Adults. A normal blood sugar level is between 72 mg/dL and 108 mg/dL (4 to 6 mmol/L) for a healthy person. The concentration of glucose in the blood of a healthy person in the morning on an empty stomach is between 68 mg/dL and 108 mg/dL (3.8 and 6.0 mmol/L). 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.