Blood sugar is also called blood glucose. It is a measurement of the amount of sugar in your blood. This measurement is found by doing a blood test, usually after an 8-hour fast. It is important to know this number because it tells your doctor or if you are at risk for diabetes or if you may have diabetes. [1-3]
Why Is Glucose Important?
Glucose is the sugar that your body uses for energy. You get glucose from foods called carbohydrates. These include fruits, vegetables, and grains as well as sugar added to foods. Your body stores some glucose to release when you need energy. 
In order for your cells to use glucose, it has to move from your blood into your cells. For that you need the hormone called insulin. Insulin comes from your pancreas. If your pancreas does not make enough insulin or if the insulin does not work properly, your blood sugar goes up. 
High blood sugar, called hyperglycemia, may be the first sign of type 2 diabetes. Even before type 2 diabetes, you may have an elevated blood sugar called prediabetes. Diagnosing diabetes or prediabetes is important because the sooner you start treatment, the more likely you can prevent the long-term damage to your eyes, kidneys, nerves, heart, and blood vessels, and prevent complications of diabetes like heart attacks and strokes. 
When Should You Have Blood Sugar Checked?
You can have prediabetes or diabetes for many years without having any symptoms. During this time hyperglycemia can be causing damage that could be prevented with treatment. For this reason, the American Diabetes Association recommends that everyone should have their blood sugar level check at age 45. 
If you have risk factors for diabetes or prediabetes, you should have your blood sugar checked before age 45. Risk factors include: [1-4]
- Being overweight
- Not getting enough exercise
- Having a family history of diabetes
- Having high blood pressure
For women, having a condition called polycystic ovary syndrome or having had diabetes during pregnancy are also risk factors. Your race may be a risk factor along with your blood lipid profile. Talk to your doctor about your risk for diabetes and prediabetes. [1-4]
When doctors check you for a problem before you have any symptoms it is called a screening test. The best screening test for high sugar levels is the fasting blood sugar test. This blood test, also called fasting plasma glucose, is done after you have been fasting for 8 hours. Glucose is measured in milligrams per deciliter (mg/dL). This is the normal range: [1,2]
- 70 to 90 mg/dL is normal. If your fasting blood glucose is normal, your doctor may repeat the test in one to three years.
- 100 to 125 mg/dL is called prediabetes or impaired fasting glucose.
- 126 mg/dL may be diabetes.
If your blood sugar is outside the normal range, your doctor may repeat your fasting blood sugar or do other tests to find out if you have diabetes or prediabetes. [1-4] Although it is much less common than hyperglycemia, your blood sugar may also be below the normal range, less than 70 mg/dL, called hypoglycemia. Causes of hypoglycemia include too much insulin, hormone disorders, and liver disease. 
The Importance of Screening for Blood Sugar
It is estimated that by 2025 almost 10 percent of Americans will have type 2 diabetes.  But right now, about one out of three people have prediabetes. Having prediabetes means you are at increased risk for type 2 diabetes as well as heart disease and stroke. Over 80 percent of people living with prediabetes do not know they have it, which is why knowing your blood sugar range is so important. 
The good news is that if you have the test and your doctor tells you that you have prediabetes, there is still time to prevent or delay type 2 diabetes, heart disease, and stroke. In fact, people with prediabetes that start a lifestyle change program may cut their risk of diabetes by about 60 percent. 
The two most important lifestyle changes are weight loss and exercise, and they are not that hard do. If you are overweight, you should lose about 5 to 7 percent of your body weight, about 10 pounds if you weigh 200 pounds. Exercising for 150 minutes per week is the other key. You can get there with a brisk walk for 30 minutes on five days out of your week. 
If you have reached age 45 or you have risk factors for prediabetes and diabetes, it is time to find out your blood sugar number. If your number is too high, now is the time to work with your doctor to get it back in the normal range. Lifestyle changes and sometimes medications may be needed. [1-4] There are also natural therapies and dietary approaches for lowering blood sugar.
See below for more information:
- Suffering from High Blood Sugar Symptoms? Use This Glycemic Index Food List
- The Best Metabolic Syndrome Diet
- Could This Diet for High Blood Sugar Be the Single Healthiest Diet for Everyone?
- Cleveland Clinic, Blood Glucose Test, https://my.clevelandclinic.org/health/diagnostics/12363-blood-glucose-test
- American Association for Clinical Chemistry, Glucose Tests, https://labtestsonline.org/tests/glucose-tests
- American Diabetes Association, Screening for Diabetes, https://care.diabetesjournals.org/content/25/suppl_1/s21
- CDC, Prediabetes, https://www.cdc.gov/diabetes/basics/prediabetes.html