Ana Maria Kausel, MD, is a double board-certified endocrinologist affiliated with Mount Sinai St. Luke's/Mount Sinai West in New York City.
Hyperglycemia (high blood sugar) is a condition that occurs when the glucose levels in your blood rise too high. Hyperglycemia is commonly a symptom and complication of diabetes.
Glucose can build up in the blood when the body doesn't produce enough insulin, a hormone that helps manage blood sugar by getting glucose into cells, or can’t use insulin properly. Blood glucose levels that are higher than 130 milligrams per deciliter (mg/dL) while fasting or higher than 180 mg/dL about two hours after a meal are typically considered hyperglycemia. Any tests higher than 200 mg/dL are also considered hyperglycemia.
Symptoms tend to come on slowly and may include frequent urination and increased thirst.
A combination of lifestyle factors, such as diet and exercise, and medications and insulin are often part of the treatment plan. Your doctor will take into consideration factors such as age, overall health, severity and frequency of high blood glucose levels, and even cognitive function (since self-management can be complicated) when creating an individualized treatment plan.
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. For those with type 2 diabetes, the body becomes resistant to insulin or doesn't produce enough of it. Causes in those without diabetes can include hormone fluctuations or a rise in stress hormones.
For hyperglycemia to cause symptoms, blood glucose levels must reach significantly high levels. When symptoms do develop, they typically come on slowly over several days or weeks and may include excessive thirst, increased hunger, frequent urination, fatigue, and blurry vision. More severe symptoms can include nausea and vomiting, fruity breath, rapid breathing, or loss of consciousness.
Carbohydrates are nutrients that break down into glucose in the body. They can include sugar, starches, and fiber. Those with diabetes need to monitor their carbohydrate intake. Simple carbohydrates (table sugar, fruit, milk) are digested rapidly into glucose and complex carbohydrates (whole grains, vegetables) are digested more slowly for a more steady rise in blood sugar.
A surge in daily hormones that occurs between 4 a.m. and 5 a.m. that can lead to elevated blood sugar levels in the morning. Everyone gets this surge, but people with diabetes may have an inadequate insulin response to adjust for it.
A serious condition that is a combination of hyperglycemia, elevated ketones, and metabolic acidosis. DKA can lead to a diabetic coma or death. It begins when hyperglycemia goes untreated and your body doesn’t have enough insulin. As your cells don’t receive adequate glucose, your body burns fat and produces ketones. High levels of ketones can make the blood acidic and become poisonous.
Glucose is the main sugar in the blood that’s a major source of fuel for the body’s cells. Those with diabetes can help manage blood glucose levels by adjusting their diet and food choices. The hormone insulin helps control levels in the blood. If blood sugar is too high or too low it can lead to serious medical problems.
Insulin is a hormone made by the pancreas that helps to manage glucose in the blood. In those with type 1 diabetes, the pancreas stops producing insulin and supplemental insulin is essential. In those with type 2 diabetes, insulin can be lower than normal and/or the body is no longer able to use insulin efficiently (insulin resistance), and medications or supplemental insulin may be needed.
Explore an interactive model below that shows an up-close view inside a human liver cell, and how hyperglycemia can occur when glucose and insulin do not properly bind.
American Diabetes Association. 6. Glycemic Targets: Standards of Medical Care in Diabetes-2020. Diabetes Care. 2020;43(Suppl 1):S66-S76. doi:10.2337/dc20-S006
American Heart Association. Carbohydrates. Updated April 16, 2018.
Monnier L, Colette C, Dejager S, Owens D. Magnitude of the dawn phenomenon and its impact on the overall glucose exposure in type 2 diabetes: is this of concern? Diabetes Care. 2013;36(12):4057–4062. doi:10.2337/dc12-2127
U.S. Centers for Disease Control and Prevention. Insulin resistance and diabetes. Updated August 12, 2019.