Hyperglycaemia

Hyperglycaemia, also known as high blood sugar, occurs when the level of glucose in your blood rises above normal levels. This condition most commonly affects people with diabetes, but it can also develop in those without the disease, particularly during illness or hospitalization.

Table of contents

• What is hyperglycaemia?
• What causes hyperglycaemia?
• Signs and symptoms
• How is hyperglycaemia diagnosed?
• Complications and risks
• Treatment and management
• How to prevent hyperglycaemia

What is hyperglycaemia?

Hyperglycaemia is the medical term for blood glucose that is higher than normal. The word comes from Greek: “hyper” meaning high, “glykys” meaning sweet or sugar, and “haima” meaning blood^[1].

When you eat food, especially carbohydrates, your body breaks it down into glucose, a type of sugar that is the main source of energy for all cells in your body. Normally, your body uses a hormone (a chemical messenger) called insulin to move glucose from your blood into your cells. This process lowers the glucose in your blood and provides your cells with the energy they need to function^[2].

Hyperglycaemia occurs when the body does not produce enough insulin or cannot use insulin properly. In both cases, glucose stays in the blood instead of being sent to the cells, causing blood glucose levels to remain elevated^[3].

For people who have not been diagnosed with diabetes, hyperglycaemia is typically defined as blood glucose greater than 125 mg/dL (milligrams per deciliter) while fasting, which means not eating for at least eight hours. A blood glucose level between 100 mg/dL and 125 mg/dL while fasting indicates impaired glucose tolerance, also called pre-diabetes^[4].

For people with diabetes, hyperglycaemia is usually considered to be a blood glucose level greater than 180 mg/dL one to two hours after eating, though this can vary depending on individual target levels set with a healthcare provider^[5].

What causes hyperglycaemia?

Many factors can cause blood sugar levels to rise too high. For people with diabetes, several common triggers include not taking enough medication, eating more carbohydrates than planned, exercising less than usual, or experiencing stress from illness or emotional situations^[6].

If you have type 1 diabetes, your body does not make enough insulin. In type 2 diabetes, your body makes insulin, but your cells do not respond to it properly, a condition called insulin resistance^[7].

Hyperglycaemia can also occur in people who do not have diabetes. When someone is sick, the body produces extra amounts of stress hormones, such as cortisol, glucagon, growth hormone, and epinephrine. These hormones help the body handle the stress of illness by making extra glucose to fuel increased energy needs. However, these extra hormones can sometimes cause insulin resistance, preventing insulin from doing its job. As a result, glucose builds up in the blood^[8].

Other causes of hyperglycaemia include certain medications such as corticosteroids, thiazide diuretics, beta-blockers, and antipsychotics. Medical conditions that affect the pancreas, which produces insulin, can also lead to high blood sugar. Conditions that cause insulin resistance, such as Cushing’s syndrome and acromegaly, may contribute to hyperglycaemia as well. Pregnancy and emotional stress are additional factors^[9].

Gestational diabetes, which occurs during pregnancy, is another cause of hyperglycaemia. It affects about 4% of all pregnancies and is primarily due to decreased insulin sensitivity during pregnancy^[10].

Signs and symptoms

Hyperglycaemia usually does not cause symptoms until blood sugar levels are quite high, typically above 180 to 200 mg/dL (10 to 11.1 mmol/L). Symptoms develop slowly over several days or weeks. The longer blood sugar levels stay high, the more serious symptoms may become^[11].

Early signs and symptoms of hyperglycaemia include feeling very thirsty, needing to urinate frequently (especially at night), feeling more tired than usual, having blurred vision, experiencing headaches, and feeling weak or unusually tired^[12].

If hyperglycaemia is not treated, it can lead to a serious condition called diabetic ketoacidosis (DKA), especially in people with type 1 diabetes. This occurs when the body cannot access glucose for energy and instead breaks down fat for fuel. This process produces toxic acids called ketones, which build up in the blood and urine^[13].

Symptoms of diabetic ketoacidosis include fruity-smelling breath, dry mouth, abdominal pain, nausea and vomiting, shortness of breath, confusion, and loss of consciousness. This is a medical emergency that requires immediate treatment^[14].

In people with type 2 diabetes, very high blood glucose levels can lead to another life-threatening condition called hyperosmolar hyperglycemic state (HHS), which causes profound dehydration and changes in mental status^[15].

How is hyperglycaemia diagnosed?

If you have diabetes, you will most likely need to check your blood glucose every day to make sure it is not too high. You can do this with a blood glucose meter or a continuous glucose monitoring (CGM) system. A blood glucose meter measures the amount of sugar in a small sample of blood, usually from your fingertip. A CGM uses a sensor inserted under the skin to measure your blood sugar every few minutes^[16].

Healthcare providers can also use blood tests to check if your blood glucose is too high. For people with diabetes, target blood sugar levels before meals are typically between 80 and 130 mg/dL, and less than 180 mg/dL two hours after meals. However, your target blood sugar range may differ depending on your age, other health problems, and individual circumstances^[17].

If your blood sugar level is 240 mg/dL (13.3 mmol/L) or above, you should use an over-the-counter urine ketones test kit to check for ketones. If the urine test is positive, your body may have started making the changes that can lead to diabetic ketoacidosis, and you should contact your healthcare provider immediately^[18].

Complications and risks

If hyperglycaemia is not treated, it can cause serious health problems. Long-term hyperglycaemia can lead to complications that affect many parts of the body, including damage to the eyes, kidneys, nerves, heart, and peripheral vascular system^[19].

When blood glucose levels are very high, especially above 15 mmol/L, or when hyperglycaemia lasts for extended periods, it can cause damage to blood vessels, tissues, and organs throughout the body^[20].

Acute complications of severe hyperglycaemia include diabetic ketoacidosis and hyperosmolar hyperglycemic state, both of which are life-threatening conditions requiring immediate medical attention^[21].

People with hyperglycaemia also have a greater risk for infections, such as urinary tract infections, pneumonia, and skin infections like thrush. This is because high blood sugar levels create an environment where bacteria and yeast can grow more easily, and because diabetes lowers the body’s ability to fight infection^[22].

Treatment and management

The main goals in treating hyperglycaemia are to bring blood sugar levels back to the target range and to treat any underlying causes. If you have hyperglycaemia, it is important to act quickly to prevent serious complications^[23].

Insulin is the most important treatment for controlling hyperglycaemia, especially in people who are critically ill or hospitalized. For people with type 1 diabetes, insulin is always necessary. People with type 2 diabetes may need insulin as well, depending on the severity of their hyperglycaemia^[24].

If your blood sugar level is high, usually above 13 mmol/L or 14 mmol/L, you should check for ketones. If ketones are present, you may need to increase your dose of insulin or give yourself an extra dose. You should also try to drink plenty of water and other sugar-free fluids to prevent dehydration^[25].

For people with diabetes who have mild to moderate hyperglycaemia, treatment may include adjusting your diabetes meal plan, increasing physical activity, or changing your diabetes medications. Your healthcare team may need to adjust your treatment plan based on your individual needs^[26].

If your high blood sugar does not go down with self-care at home, or if you cannot keep fluids down, you should see your doctor immediately or go to your nearest emergency department. If you have symptoms of diabetic ketoacidosis, such as fruity-smelling breath, nausea and vomiting, abdominal pain, shortness of breath, or confusion, call emergency services immediately^[27].

How to prevent hyperglycaemia

The best way to prevent hyperglycaemia is to follow your diabetes management plan carefully. This includes checking your blood sugar regularly, taking your medications as prescribed, following a healthy eating plan, and staying physically active^[28].

Understanding how different foods affect your blood sugar is important. Learning about carbohydrate counting and meal planning can help you make better food choices. It is helpful to know that carbohydrates often have the biggest impact on blood sugar levels because the body breaks them down into sugar^[29].

Regular physical activity helps your body use insulin more effectively and can lower blood sugar levels. Exercise helps your muscles use blood sugar for energy. Even short sessions of activity, such as 10-minute exercise sessions three times a day, can be beneficial^[30].

Managing stress is also important, as stress can cause blood sugar to rise. Finding activities that help you relax, such as taking a walk, listening to music, or gardening, can help keep your blood sugar levels more stable^[31].

If you have diabetes, it is important to monitor your blood glucose levels regularly and keep them within your target range. If your blood sugar levels are regularly above 10 mmol/L, you should contact your diabetes team or healthcare provider for advice^[32].

When you are sick, your blood sugar levels are more likely to rise, so it is especially important to monitor them closely during illness. Follow any “sick day rules” discussed with your diabetes team, stay hydrated, and contact your healthcare provider if you are concerned^[33].