What is the medical term for abnormally low blood sugar?

The medical term for abnormally low blood sugar is hypoglycemia. It generally describes a blood-glucose level below 70 mg/dL (3.9 mmol/L), although symptoms and clinical thresholds can vary by person and situation.

The brain depends heavily on glucose for energy, so falling levels may cause shakiness, sweating, hunger, anxiety, dizziness, confusion, difficulty speaking, seizures, or loss of consciousness. The body also responds by releasing hormones such as glucagon and adrenaline, which help raise glucose and can produce a racing heartbeat.

Hypoglycemia is especially common in people with diabetes who use insulin or certain glucose-lowering medicines. It can also result from fasting, alcohol use, severe illness, liver or kidney disease, hormone deficiencies, or rare insulin-producing tumors. The word combines Greek roots meaning “under,” “sweet,” and “blood.”