Diabetes Tests And Diagnosis

Diabetes is a condition that affects your body’s ability to produce and/or effectively use insulin. Your body uses insulin—a hormone produced by your pancreas—to convert glucose into energy. 

This form of diabetes is called diabetes mellitus. This should not be confused with a rare condition that affects your kidneys, called diabetes insipidus.

Doctors diagnose diabetes mellitus by checking your blood glucose levels. These levels are expressed as a number plus the unit of measurement mg/dL, which stands for milligrams per deciliter.

Types of diabetes mellitus

There are three types of diabetes: type 1, type 2, and gestational.

Type 1 diabetes

Type 1 diabetes is a chronic condition. With the exception of a pancreas transplant, there is no cure for this. However, it can be successfully managed through insulin, diet, and exercise.  

Type 1 is the least common form of diabetes in the US, and it can affect individuals of any age. It occurs in approximately 10 to 20 per 100,000 people in the US¹ per year. Overall, Type 1 accounts for 5% of all diabetes cases in the US.

Type 1 diabetes is considered a type of autoimmune disorder. A healthy immune system fights off viruses and harmful bacteria. If you have an autoimmune disorder, your immune system mistakenly attacks your body’s own healthy tissue. If you have type 1 diabetes, your immune system attacks the insulin-producing cells in your pancreas. There are over 80 types of autoimmune disorders.  

As with many autoimmune disorders, the exact cause of type 1 diabetes is unknown. While it is not inherited, some people are genetically predisposed to the disease. It can run in families, especially in individuals with other autoimmune diseases.  

Type 2 diabetes

Type 2 diabetes is the most common type of diabetes in the US. It is estimated that 35 million people² are diagnosed with it, while another seven million people likely have it but remain undiagnosed. 

Both genetic and lifestyle factors can play a role in developing this type of diabetes. You may be at an increased risk if you are overweight, eat a poor diet, and don’t get enough exercise. 

If you have type 2 diabetes, you can manage the condition through diet and exercise. You may need to take oral medication or insulin to control your blood sugar levels. 

Gestational diabetes

Gestational diabetes is a form of diabetes that can start during pregnancy. Each year in the US, gestational diabetes affects between 2% to 10% of pregnancies.³ 

The condition goes away on its own after the baby is born. If you continue to have higher than normal blood sugar levels after birth, you may have type 2 diabetes. In the US, half of all women who have gestational diabetes⁴ will go on to develop type 2 diabetes.

If you have gestational diabetes, you may be able to manage the condition through a healthy diet and exercise. Consult a certified dietician who can recommend a meal plan for you while you are pregnant and need to manage your diabetes. 

Talk to your doctor about physical activities to avoid during pregnancy. You will need to check your blood sugar on a regular basis. You may also have to take insulin if your blood sugar levels cannot be controlled with diet and exercise alone.

Prediabetes

If you have prediabetes, your blood sugar levels are above the normal range but are not high enough to meet the diagnostic criteria for diabetes. Prediabetes is common in the US, with approximately one in three adults⁵ having the condition. It is estimated that the vast majority of adults with prediabetes (80%) don’t know that they have it. 

What are the tests for diabetes?

There are two types of tests for diabetes: home tests and medical tests. 

Home tests for diabetes

If you are diagnosed with prediabetes or diabetes, you will use home tests to monitor your blood glucose levels. Home testing is done with either a glucometer or a continuous glucose monitor (CGM). 

Glucometer

You use a finger prick test to test your blood sugar levels with a glucometer. Place a drop of blood on a test strip and insert the strip into the glucometer machine. Your blood glucose reading will appear on the digital screen.

While anyone can purchase a glucometer, lancets (for doing the finger prick), and test strips over the counter, you should not use home testing as a way to diagnose yourself. You should only use home testing as part of your diabetic treatment plan prescribed by your doctor.

If you suspect you have diabetes, make an appointment to see your doctor.

Continuous glucose monitor

CGMs are small medical devices worn on the body, typically on the upper arm or the abdomen. Most CGMs take blood sugar readings every five minutes, around the clock. 

If you have a CGM, you can receive your blood sugar readings on a dedicated receiver or on your smartphone. You can also sync CGMs to an insulin pump to deliver insulin as your body needs it. 

Medical tests for diabetes

Medical tests are performed by a health professional in a clinic or hospital setting. Doctors use these tests to diagnose diabetes. Medical tests are also used to monitor blood sugar levels after a diabetes diagnosis.

Below are the medical tests that doctors commonly use to diagnose diabetes and/or monitor patients with the condition. Your doctor may order one or more tests to confirm or rule out a diabetes diagnosis.

Medical tests for type 1 and type 2 diabetes

If you are not pregnant and your doctor wants to check your blood sugar, there are several test options available.

HbA1C test

Your doctor may order an HbA1C test if they want to see a snapshot of your long-term blood sugar levels. This test averages your blood sugar levels over the past 90 days. 

The results of your HbA1C test are expressed in percentages: 

• A normal HbA1C is below 5.7%

• An HbA1C result of 5.7% to 6.4% indicates prediabetes

• A result of 6.5% or higher indicates diabetes

During an HbA1C test, a health professional will draw blood from your arm. This blood sample is then sent to a pathology lab for testing.

Fasting blood sugar test

Before a fasting blood sugar test, you can’t eat or drink anything other than water. 

• Normal: 99mg/dL or lower

• Prediabetes: 100 to 125mg/dL

• Diabetes: 126mg/dL and above

During a fasting blood sugar test, a health professional will draw blood. They may also prick your finger and use a glucometer to get a reading.

Random blood sugar test

If your doctor orders a random blood sugar test, you will not need to fast beforehand. This test involves a blood draw or a glucometer. In a random blood sugar test, any reading of 200 mg/dL or higher may indicate diabetes.

Glucose tolerance test

If your doctor orders a glucose tolerance test, you will need to fast beforehand. When you arrive at your appointment, a healthcare provider will draw blood. Then, you will drink a sugary solution. Your blood sugar level will then be tested again, usually two hours after you’ve finished drinking the solution.

Additional tests to confirm type 1 diabetes

If your test results confirm a diabetes diagnosis, your doctor may order additional tests to determine if you have type 1 or type 2. A type 1 diabetes diagnosis can be confirmed if you have certain autoantibodies in your blood or a substance called ketones in your urine.

Diagnostic tests for gestational diabetes 

Your doctor will order blood tests to check for gestational diabetes at the end of your second trimester or the very beginning of your third trimester, between the 24th and 28th week of pregnancy. If you have certain risk factors for diabetes, your doctor may test you sooner.

The two tests commonly used to check for gestational diabetes are a glucose challenge test and an oral glucose tolerance test. 

Glucose challenge test

In the glucose challenge test, you will drink a sugary solution. After one hour, you’ll undergo a blood draw. If your blood sugar is 140mg/dL or higher, your doctor may order an oral glucose tolerance test to confirm a gestational diabetes diagnosis.

Oral glucose tolerance test 

If your doctor orders an oral glucose tolerance test, you will need to fast beforehand. This test has several steps to it. 

First, a healthcare professional will draw your blood. Next, you will drink a sugary solution. Then, you’ll have your blood drawn every hour for two hours.

In the past, an oral glucose tolerance test was often ordered after a glucose challenge test. Under newer guidelines, your doctor may only order an oral glucose tolerance test.

Why should I take a diabetes test?

Your doctor may recommend a medical test to check for type 1 or type 2 diabetes if you have a family history of the disease or if you exhibit any of the following symptoms:

• Excessive thirst (polydipsia)

• Increased urination (polyuria)

• Fatigue

• Blurred vision

• Frequent infections

• Unexplained weight loss

• Extreme hunger

• Sores that don’t heal quickly

If you do have diabetes, it’s important to start treatment as soon as possible. Uncontrolled blood sugar levels can lead to complications such as kidney damage, cardiovascular disease, nerve damage, vision problems, and foot damage. 

In the US, pregnant women are routinely tested for gestational diabetes. Uncontrolled blood sugar levels can lead to complications for both you and your baby, such as:

• An extra-large baby, which may increase the need for a C-section

• High blood pressure

• The baby could be born with low blood sugar (hypoglycemia)

If you have gestational diabetes during pregnancy, you have a greater risk of developing type 2 diabetes later on. Talk with your doctor about routine medical testing to check your blood sugar levels after your baby is born.  

If you are diagnosed with diabetes, it’s important to follow your doctor’s instructions for home testing. Monitoring your blood sugar levels is crucial to your diabetes treatment plan.

Tips on how to prepare for a diabetes test

If your doctor orders a medical test for diabetes, ask them beforehand what you need to do to prepare. You may keep these questions in mind:

• Do I need to fast before my diabetes test? If so, how many hours?

• Should I follow my normal schedule for medication?

• How long will the test take?

• Will I know the test results right away?

Be sure to follow up with your doctor after a diabetes test.

What should I do if I am diagnosed with diabetes?

You may feel overwhelmed if you learn that you have diabetes. While it is a serious condition, it can be managed.

You have a good chance of controlling your blood sugar levels if you follow your doctor’s treatment plan. Follow your doctor’s orders for home testing and medical testing. 

The lowdown

Diabetes mellitus, often referred to as just diabetes, is a condition that affects how your body produces and uses insulin. Diabetes mellitus should not be confused with a separate, rare condition called diabetes insipidus. 

There are three types of diabetes: type 1, type 2, and gestational. Type 1 diabetes is an autoimmune disorder that some people are genetically predisposed to. Type 2 diabetes can also involve genetic factors, but the condition can be brought on by lifestyle factors such as being overweight and eating a poor diet. Gestational diabetes occurs in women who did not have diabetes prior to their pregnancy.

There are home tests and medical tests for diabetes. Home tests are used by people who have been diagnosed and need to monitor their blood sugar levels. Doctors order medical tests to confirm a diabetes diagnosis. Medical tests can also be used to monitor patients with diabetes. 

As with any other health condition, an early diagnosis of diabetes is important because uncontrolled blood sugar levels can lead to serious complications.