Diabetes Tests

What are diabetes tests?

Diabetes, also known as diabetes mellitus, is a disease that affects how your body uses glucose (blood sugar). Glucose is your body's main source of energy. A hormone (a chemical messenger in your bloodstream that controls the actions of certain cells or organs) called insulin helps move glucose from your bloodstream into your cells.

If you have diabetes, your body can't make insulin or can't use it as well as it should, or both. Too much glucose stays in your blood and doesn't reach your cells. This can cause glucose levels to get too high, which can lead to serious health conditions. These may include heart disease, nerve damage, eye problems, and kidney disease.

Your blood glucose can also drop below what is healthy for you. If it drops very low, you could lose consciousness or have a seizure.

Diabetes tests most often measure glucose levels in your blood to monitor your blood glucose level or see if you have or are at risk for diabetes. Urine tests for diabetes are not used as much since they are not as accurate, and you would need a blood test to diagnose diabetes.

Other names: blood glucose, fasting plasma glucose, FPG, oral glucose tolerance test, OGTT, glucose screening test, glucose in urine test, hemoglobin A1c, random blood sugar, blood sugar, fasting blood sugar (FBS)

What are they used for?

Diabetes tests are used to screen, monitor, and/or diagnose the following:

• Type 1 diabetes. If you have type 1 diabetes, your body makes little or no insulin. This disease happens when your immune system attacks and destroys cells that produce insulin. It can develop at any age but most often starts in childhood. People with type 1 diabetes must take daily doses of insulin, either by injection or a special pump.
• Type 2 diabetes. This is the most common form of diabetes. If you have type 2 diabetes, your body may still be able to make insulin, but your cells don't respond well to insulin and can't easily take up enough glucose from your blood. Type 2 diabetes may be caused by your genes and lifestyle factors, such as being overweight or having obesity. The disease most often occurs in adulthood but is becoming more common in children and teens.
• Gestational diabetes. This is a form of diabetes that develops during pregnancy.
• Prediabetes. This is a condition in which your blood glucose levels are higher than what is healthy for you but not high enough to be considered diabetes. But having prediabetes raises your risk of getting type 2 diabetes later on.

Why do I need a diabetes test?

You may need testing to monitor your blood glucose level or if you have symptoms of diabetes, such as:

• Increased thirst
• Frequent urination
• Increased hunger
• Fatigue
• Blurred vision
• Unexplained weight loss
• Sores that are slow to heal
• Numbness or tingling in your feet

Symptoms of type 1 diabetes usually come on quickly and can be severe. Symptoms of type 2 diabetes and prediabetes often develop slowly, even over years.

Gestational diabetes doesn't usually cause symptoms in the early stages of your pregnancy, but you will most likely be screened for the condition between 24 and 28 weeks of pregnancy. If testing shows your glucose levels are too high, you will be tested again to confirm the diagnosis.

You may also need testing if you have certain risk factors for type 2 diabetes. You may be at higher risk for developing it if you:

• Are over 35 years old. The American Diabetes Association recommends diabetes screening for prediabetes and diabetes beginning at age 35 years and older.
• Have prediabetes.
• Are overweight or have obesity.
• Have a family history of diabetes.
• Have high blood pressure or heart disease.
• Previously had gestational diabetes.
• Exercise less than three times a week.
• Have non-alcoholic fatty liver disease (NAFLD).
• Are an African American, Hispanic or Latino, American Indian, or an Alaska Native.

What happens during a diabetes test?

There are several ways to screen for, monitor, and diagnose diabetes. Most tests involve measuring your blood glucose levels.

To get a blood sample, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

The different types of glucose blood tests include:

• Blood glucose test, also known as fasting blood glucose. Before the test, you will need to fast (not eat or drink) for eight hours before the test. This test is usually done in the morning and is often used as a screening test for diabetes. It may be repeated to confirm a diagnosis.
• Oral glucose tolerance test (OGTT). This test also requires fasting. When you arrive for your test, a blood sample will be taken. You will then drink a sugary liquid that contains glucose. About two hours later, another blood sample will be taken. This test tells your health care provider how well your body processes sugar. This test may be used to test for gestational diabetes. If you are having this test done during pregnancy, you will have your blood drawn every 30 minutes for two to three hours.
• Glucose challenge test, also known as the glucose screening test. This test may be used to test for gestational diabetes. You will drink a sugary liquid that contains glucose. A blood sample will be taken one hour later. You do not need to fast for this test. If your blood glucose is too high, your provider may order an oral glucose tolerance test.
• Random blood sugar. This test can be taken at any time. No fasting is required. This test may be used if you have symptoms of diabetes.
• Hemoglobin A1c (HbA1c). This test measures the average amount of glucose attached to hemoglobin over the past three months. Hemoglobin is the part of your red blood cells that carries oxygen from your lungs to the rest of your body. No fasting is required for this test.

Glucose may also be measured in your urine.

Urine tests are not often used to diagnose or monitor diabetes since blood tests are more accurate. But a urine test may show if you are at risk for getting the disease. If your glucose in urine levels are too high, then you will probably need a blood test to confirm the diagnosis.

For a glucose in urine test, your provider may recommend an at-home test kit. The kit will include a test strip that you hold under your stream of urine. The test strip will change colors to show different levels of glucose.

Will I need to do anything to prepare for this test?

You will need to fast (not eat or drink) for a blood glucose and an oral glucose tolerance test.

You don't need any special preparations for a random blood sugar test, glucose challenge test, hemoglobin A1c test, or glucose in urine test.

Are there any risks to this test?

There is very little risk to having a blood test. There may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

There is no risk to having a urine test.

What do the results mean?

Depending on the type of test or tests you had, your results may show one of the following:

• Your glucose is at a healthy level for you. This means you probably are not at risk for or do not have diabetes.
• Prediabetes.This means you have glucose levels that are higher than what is healthy for you and may be at risk of getting diabetes.
• Type 1 or type 2 diabetes.
• Gestational diabetes.

If you have been diagnosed with type 1 diabetes, talk to your provider about how to best manage the disease. There is no cure for type 1 diabetes, but it may be controlled with regular glucose monitoring and taking insulin.

If you've been diagnosed with prediabetes or type 2 diabetes, your condition may be managed or even reversed by taking diabetes medicines and making lifestyle changes. These include eating a healthy diet, losing weight, and increasing exercise.

If you've been diagnosed with gestational diabetes, you may be able to lower your glucose levels by eating a healthy diet and getting regular exercise. But be sure to talk to your provider about treatment options. Most of the time, gestational diabetes goes away after giving birth. But you will be at higher risk for developing type 2 diabetes in the future.

If you have other questions about your diabetes diagnosis or treatment, talk to your provider.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about diabetes testing?

If you've been diagnosed with type 1 diabetes, you will need to monitor your blood glucose levels daily, often several times a day. Your provider can recommend a kit you can use at home. Most kits include a lancet, a device that pricks your finger. You will use this to collect a drop of blood for testing. There are some newer kits available that don't require pricking your finger. If you are pregnant and have gestational diabetes, you may also need to monitor your glucose levels in this way.

People with type 2 diabetes must also check their blood sugar regularly. If you have type 2 diabetes, talk to your provider about how often it should be checked.

People with type 2 diabetes may also need to have their insulin levels checked regularly. Insulin plays a key role in keeping glucose at the right levels. An insulin in blood test is done at a provider's office.