when your sugar levels are below normal
Blood sugar level (or blood sugar concentration) is the amount of glucose (a source of energy) present in your blood at any given time. A normal blood glucose level for a healthy person is somewhere between 72 mg/dL (3.8 to 4 mmol/L) and 108 mg/dL (5.8 to 6 mmol/L). It, of course, depends on every individual alone.