Diabetes Testing

Diabetes testing is a set of bloodwork exams that measures the amount of glucose in the blood, a key indicator if someone has prediabetes, type 1 diabetes or type 2 diabetes. Physicians test people who show one or more symptoms, have one or more risk factors or are pregnant.

Last Modified: September 5, 2023
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Who Should Test for Diabetes?

Your medical practitioner may include glucose testing as a routine part of your annual physical or wellness check. Your doctor may also check your blood glucose levels if you are someone at risk of developing diabetes.

Key risk factors include a family history of diabetes, patients with polycystic ovarian syndrome, and those who have medical conditions such as high cholesterol, high blood pressure or heart disease. Some demographics are also statistically at higher risk, including people more than 45 years of age and African American, Hispanic, Asian and Native American populations.

Your physician may recommend glucose testing if you experience symptoms of diabetes, such as:
  • Excessive thirst or hunger
  • Unexplained weight loss
  • Blurred vision
  • Feeling of lethargy
  • Loss of feeling or tingling in the hands or feet
  • Sores that don’t heal quickly
  • Dry skin
  • An unusual number of infections

Glucose testing is essential in the management of prediabetes and diabetes after a diagnosis.

For pregnant women, doctors sometimes order glucose testing to check for gestational diabetes, a type of diabetes that occurs during pregnancy because of hormonal changes. Left untreated, gestational diabetes can be harmful to the fetus and mother, and it increases the risk of developing diabetes later.

Type 1, Type 2 and Prediabetes Tests

Various tests can detect if someone has diabetes or prediabetes. A prompt and definitive diagnosis is essential so that your doctor can determine the appropriate treatment.

Doctors can use the Diabetes Autoantibody Panel test to determine if a patient has Type 1 diabetes. The presence of antibodies typically indicates Type 1. If the panel detects no antibodies, then you may have Type 2 diabetes.

Before taking a diabetes antibody panel test, you must take a fasting plasma glucose test, a random glucose test or an oral glucose tolerance test.

Doctors use the A1C or fasting plasma glucose (FPG) test to diagnose diabetes. In some situations, a random plasma glucose (RPG) test can be used for diabetes diagnosis.

Random Blood Sugar Test

A random blood sugar (RBG) test, or casual blood glucose test, measures blood glucose regardless of when you last ate. Medical professionals sometimes use an RPG test to diagnose diabetes in cases where symptoms are present and they do not want to wait until you have fasted. You do not need to fast overnight to take an RPG test.

Doctors order an RBG test if you show signs of diabetes. This blood glucose test is mainly used for monitoring people that already have diabetes. Random blood sugar tests can also be necessary if you experience any symptoms of diabetes.

A random blood glucose test can be performed at any time throughout the day. Results determine the need for more tests.

Random testing is crucial in healthy individuals because their glucose levels do not vary widely throughout the day. When blood glucose levels vary widely, it means there is a problem.

A1C Test

The A1C test — or HbA1c test or hemoglobin A1C test — measures average blood sugar levels over the past three months. Doctors most commonly use A1C tests to diagnose diabetes and prediabetes.

Higher A1C levels are associated with diabetes complications, so attaining and maintaining your individualized A1C goal is essential for those who have diabetes. Sugar in the bloodstream attaches to hemoglobin, and people who have higher blood sugar levels will have more sugar-coated hemoglobin.

People with diabetes should take an A1C test twice a year — more often if they have other medical conditions or their medicine changes. Your doctor will advise you on how often you should have this test.

A1C testing is performed in a lab or a doctor’s office using blood from the arm or finger stick. You do not have to prepare for this test, but you should consult your doctor if additional tests will be performed at the same time and whether you have to prepare for them.

Fasting Blood Sugar Test

The fasting blood sugar (FBS) test is a diabetes exam that measures blood glucose levels after you haven’t eaten for at least eight hours after your last meal. FBS is usually the first test carried out to check for diabetes and prediabetes.

Apart from testing for diabetes, the fasting blood sugar test is also used to test for the effectiveness of dietary changes or different medications on people diagnosed with diabetes. Your doctor will ask you to refrain from eating and from drinking except water for at least eight hours.

Glucose Tolerance Test

The glucose tolerance test measures how the body moves sugar from blood tissues. Your doctor will ask you to take a specific amount of glucose in liquid form, then draw and test your blood every 30 to 60 minutes. The test may run up to three hours.

This is a fasting test. For the few days leading to your glucose tolerance test, eat and drink normally and then fast (no meals and no liquids other than water) within eight to 10 hours before the blood test.

Ketone Testing

Ketone testing helps monitor people at a higher risk of developing ketones, especially those with Type 1 or Type 2 diabetes. The body burns sugar or glucose for energy production, and when the level of glucose is not enough, then your body will burn fat instead, resulting in the production of ketones, which show up in your urine and blood.

People are at risk of developing ketones if they:
  • Have a digestive disorder
  • Suffer from an eating disorder
  • Have a low-carbohydrate diet
  • Experience chronic diarrhea and vomiting
  • Take part in strenuous exercise
  • Are pregnant

Ketones in the urine are an indication that you are not getting adequate insulin. High levels of ketones indicate diabetic ketoacidosis (DKA), a serious complication of diabetes that can result in a coma or death.

Gestational Diabetes Tests

Doctors routinely test for gestational diabetes, a form of diabetes that begins or occurs during pregnancy, between the 24th and 28th weeks of pregnancy. Glucose screening tests are a normal part of pregnancy checkups.

While presenting with symptoms of gestational diabetes is rare, those that do experience symptoms such as increased thirst may be tested earlier. Doctors may also test patients earlier if they have an increased risk of developing gestational diabetes or have had gestational diabetes in previous pregnancies.

Testing is crucial because a pregnant mother should start any treatment immediately to protect her health and her baby’s. Treatment often includes following a prescribed gestational diabetes diet with follow up testing to monitor progress.

Glucose Screening Test

A glucose screening test checks blood glucose levels in pregnant women. It may be a one-step testing or a two-step testing process.

  • One-step testing: Fast for eight to 14 hours before the two-hour test. Your doctor will have you drink a liquid containing glucose, then draw your blood two times after every 60 minutes.
  • Two-step testing: Fast for eight to 14 hours ahead of time. Drink a glucose-containing liquid, then the doctor will draw your blood no more than one hour later. If results from your initial test show high levels of blood glucose, you will have to undergo a three-hour glucose tolerance test.

Diabetes Prevention

Diabetes is one of the leading chronic diseases that affect the population today. Physicians are stepping up screenings with the hope of preventing future cases and sharing critical information about how to prevent diabetes with the public.

Working closely with your doctor, you may be able to prevent Type 2 diabetes. Diabetes statistics indicate that with the guidance of medical professionals like registered dietitians, a diabetes diet and safely developed exercise plan can be beneficial.

Early detection of prediabetes can help slow development and even reverse the condition and potentially avoid future diabetic complications, which can be severe. These include heart disease and stroke, diabetic retinopathy and blindness, kidney disease and vascular problems leading to the amputation of limbs.

Please seek the advice of a medical professional before making health care decisions.