hyperglycemia

Hyperglycemia is simply too much sugar in the blood — like a river swollen past its banks. Normally the body keeps blood glucose within a narrow channel, but when insulin is missing or ineffective, the sugar that should have flowed into cells backs up in the bloodstream instead, rising to levels the vessels were never built to handle.

Technically, hyperglycemia is a plasma glucose concentration above the normal range — fasting values above about 5.6 mmol/L (100 mg/dL) are abnormal, and the diabetes threshold is 7.0 mmol/L (126 mg/dL) fasting. It arises when insulin secretion, insulin action, or both are inadequate, allowing the liver to overproduce glucose and tissues to underuse it. It is the defining feature of diabetes and the common target of all glucose-lowering treatment.

Short-term, very high glucose causes thirst, frequent urination, blurred vision, and fatigue, and at extremes can lead to ketoacidosis or a hyperosmolar state. Sustained over years, hyperglycemia is the engine of chronic complications, damaging the retina, kidneys, nerves, and blood vessels through processes such as protein glycation and oxidative stress. The goal of diabetes care is to lower glucose enough to prevent harm without causing dangerous hypoglycemia.