Table of ContentsView All
View All
Table of Contents
Purpose
Risks and Contraindications
Before the Test
During the Test
After the Test
Interpreting Results
Frequently Asked Questions
The fasting plasma glucose (FPG) test, also known as the fasting blood glucose test (FBG) or fasting blood sugar test, measures the levels of glucose (sugar) in the blood. It is a relatively simple, accurate, and inexpensive test that can screen for diabetes and problems withinsulinfunctioning.
Purpose of Test
The FPG test is recommended as a screening test for people 35 or older to be repeated every three years. It may also be used for people who havesymptoms of diabetesor multiple risk factors for diabetes.
Lack of insulin or insulin resistance causes higher than normal levels of glucose in the blood.
In the diagnosis of diabetes, the FPG test may be performed alone or along with one of these other tests:
If your healthcare provider is recommending the FPG test because you’ve been having symptoms of diabetes, you can expect it will need to be repeated on a different day to confirm the results.Your healthcare provider may recommend the OGTT or the hemoglobin A1C test instead of or in addition to a second FPG test.
The FPG test is regarded as accurate and more sensitive than the A1C, though it is not quite as sensitive as the gold standard of glucose tests, the OGTT.
A key difference between the FPG test and the OGTT is the OGTT cannot be used to monitor or measure the effectiveness of a diabetes management program in those who have already been diagnosed with the disease.
As a standard blood draw performed in a lab, the FPG test is considered safe.
A handful of potential risks are associated with any blood work:
You should be able to drink water at any time before your test, and you will be instructed to avoid food or other drinks for about eight hours before your test. Your healthcare provider will advise you about any medication adjustments you might need to make before your test. If you have any questions about the test, ask your healthcare provider at this time.
Timing
The FPG test requires that you be in a fasted state—having not eaten anything for at least eight hours—so the test is usually scheduled for earlier in the morning.Once the lab technician is prepped to draw your blood, the test takes about five minutes.
Location
The test will usually take place in a lab, hospital, or your healthcare provider’s office.
What to Wear
Short sleeves are helpful for a blood draw in your arm, but not absolutely necessary. Dress comfortably and make sure you can push up your shirt sleeve or remove a layer of clothing.
Food and Drink
Cost and Health Insurance
While the price may vary depending on where the test is performed, the FPG test is not expensive. Most health insurance policies cover the cost of FPG for routine examinations, monitoring, or for the purpose of diagnosing diabetes. You may be responsible for a co-pay or co-insurance fee. Call yourinsurance companyto determine if you will have any out-of-pocket expenses for the test.
What to Bring
Bring your insurance card, identification, and a copy of the lab request/referral form. You might also want to bring a book or magazine in case you get stuck in the waiting room.
Some people feel woozy from having blood drawn after a long fast, due to a drop in blood sugar. To avoid this, bring along a snack to eat right after your test is complete.
Other Considerations
A quick web search will bring up numerous FPG testing kits you can order at home. While these may be helpful for monitoring diabetes after it’s been diagnosed, they are not recommended for diagnosing or screening for diabetes.
Pre-Test
Once you arrive, check-in at the front desk. You may need to fill out insurance billing forms or consent forms.
If you’re nervous about having blood work done or have a history of feeling faint after medical procedures, make sure you tell someone so that the lab tech or nurse can take special precautions.
Throughout the Test
The technician or person administering the test will collect either:
Your blood sample will be sent to a lab for analysis, and sometimes a finger prick test can provide immediate results.
Try not to cross your legs or tense your body, because stress can raise your glucose levels or make extracting blood more difficult.
Venous Blood Sample
The technician will ask you which arm you prefer to use for the test—most people choose their non-dominant arm.
Tell the technician if you start to feel woozy or lightheaded. It can help to look away from the blood collection if necessary.
Finger Prick
If you’re having your fasting glucose levels monitored, you may just need a finger prick in the office. This point-of-care test usually gets quick results and is only slightly uncomfortable, not painful.
7 Tips to Make Getting Blood Drawn Painless
Post-Test
As long you’re not feeling faint or weak, you should be free to leave as soon as the test is complete. If you’re feeling dizzy, you may be asked to sit in the waiting room for a few minutes. This would be the time to have a snack to replenish low blood sugar levels as a result of fasting.
After your blood draw, you can head home or get back to your day.
Managing Side Effects
Keep an eye on the puncture site to make sure the bleeding has stopped; note if there’s any bruising, swelling, or signs of infection (warmth, or redness). Bruising should go away on its own in a few days, but swelling and infection may require medical attention.
Depending if your test took place in your healthcare provider’s office or in a lab, results may take anywhere from the same day to up to a week to arrive.
Diagnostic categories are based onglucose levels in the bloodand include the following, measured in milligrams per deciliter (mg/dL).
If your FPG test results are borderline or elevated and indicate diabetes, the test will need to be repeated a second time in the near future or other tests might be performed, such as the hemoglobin A1C test, oral glucose tolerance test, or the postprandial plasma glucose test.
A healthcare professional should consider a person’s full medical history when conducting this test and interpreting the results.
Depending on your confirmed results, there are several courses of action.
High FPG and Symptoms of High Blood Sugar
If you are experiencing symptoms of elevated blood sugar and your FPG reading is above 126 mg/dL, that may be enough evidence for your healthcare provider to confirm your diagnosis of diabetes.
In that case, you and your healthcare provider will discuss setting up a treatment plan. Depending on the type of diabetes you have, it may include regular glucose monitoring, medication, and supplements, along with lifestyle changes, such as a whole foods, low-carb diet, exercise, and stress reduction practices.
There are several reasons for having a high FPG that may not be due to diabetes:
Your healthcare provider will be able to track your symptoms and perform more tests to rule these other conditions out if necessary.
Borderline/Prediabetes
If your FPG reading is between 100 mg/dL to 126 mg/dL, the American Diabetes Association recommends that regular screening for diabetes be repeated yearly.Having prediabetes doesn’t mean you’ll automatically develop type 2 diabetes, however. Prediabetes (and type 2 diabetes, for that matter) are reversible conditions.
What Are Tests for Prediabetes?
Low FPG and Symptoms of Low Blood Sugar
An FPG reading below 70 mg/dL is considered hypoglycemia. In a person without diabetes, signs and symptoms may not occur until plasma glucose concentrations drop below 55 mg/dl.
Hypoglycemia could mean you’ve developed one of the following conditions:
Monitoring
Depending on your results, if you’re using the FPG test to monitor your diabetes, your healthcare provider may want to adjust your medication or treatment plan.
If you’re diagnosed with diabetes based on confirmed readings from an FPG test, your healthcare provider will define which type of diabetes you have. The types are treated differently.
Whether a person has type 1, type 2, or gestational diabetes, a healthy lifestyle helps insulin to work better.
Keep an open dialogue with your healthcare provider about your results from the FPG test and what steps you should take next.
Type 2 Diabetes Doctor Discussion GuideGet our printable guide for your next healthcare provider’s appointment to help you ask the right questions.Download PDFEmail AddressSign UpThank you, {{form.email}}, for signing up.There was an error. Please try again.
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What Is Type 1 Diabetes?
A Word From Verywell
The fasting blood glucose test is a noninvasiveblood testthat can be used to determine diabetes risk, diagnose diabetes, and evaluate blood sugar and insulin function in people who have diabetes. Abnormal results can help guide you to make lifestyle changes and determine medication adjustments if needed.
Besides the fasting glucose plasma test, another blood test that requires fasting includes a lipid test or lipid profile.This type of test measures triglyceride and cholesterol levels in the blood to assess the risk of heart disease. It can tell you the levels of “good” cholesterol(HDL)and “bad” cholesterol(LDL)in your blood.
15 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.American Diabetes Association.2. Classification and diagnosis of diabetes: Standards of medical care in diabetes—2022.Diabetes Care. 2022;45(Supplement 1):S17-S38. doi:10.2337/dc22-S002American Diabetes Association.Hypoglycemia (Low Blood Sugar).American Diabetes Association.Diabetes Overview: Diagnosis.National Institute of Diabetes and Digestive and Kidney Diseases.Diabetes and Prediabetes Tests.American Diabetes Association.6. Glycemic targets: Standards of medical care in diabetes—2022.Diabetes Care. 2022;45(Supplement 1):S83–S96. doi:10.2337/dc22-S006National Institute of Diabetes and Digestive and Kidney Diseases.Cushing’s Syndrome.Kikuta K, Masamune A, Shimosegawa T.Impaired glucose tolerance in acute pancreatitis.World J Gastroenterol.2015;21(24):7367-74. doi:10.3748/wjg.v21.i24.7367Wernly B, Lichtenauer M, Hoppe UC, Jung C.Hyperglycemia in septic patients: an essential stress survival response in all, a robust marker for risk stratification in some, to be messed with in none.J Thorac Dis. 2016;8(7):E621-4. doi:10.21037/jtd.2016.05.24Ishihara M.Acute hyperglycemia in patients with acute myocardial infarction.Circ J.2012;76(3):563-71. doi:10.1253/circj.cj-11-1376Galati SJ, Rayfield EJ.Approach to the patient with postprandial hypoglycemia.Endocr Pract. 2014;20(4):331-40. doi:10.4158/EP13132.RADesimone ME, Weinstock RS.Non-diabetic hypoglycemia. In: Feingold KR, Anawalt B, Boyce A, et al., editors.Endotext[Internet]. South Dartmouth (MA): MDText.com, Inc.MedlinePlus.Fasting for a Blood Test.MedlinePlus.Cholesterol Levels.Van Ness-Otunnu R, Hack JB.Hyperglycemic crisis. J Emerg Med. 2013;45(5):797-805. doi:10.1016/j.jemermed.2013.03.040MedlinePlus.Blood Sugar Test.
15 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.American Diabetes Association.2. Classification and diagnosis of diabetes: Standards of medical care in diabetes—2022.Diabetes Care. 2022;45(Supplement 1):S17-S38. doi:10.2337/dc22-S002American Diabetes Association.Hypoglycemia (Low Blood Sugar).American Diabetes Association.Diabetes Overview: Diagnosis.National Institute of Diabetes and Digestive and Kidney Diseases.Diabetes and Prediabetes Tests.American Diabetes Association.6. Glycemic targets: Standards of medical care in diabetes—2022.Diabetes Care. 2022;45(Supplement 1):S83–S96. doi:10.2337/dc22-S006National Institute of Diabetes and Digestive and Kidney Diseases.Cushing’s Syndrome.Kikuta K, Masamune A, Shimosegawa T.Impaired glucose tolerance in acute pancreatitis.World J Gastroenterol.2015;21(24):7367-74. doi:10.3748/wjg.v21.i24.7367Wernly B, Lichtenauer M, Hoppe UC, Jung C.Hyperglycemia in septic patients: an essential stress survival response in all, a robust marker for risk stratification in some, to be messed with in none.J Thorac Dis. 2016;8(7):E621-4. doi:10.21037/jtd.2016.05.24Ishihara M.Acute hyperglycemia in patients with acute myocardial infarction.Circ J.2012;76(3):563-71. doi:10.1253/circj.cj-11-1376Galati SJ, Rayfield EJ.Approach to the patient with postprandial hypoglycemia.Endocr Pract. 2014;20(4):331-40. doi:10.4158/EP13132.RADesimone ME, Weinstock RS.Non-diabetic hypoglycemia. In: Feingold KR, Anawalt B, Boyce A, et al., editors.Endotext[Internet]. South Dartmouth (MA): MDText.com, Inc.MedlinePlus.Fasting for a Blood Test.MedlinePlus.Cholesterol Levels.Van Ness-Otunnu R, Hack JB.Hyperglycemic crisis. J Emerg Med. 2013;45(5):797-805. doi:10.1016/j.jemermed.2013.03.040MedlinePlus.Blood Sugar Test.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
American Diabetes Association.2. Classification and diagnosis of diabetes: Standards of medical care in diabetes—2022.Diabetes Care. 2022;45(Supplement 1):S17-S38. doi:10.2337/dc22-S002American Diabetes Association.Hypoglycemia (Low Blood Sugar).American Diabetes Association.Diabetes Overview: Diagnosis.National Institute of Diabetes and Digestive and Kidney Diseases.Diabetes and Prediabetes Tests.American Diabetes Association.6. Glycemic targets: Standards of medical care in diabetes—2022.Diabetes Care. 2022;45(Supplement 1):S83–S96. doi:10.2337/dc22-S006National Institute of Diabetes and Digestive and Kidney Diseases.Cushing’s Syndrome.Kikuta K, Masamune A, Shimosegawa T.Impaired glucose tolerance in acute pancreatitis.World J Gastroenterol.2015;21(24):7367-74. doi:10.3748/wjg.v21.i24.7367Wernly B, Lichtenauer M, Hoppe UC, Jung C.Hyperglycemia in septic patients: an essential stress survival response in all, a robust marker for risk stratification in some, to be messed with in none.J Thorac Dis. 2016;8(7):E621-4. doi:10.21037/jtd.2016.05.24Ishihara M.Acute hyperglycemia in patients with acute myocardial infarction.Circ J.2012;76(3):563-71. doi:10.1253/circj.cj-11-1376Galati SJ, Rayfield EJ.Approach to the patient with postprandial hypoglycemia.Endocr Pract. 2014;20(4):331-40. doi:10.4158/EP13132.RADesimone ME, Weinstock RS.Non-diabetic hypoglycemia. In: Feingold KR, Anawalt B, Boyce A, et al., editors.Endotext[Internet]. South Dartmouth (MA): MDText.com, Inc.MedlinePlus.Fasting for a Blood Test.MedlinePlus.Cholesterol Levels.Van Ness-Otunnu R, Hack JB.Hyperglycemic crisis. J Emerg Med. 2013;45(5):797-805. doi:10.1016/j.jemermed.2013.03.040MedlinePlus.Blood Sugar Test.
American Diabetes Association.2. Classification and diagnosis of diabetes: Standards of medical care in diabetes—2022.Diabetes Care. 2022;45(Supplement 1):S17-S38. doi:10.2337/dc22-S002
American Diabetes Association.Hypoglycemia (Low Blood Sugar).
American Diabetes Association.Diabetes Overview: Diagnosis.
National Institute of Diabetes and Digestive and Kidney Diseases.Diabetes and Prediabetes Tests.
American Diabetes Association.6. Glycemic targets: Standards of medical care in diabetes—2022.Diabetes Care. 2022;45(Supplement 1):S83–S96. doi:10.2337/dc22-S006
National Institute of Diabetes and Digestive and Kidney Diseases.Cushing’s Syndrome.
Kikuta K, Masamune A, Shimosegawa T.Impaired glucose tolerance in acute pancreatitis.World J Gastroenterol.2015;21(24):7367-74. doi:10.3748/wjg.v21.i24.7367
Wernly B, Lichtenauer M, Hoppe UC, Jung C.Hyperglycemia in septic patients: an essential stress survival response in all, a robust marker for risk stratification in some, to be messed with in none.J Thorac Dis. 2016;8(7):E621-4. doi:10.21037/jtd.2016.05.24
Ishihara M.Acute hyperglycemia in patients with acute myocardial infarction.Circ J.2012;76(3):563-71. doi:10.1253/circj.cj-11-1376
Galati SJ, Rayfield EJ.Approach to the patient with postprandial hypoglycemia.Endocr Pract. 2014;20(4):331-40. doi:10.4158/EP13132.RA
Desimone ME, Weinstock RS.Non-diabetic hypoglycemia. In: Feingold KR, Anawalt B, Boyce A, et al., editors.Endotext[Internet]. South Dartmouth (MA): MDText.com, Inc.
MedlinePlus.Fasting for a Blood Test.
MedlinePlus.Cholesterol Levels.
Van Ness-Otunnu R, Hack JB.Hyperglycemic crisis. J Emerg Med. 2013;45(5):797-805. doi:10.1016/j.jemermed.2013.03.040
MedlinePlus.Blood Sugar Test.
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