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Hypoglycemia is defined as a blood glucose level below 70 milligrams per deciliter. This abnormally low glucose level can develop in individuals with type 1 diabetes who depend on insulin, as well as in those with type 2 diabetes using insulin or insulin-stimulating medications. It results from a mismatch between circulating insulin and the body's glucose demands.

In diabetes, especially with exogenous insulin, the body's natural counter-regulatory response is impaired. High insulin levels prevent the liver from releasing glucose, and externally administered insulin cannot be reduced during falling glucose levels. This blunted defense mechanism delays recovery from hypoglycemia and increases the risk of severe hypoglycemia, similar to complications of diabetes mellitus.

Early symptoms of hypoglycemia result from sympathetic nervous system activation and include tremor, sweating, palpitations, anxiety, tachycardia, and hunger. As blood glucose falls further, neuroglycopenic symptoms develop, such as confusion, dizziness, blurred vision, irritability, and poor concentration. Severe cases may progress to seizures or loss of consciousness.

Common risk factors for hypoglycemia include excessive insulin dosing, missed meals, and vigorous exercise without carbohydrate compensation. These situations create a mismatch where insulin levels exceed the body's glucose needs. Proper medication adjustment, meal planning, and physical activity management are essential for prevention.

In non-diabetic individuals, fasting or exercise lowers insulin levels and triggers counter-regulatory hormones like glucagon and epinephrine. These hormones raise hepatic glucose output and limit peripheral glucose uptake to maintain normoglycemia. This protective mechanism prevents blood glucose from dropping dangerously low during periods of reduced food intake or increased energy demand.

Immediate hypoglycemia produces acute symptoms like tremor, confusion, and seizures. Nocturnal hypoglycemia, occurring during sleep, may present with night sweats, nightmares, and morning headaches. In long-standing diabetes, reduced glucagon response and diminished warning signs can delay recognition of both types, making regular glucose monitoring critical.

Immediate treatment depends on consciousness level. If conscious, fast-acting carbohydrates should be administered to raise blood glucose quickly. If unconscious, intravenous glucose or glucagon injection is necessary. Prevention through proper medication adjustment, meal planning, regular glucose monitoring, and patient education helps reduce the frequency and severity of hypoglycemic episodes.