Diagnosing Diabetes

Diabetes and prediabetes screening tests

/ Author:  / Reviewed by: Robert Carlson, M.D

Are you overweight? Do you have a parent or sibling with diabetes? Do you have high blood pressure? If you answered yes to any of these questions, it is time to get tested for diabetes.

About 25 million Americans, or eight percent of the U.S. population, are affected by diabetes. Unfortunately, a good portion of these people do not know they have the condition. This may be because they often have no symptoms.

Luckily, there are simple tests that let you know if you have diabetes or prediabetes. Getting tested is the first step in preventing and controlling your condition.

Who should be tested for diabetes?

Diabetes can be a sneaky disease. That is, you could have diabetes without even knowing it.

For this reason, the American Diabetes Association (ADA) recommends that people be screened for diabetes if they are overweight or obese and have at least one other risk factor for diabetes. You can find out if you are overweight or obese using the body mass index (BMI). A BMI of 25 to 29.9 is considered overweight. A BMI of 30 or more is obese.

If you do not have these risks, the ADA suggests you start getting tested at age 45 every three years.

People under the age of 45 should get tested if they are overweight or obese and have one of the following risk factors:

  • having a parent or sibling with diabetes
  • having high blood pressure
  • having low levels of HDL, or "good," cholesterol
  • having high triglyceride levels
  • having an ethnic background in high-risk groups such as African American, Alaska Native, American Indian, Asian American, Latino, or Pacific Islander
  • giving birth to a baby that weighs more than nine pounds
  • being diagnosed with gestational diabetes (diabetes during pregnancy)
  • having polycystic ovary syndrome
  • having a history of heart disease or diseases that affect the heart and blood vessels
  • having acanthosis nigricans, a condition that causes a dark rash around the neck and armpits

What tests are used to diagnose diabetes?

There are several tests your doctor may use to screen you for diabetes. These include the A1C test, fasting plasma glucose test, random plasma glucose test, and oral glucose tolerance test.

All of these tests measure your blood sugar levels. High blood sugar levels are characteristic of diabetes and can be dangerous.

Glycated hemoglobin (A1C) test

The A1C test shows you your average blood sugar level from the last few months. It measures the percentage of blood sugar attached to hemoglobin, the protein that carries oxygen in red blood cells.

While the A1C test is used in diagnosis, it is more commonly used by those who are already diagnosed with diabetes. It can give patients an accurate picture of their blood sugar control.

Fasting plasma glucose test

The fasting plasma glucose test, or fasting blood sugar test, is one of the most common tools for diagnosing diabetes because it is both cheap and easy to perform.

The test measures blood sugar in a person who has not eaten for at least eight hours.

A fasting blood sugar level of 100 to 125 mg/dL means you have impaired fasting glucose, a type of prediabetes that raises your risk of type 2 diabetes. People with a fasting blood sugar of 126 mg/dL or more have diabetes.

While the fasting blood sugar test can spot diabetes in many people, it has been known to miss certain cases. Fortunately, the oral glucose tolerance test can detect diabetes where the fasting blood sugar test missed it.

Oral glucose tolerance test

The oral glucose tolerance test is known to be more sensitive than the fasting blood sugar test. However, it is less easy to perform.

Patients must fast for eight hours or more before undergoing the oral glucose tolerance test. Blood sugar levels are measured just before and two hours after the patient drinks a beverage containing glucose (a form of sugar).

People are diagnosed with a form of prediabetes called impaired glucose tolerance if their blood sugar is between 140 and 1999 mg/dL two hours after drinking the glucose beverage. A blood sugar level of 200 mg/dL or more indicates diabetes.

Random plasma glucose test

The random, or casual, plasma glucose test is used to diagnose diabetes but not prediabetes. It measures blood sugar levels without taking into account when patients last ate. A doctor will look at the results of this test, along with an assessment of other symptoms, to diagnose diabetes.

You may have diabetes if you have a random blood sugar level of 200 mg/dL or more and the following symptoms:

  • increased urination
  • increased thirst
  • increase hunger
  • unexplained weight loss
  • fatigue
  • blurred vision
  • sores that do not heal

If a doctor uses the random plasma glucose test to screen you for diabetes, he or she is likely to confirm the diagnosis using the fasting plasma glucose test or the oral glucose tolerance test.

What steps are taken after a prediabetes diagnosis?

So, your doctor has run one or more diabetes diagnostic tests on you. The results show that you are at risk of developing type 2 diabetes, or that you have prediabetes. What do you do now?

Study after study has shown that losing body weight through diet and exercise can reduce your risk of diabetes. Shedding just a few pounds can lower your risk significantly. All it takes is a low-fat, low-calorie diet and regular exercise for about 30 minutes, five times per week.

What steps are taken after a diabetes diagnosis?

If you are diagnosed with diabetes, you and your doctor will develop a treatment plan designed to work for you.

The goal of diabetes treatment is to keep blood sugar levels as close to normal as possible. This is done through meal planning, physical activity, and, in many cases, medication.

Weight loss is also key to treating diabetes. As with managing prediabetes, even the slightest amount of weight loss can make a difference.

For most patients, a healthy diet and exercise is all that is needed to lose weight. In extreme cases, however, a doctor may recommend surgery.

A series of recent studies has shown that bariatric surgery, or weight-loss surgery, is more effective than drug treatment for obese individuals with type 2 diabetes.

It is important to keep in mind, though, that surgery is a kind of worst-case-scenario treatment. The hope is that diet and physical activity will control the condition.

Get tested!

If you have any risk factors for diabetes, or you are over the age of 45, you should get tested for diabetes.

It may be scary to think about a diabetes diagnosis, but, as the saying goes, it is better to know than to not know. Getting screened is the first step in preventing, delaying, or treating diabetes.

Talk to your doctor about getting tested today!  

Reviewed by: 
Review Date: 
April 22, 2012