The opposite of high blood glucose, very low blood glucose or hypoglycemia, is also dangerous. Hypoglycemia can occur when someone hasn't eaten enough to balance the effects of insulin or oral medicine. Prolonged, strenuous exercise in someone taking oral diabetes drugs or insulin also can cause hypoglycemia, as can alcohol. Someone whose blood glucose has become too low may feel nervous, shaky, and weak. The person may sweat, feel hungry, and have a headache.
Severe hypoglycemia can cause loss of consciousness.
A person with hypoglycemia who begins to feel weak and shaky should eat or drink something with sugar in it immediately, like orange juice. If the person is unconscious, he or she should be taken to a hospital emergency room right away. An identification bracelet or necklace that states that the wearer has diabetes will let friends know that these symptoms are a warning of illness that requires urgent medical help.