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 35 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, and other things. Your test results may be different depending on the lab used. They 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 80 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.
If you experience symptoms of severe increased thirst, frequent urination, unexplained weight loss, increased hunger, tingling of your hands or feet -- your doctor may run a test for diabetes.
According to the Centers for Disease Control and Prevention, some 29 million children and adults in the U.S., or over 9% of the population, have diabetes today. Yet, millions of Americans are unaware that they have diabetes, because there may be no warning signs.
To confirm the diagnosis of type 2 diabetes, your doctor will order a fasting plasma glucose test or a casual plasma glucose.
Diabetes and the Fasting Plasma Glucose Test
The fasting plasma glucose test (FPG) is the preferred method for diagnosing diabetes, because it is easy to do, convenient, and less expensive than other tests, according to the American Diabetes Association.
How Do I Prepare for the Blood Glucose Test?
Before taking the blood glucose test, you will not be allowed to eat anything for at least eight hours.
What Happens During the Blood Glucose Test?
During a blood glucose test, blood will be drawn and sent to a lab for analysis.
What Do the Results of the Blood Glucose Test Mean?
Normal fasting blood glucose -- or blood sugar -- is between 70 and 100 milligrams per deciliter or mg/dL for people who do not have diabetes. The standard diagnosis of diabetes is made when two separate blood tests show that your fasting blood glucose level is greater than or equal to 126 mg/dL.
However, if you have normal fasting blood sugar, but you have risk factors for diabetes or symptoms of diabetes, your doctor may decide to do a glucose tolerance test (see below) to be sure that you do not have diabetes.
Some people have a normal fasting blood sugar reading, but their blood sugar rapidly rises as they eat. These people may have impaired glucose tolerance. If their blood sugar levels are high enough, they may be diagnosed with diabetes.
The casual plasma glucose test is another method of diagnosing diabetes. During the test, blood sugar is tested without regard to the time since the person's last meal. You are not required to abstain from eating prior to the test. A glucose level greater than 200 mg/dL may indicate diabetes, especially if the test is repeated at a later time and shows similar results. The Casual Plasma Glucose Test for Diabetes
The Oral Glucose Tolerance Test for Diabetes
The oral glucose tolerance test is yet another method used to detect diabetes, but it is usually only done during pregnancy to diagnose gestational diabetes or for someone who is suspected of having type 2 diabetes yet has a normal fasting glucose level. It can also be performed to diagnose prediabetes.
Diabetes and the Hemoglobin A1c Test
The hemoglobin A1c test (also called the glycated hemoglobin test or HbA1c), is an important diabetes blood test used to determine how well your diabetes is being controlled. This diabetes test provides an average of your blood sugar control over a six- to 12-week period and is used in conjunction with home blood sugar monitoring to make adjustments in your diabetes medicines. The HbA1c level can also be used to diagnose diabetes if a value of equal to or greater than 6.5% is found.
Other Diabetes Tests
Along with the hemoglobin A1c test, it's important for people with diabetes to have a dilated eye exam at least once a year as part of a complete eye exam. This important test can detect early signs of retinopathy, which may have no symptoms at first. A foot exam once or twice a year -- or at every doctor's visit -- is also imperative to detect decreased circulation and sores that may not be healing. Early detection of eye and foot problems in diabetes allows your doctor to prescribe proper treatment when it is most effective.
Many children have no symptoms before they are diagnosed with type 2 diabetes. Most of the time, diabetes is discovered when a blood or urine test taken for other health problems shows diabetes. Talk to your doctor about your child's risk for diabetes. If your child's blood sugar tests are higher than normal, but not yet at the level of diabetes (called prediabetes), your doctor may instruct you in specific diet and exercise changes to help your child avoid getting diabetes altogether. Children with type 2 diabetes or prediabetes are almost always overweight or obese. Diabetes can cause major health problems if you do not keep your blood sugar in check. However, you can stay healthy and feel good despite your diagnosis if you follow your doctor's recommended treatment plan and maintain a healthy lifestyle. By choosing foods wisely, exercising regularly, maintaining a normal weight, reducing your stress level, and making other modest lifestyle changes, living with diabetes will be easier.Diabetes Testing in Children
Understanding Your Diabetes Diagnosis
What happens when blood glucose is too high?
What would cause my glucose levels to be high?
What is considered a high glucose level?