The amount of glucose, or sugar, in a person’s blood changes depending on food intake and exercise. A healthy amount of blood sugar depends on the time at which the glucose level is measured. Depending on the time of the test, a healthy glucose level is 70 to 145 milligrams per deciliter (mg/dL) (about 3.9 to 8.1 millimoles per liter (mmol/L)).
Glucose is provided to the body by intake of carbohydrate foods and is a main source of energy. Insulin is a hormone produced by the pancreas that assists the body’s cells in using blood sugar. When the amount of blood sugar in the body rises, insulin is released into the blood.
Blood sugar levels typically are measured in a laboratory. A blood sample is taken and the blood is then analyzed by a doctor. Results of this test are typically available within a few hours of the test. People with diabetes or others who need to keep track of their blood sugar level can purchase glucose meters to use at home. Home blood sugar test results usually vary from laboratory results due to meter calibration, size, and quality of blood sample, among other factors.
Different blood sugar tests are used to monitor glucose levels. Fasting blood glucose levels are those taken after eight or more hours without food. Normal blood sugar levels for a fasting test are 70 to 99 mg/dL (about 3.9 to 5.5 mmol/L). Blood sugar tests taken two hours after the start of a meal are called postprandial tests and have a normal range of 70 to 145 mg/dL (about 3.9 to 8.1 mmol/L). Random blood sugar tests are taken at different times of day without regard to food consumption and have a normal range of 70 to 125 mg/dL (about 3.9 to 6.9 mmol/L).
Having an unusually low blood sugar level is called hypoglycemia. Symptoms of hypoglycemia include nausea, hunger, sweating, and headache. More extreme cases of hypoglycemia are typified by mood changes, dizziness, and blurred vision. Hypoglycemia is treated by consumption of sugar to restore the blood sugar levels. Low blood sugar levels are common in people who have diabetes.
Hyperglycemia, or high blood sugar, is a key symptom of diabetes. The two types of diabetes affect the body in different ways. In type 1 diabetes, the body’s immune system attacks the insulin-producing cells in the pancreas. Type 2 diabetes is characterized by the cells in the body becoming immune to insulin. In both cases, the body is left without enough insulin to assist the cells in absorbing glucose.