Hypoglycemia (or hypoglycemic) unawareness is the inability to recognize early symptoms of low blood sugar until they become severe. Once symptoms reach this stage, urgent treatment is necessary to prevent further progression and life-threatening health problems, such as a seizure or stroke.

Severe symptoms of low blood sugar include confusion, slurred speech, unsteadiness when standing or walking, muscle twitching, and personality changes. People with diabetes who tightly control their blood sugar levels are more likely to have episodes of low blood sugar. Frequent and severe low blood sugar episodes are likely to evolve into hypoglycemia unawareness. Once a person has had one hypoglycemia unawareness episode, more are likely to occur.