Does this test have other names?
Blood sugar, self-monitoring of blood glucose (SMBG), fasting plasma glucose (FPG),
random plasma glucose
What is this test?
A blood glucose test is a blood test that tells you if your level of glucose, or blood
sugar, is within a healthy range. Fasting plasma glucose, or FPG, is a common test
used to diagnose and monitor diabetes or prediabetes.
Why do I need this test?
You may need this test if you have symptoms of diabetes. These include increased thirst,
unexplained weight loss, increased urination, tiredness, blurred vision, and sores
that don't heal. Sometimes people with prediabetes or diabetes don't have any symptoms.
If you are overweight, obese, or have other risk factors for diabetes like high blood
sugar, your healthcare provider may recommend this test. Other risk factors for diabetes
include high blood pressure, high cholesterol, physical inactivity, and a family history
of diabetes. The U.S. Preventive Services Task Force recommends that adults ages 40
to 70 who are obese or overweight have their blood glucose checked at least every
3 years as long as their results are normal. All adults should be tested for diabetes
every 3 years beginning at age 45, no matter what their weight.
If you are pregnant, you will be screened for gestational diabetes between 24 and
28 weeks. If you have gestational diabetes, you will be checked more often during
your pregnancy and again after your pregnancy.
What other tests might I have along with this test?
Other tests that are used to diagnose diabetes or monitor blood glucose include a
hemoglobin A1C blood test. A variation on the blood glucose test that is also sometimes
used is called an oral glucose tolerance test, or OGTT. Because heart health is so
closely tied to diabetes, regular checks of blood pressure, cholesterol, and triglycerides
are important, too.
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used
for the test, and other things. Your test results may not mean you have a problem.
Ask your healthcare provider what your test results mean for you.
Target blood glucose ranges vary from person to person. If you have diabetes, the
American Diabetes Association's target blood glucose reading for you if you're not
pregnant is between 70 and 130 milligrams per deciliter (mg/dL) before a meal. After
a meal, it should be less than 180 mg/dL. Levels that are lower or higher than these
may be a sign of blood sugar control problems.
For the FPG test, a level of 99 or below is normal. A level of 100 to 125 means you
may have prediabetes. A level of 126 or above means you may have diabetes and need
to do the test again on a different day to be sure. If you have an abnormal blood
glucose, your healthcare provider may recommend behavioral counseling to help you
eat better and get more exercise.
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
A number of factors, primarily diet, can affect blood glucose levels. Follow your
healthcare provider's instructions about when to check your blood glucose and what
to do before and after checking it.
How do I get ready for this test?
When your blood is drawn in an office, you typically need to fast for 8 hours before
the test. This means you should eat nothing and drink only water. When monitoring
your blood glucose levels at home, you will often be asked to check it at different
times, including before and after meals. Carefully follow your healthcare provider's
instructions for checking blood glucose levels at home.
Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements
you are taking. This includes medicines that don't need a prescription and any illicit
drugs you may use.