Hyperglycemia means high blood sugar or glucose. Glucose comes from the foods you eat. Insulin is a hormone that moves glucose into your cells to give them energy. Hyperglycemia happens when your body doesn't make enough insulin or can't use it the right way.

People with diabetes can get hyperglycemia from not eating the right foods or not taking medicines correctly. Other problems that can raise blood sugar include infections, certain medicines, hormone imbalances, or severe illnesses.

If you have type 1 diabetes, avoid vigorous physical activity when you have ketones in your blood or urine. Ketones are chemicals your body might make when your blood glucose level is too high, a condition called hyperglycemia, and your insulin level is too low. If you are physically active when you have ketones in your blood or urine, your blood glucose level may go even higher. Ask your health care team what level of ketones are dangerous for you and how to test for them. Ketones are uncommon in people with type 2 diabetes.

High blood sugar is also called hyperglycemia (pronounced hye-per-gly-see-mee-uh). It means that your blood sugar level is higher than your target level or over 180. Having high blood sugar levels over time can lead to long-term, serious health problems.

If you feel very tired, thirsty, have blurry vision, or need to pee more often, your blood sugar may be high.

Check your blood sugar and see if it is above your target level or over 180. If it is too high, one way to lower it is to drink a large glass of water and exercise by taking a brisk walk. Call your health care team if your blood sugar is high more than 3 times in 2 weeks and you don’t know why.

Doctors call high blood glucose hyperglycemia.

Symptoms that your blood glucose levels may be too high include

• feeling thirsty
• feeling tired or weak
• headaches
• urinating often
• blurred vision

If you often have high blood glucose levels or symptoms of high blood glucose, talk with your health care team. You may need a change in your diabetes meal plan, physical activity plan, or medicines.

More than 795,000 people in the United States suffer from strokes annually, and an estimated 40 percent of people with acute ischemic stroke also have high blood sugar, or hyperglycemia. Although hyperglycemia is known to be associated with worse recovery for individuals with stroke, it is unclear if treatment interventions intended to bring blood sugar to normal levels can improve recovery without the risk of inducing hypoglycemia (low blood sugar levels).

SHINE is a multicenter, randomized, controlled clinical trial of 1400 participants that will include approximately 60 sites across the country. The trial will evaluate if blood sugar control is safe and effective for improving stroke recovery. The research sites will be testing the current standard treatment against the administration of a controlled IV insulin infusion therapy in eligible participants who present within 12 hours of the onset. The treatment lasts for up to three days.

Eligible participants will have a history of diabetes or may have undiagnosed diabetes and elevated blood glucose on initial evaluation and will have to get to the hospital very quickly after the start of symptoms. The study researchers are trying to understand the best way to manage blood sugar after a stroke to improve recovery.

The pancreas is a long, slender organ, most of which is located posterior to the bottom half of the stomach (Figure). Although it is primarily an exocrine gland, secreting a variety of digestive enzymes, the pancreas has an endocrine function. Its pancreatic islets—clusters of cells formerly known as the islets of Langerhans—secrete the hormones glucagon, insulin, somatostatin, and pancreatic polypeptide (PP). Beta cells are pancreatic islet cell type that produces the hormone insulin.

The pancreatic exocrine function involves the acinar cells secreting digestive enzymes that are transported into the small intestine by the pancreatic duct. Its endocrine function involves the secretion of insulin (produced by beta cells) and glucagon (produced by alpha cells) within the pancreatic islets. These two hormones regulate the rate of glucose metabolism in the body. The micrograph reveals pancreatic islets. LM × 760.

Regulation of Blood Glucose Levels by Insulin and Glucagon

Glucose is required for cellular respiration and is the preferred fuel for all body cells. The body derives glucose from the breakdown of the carbohydrate-containing foods and drinks we consume. Glucose not immediately taken up by cells for fuel can be stored by the liver and muscles as glycogen, or converted to triglycerides and stored in the adipose tissue. Hormones regulate both the storage and the utilization of glucose as required. Receptors located in the pancreas sense blood glucose levels, and subsequently the pancreatic cells secrete glucagon or insulin to maintain normal levels.

Impaired insulin function can lead to a condition called diabetes mellitus, the main symptoms of which are illustrated in Figure 37.10. This can be caused by low levels of insulin production by the beta cells of the pancreas, or by reduced sensitivity of tissue cells to insulin. This prevents glucose from being absorbed by cells, causing high levels of blood glucose, or hyperglycemia (high sugar). High blood glucose levels make it difficult for the kidneys to recover all the glucose from nascent urine, resulting in glucose being lost in urine. High glucose levels also result in less water being reabsorbed by the kidneys, causing high amounts of urine to be produced; this may result in dehydration. Over time, high blood glucose levels can cause nerve damage to the eyes and peripheral body tissues, as well as damage to the kidneys and cardiovascular system. Oversecretion of insulin can cause hypoglycemia, low blood glucose levels. This causes insufficient glucose availability to cells, often leading to muscle weakness, and can sometimes cause unconsciousness or death if left untreated.

When blood glucose levels decline below normal levels, for example between meals or when glucose is utilized rapidly during exercise, the hormone glucagon is released from the alpha cells of the pancreas. Glucagon raises blood glucose levels, eliciting what is called a hyperglycemic effect, by stimulating the breakdown of glycogen to glucose in skeletal muscle cells and liver cells in a process called glycogenolysis. Glucose can then be utilized as energy by muscle cells and released into circulation by the liver cells. Glucagon also stimulates absorption of amino acids from the blood by the liver, which then converts them to glucose. This process of glucose synthesis is called gluconeogenesis. Glucagon also stimulates adipose cells to release fatty acids into the blood. These actions mediated by glucagon result in an increase in blood glucose levels to normal homeostatic levels. Rising blood glucose levels inhibit further glucagon release by the pancreas via a negative feedback mechanism. In this way, insulin and glucagon work together to maintain homeostatic glucose levels, as shown in Figure 37.11.