Glucose is the main sugar found in our blood and is an important source of energy. Blood glucose levels measure the amount of glucose in your blood at a given time. It is most often used as a way to determine whether or not you have diabetes. A normal blood glucose level indicates that your body is properly processing and using foods. Your levels will change throughout the day depending on when you eat, how much you eat, what kind of foods you eat, and whether or not you exercise.
Identification
Blood glucose levels measure the amount of glucose (sugar) in your blood. When you eat food your body breaks down the food into energy. When you eat carbohydrates like breads, pastas, fruits, and candy, your body can quickly break them down into glucose that can be used by the body. Glucose is sent into the bloodstream where it can then be taken in and used by all of the cells in the body. The brain uses glucose as its primary fuel source. It cannot store it for later use so it needs a routine supply of glucose in the bloodstream to keep you going mentally and physically throughout the day.
Process
The two most common ways to measure glucose levels are by using blood or urine.
When doing a blood draw, the blood is either sent away for testing or is tested immediately using a blood glucose meter. The blood is placed on a test strip. The strips have chemicals on them which react with glucose. The strip is inserted into the meter which then displays the numerical blood glucose level for you right away.
A urine sample can be tested for the presence of glucose as well. The urine is tested using a color changing dipstick. The chemicals on the dipstick react with glucose. The color the dipstick changes indicates how much glucose is in your urine.
Effects
Glucose levels can be affected by when you eat, the types of foods that you eat (carbohydrates vs. proteins vs. fats), how often you eat, how much you eat at a given time, exercise, exercise intensity, stress, and disease processes. If you were to test your blood glucose level immediately after waking up it would be much lower than if you checked it at noon. Your body hasn't gotten any food for over six hours.
When it comes to exercise, exercising requires energy. Your body uses glucose for quick energy when you exercise. The harder and longer you exercise, the more energy you need, the more glucose you use thus lowering your overall blood glucose levels.
Signficance
Typically, blood glucose levels are ordered after an eight to 10 hour fast. A normal fasting blood glucose level ranges from 70 to 99 mg/dL. Impaired glucose tolerance, or pre-diabetes, is determined from fasting blood glucose levels ranging from 100 to 125 mg/dL. Fasting levels over 126 mg/dL are generally an indicator for diabetes.
Nonfasting normal blood glucose levels are normal up to 139 mg/dL, high from 140-199 mg/dL and an indicator for diabetes if over 200 mg/dL.
Results
Results out of the normal range are typically retested by the doctor before a diagnosis is made. Higher than normal levels can occur due to stress, renal failure, certain drugs, pancreatitis, certain cancers, excessive food intake, hyperthyroidism, and diabetes. Lower than normal levels can occur due to adrenal insufficiency, certain drugs, liver disease, hypothyroidism, excessive insulin intake, and starvation.
Glucose is not normally found in urine. Glucose in urine is abnormal and is generally an indicator for diabetes.
References
- "Krause's Food, Nutrition, & Diet Therapy 11th ed."; L. Kathleen Mahan and Sylvia Escott-Stump; 2004.
- Lab Tests Online: Glucose.
- The Franklin Institute, Resources for Science Learning: The Human Brain.
- U.S. National Library of Medicine, National Institutes of Health, Medline Plus: Glucose test.
- National Kidney Foundation: Kidney Early Evaluation Program.
