood sugar by altering the way glucose is metabolized.

Stress-induced hyperglycemia occurs when the body’s fight-or-flight response triggers the release of cortisol and another stress hormone known as epinephrine (adrenaline). Epinephrine increases the production of glucose, while glucose blocks the effects of insulin.

Physical stresses also cause the body to release inflammatory proteins known as cytokines that counteract insulin and lead to insulin resistance.

Surgery and Stress

Alterations to glucose metabolism that occur from physical stress to the body also occur after surgery. Surgery is a controlled form of stress to the body that results in similar increases in cytokines and hormones that drive the production of glucose in the liver and block the effects of insulin from removing excess glucose from the blood.

Up to 30% of patients can develop stress-induced hyperglycemia after surgery, with blood glucose levels that stay elevated long after returning home from the hospital. Elevated blood sugar after surgery can have significant effects on overall health and increases the risk of developing diabetes and other serious conditions.

Infections 

Stress-induced hyperglycemia can also result from the physical stress of having an infection, such as pneumonia or urinary tract infections. Increased levels of the stress hormone cortisol that occurs with infections block the ability of insulin to remove excess glucose from the bloodstream, keeping the body in a state of high blood sugar.

High blood glucose also results from infections as a normal reaction in order to support the needs of organs like the brain, kidneys, and red blood cells that depend on glucose for energy to aid in the immune system’s response to fight off an infection.

Medication Side Effects

Certain medications—such as catecholamine vasopressors like dopamine and norepinephrine, immunosuppressants like tacrolimus and cyclosporine, and corticosteroids—can increase blood glucose levels by activating enzymes that increase blood glucose levels and disrupting the release and activity of insulin to uptake glucose from the blood.

Hospitalized patients receiving nutrition through an IV may also be at an increased risk of developing hyperglycemia, as the nutritional fluid contains a sugar solution to help restore electrolyte balance. The concentration of this fluid should be carefully monitored in patients who are ill or recovering from surgery or injury in order to prevent further spikes in blood sugar.

Obesity

High blood sugar is associated with obesity since excess fat cells disrupt the balance of glucose and insulin. Excess fat cells called adipocytes release inflammatory proteins, such as interleukins and tumor necrosis factor, which increase the body’s resistance to insulin by activating processes that disrupt the body’s ability to produce and release insulin when blood sugar is high.

Excess fat cells also decrease the ability to remove glucose from the blood to be used for energy or stored as glycogen within skeletal muscles. With obesity, increased lipids, or fatty acid molecules, activate pathways that impair insulin signaling within muscles.

Genetics

A family history of diabetes can increase your risk of developing hyperglycemia. While diabetes can be prevented through diet and lifestyle factors, impaired insulin sensitivity can run in families and may make you more prone to developing high blood sugar.

Pregnant women can also develop gestational diabetes, often between 24 and 28 weeks of pregnancy, due to hormonal changes that affect the way that glucose is metabolized in the body. The influence of pregnancy hormones can interfere with the ability of insulin to remove excess glucose from the blood, causing blood sugar to stay elevated.

Lifestyle Risk Factors

Because we get glucose from foods we eat, diet factors in greatly into your risk of nondiabetic hyperglycemia. Similarly, because obesity is associated with an increased risk of glucose intolerance and insulin resistance, the lack of exercise can contribute because you are more likely to put on extra weight.

The Role of Diet

Diet plays a significant role in the development of high blood sugar. Excess consumption of sugar- and carbohydrate-containing foods raise blood sugar levels after eating as the food is broken down into glucose molecules that enter the bloodstream.

In a healthy person, the presence of more glucose molecules in the blood signals the pancreas to release insulin, which helps uptake glucose from the blood and transports it to the muscles and liver to be used for energy and storage. As blood sugar decreases, the signals to the pancreas to release more insulin stop, and blood sugar levels should return to a stable baseline.

When levels of blood sugar continually become elevated with repeat and excessive sugar and carbohydrate consumption, the excess glucose in the bloodstream stimulates the pancreas to release a lot of insulin. Over time, the body stops responding to insulin due to chronic high blood sugar, causing insulin resistance and keeping blood sugar high.

Managing a healthy and balanced diet with proteins, fats, and fiber-rich foods while limiting sugar and processed and refined carbohydrates can help control blood sugar levels.

Excess alcohol consumption can also affect your blood sugar by interfering with your liver’s ability to regulate the production and release of glucose and negatively impact your body’s response to insulin.

The Lack of Physical Activity

Lack of physical activity can increase your blood sugar, as skeletal muscles are a main part of the body that uses glucose for energy or stores extra glucose for later use. With low levels of physical activity, the muscles become inactive and do not remove glucose efficiently from the blood.

Regular exercise can help lower blood sugar levels by increasing the need for muscles to remove glucose from the blood to use for energy.

A Word From Verywell

High blood sugar can result from a variety of causes, not just diabetes. You do not have to live with diabetes to develop hyperglycemia. Having high blood sugar can increase your risk of developing diabetes and related complications later on. 

A variety of factors can contribute to high blood sugar, and some of them like diet and exercise can help keep your blood glucose in check. Sometimes high blood sugar in people without diabetes could be due to prediabetes, which could lead to the development of diabetes. If you have high blood sugar often, it’s important to check with your healthcare provider and monitor it.

Frequently Asked Questions

  • Can dehydration cause high blood sugar?

    Yes, dehydration can lead to transient increases in blood sugar. Less water in your body means that sugar in your blood is more concentrated.

  • Do you feel different if your blood sugar is high?

    Some people with hyperglycemia may have few symptoms or may not realize that symptoms like sudden fatigue are caused by high blood sugar. When blood sugar levels are excessive, people may feel anxiety due to rapid heartbeats, have trouble concentrating, or be confused.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Kristen Gasnick, PT, DPT
Kristen Gasnick, PT, DPT, is a medical writer and a physical therapist at Holy Name Medical Center in New Jersey.