People with diabetes take insulin to lower high blood sugar. However, if glucose levels plunge too low -- from taking too much insulin or not eating enough sugar -- people can experience hypoglycemia, which can lead to dizziness, cognitive impairment, seizures or comas. To prevent and treat this condition, researchers report encapsulating the hormone glucagon. In mouse trials, the nanocapsules activated when blood sugar levels dropped dangerously low and quickly restored glucose levels.