How to Test for Diabetes & Prediabetes


Florida Medical Clinic Orlando Health

In the United States, diabetes is the 7th leading cause of death, but it’s also one of the most preventable. Early detection helps to reduce the risk of diabetes-related complications such as heart disease, stroke, and limb amputations.

Unfortunately, nearly 1 in 4 Americans living with type diabetes don’t know that they have it, and only 11.6% of those living with prediabetes know. For adults with diabetes, diagnosis is necessary to effectively manage this serious disease – and for those with prediabetes, early diagnosis can significantly reduce their risk of developing diabetes later on.

What is Prediabetes?

Prediabetes means that your blood glucose (blood sugar) levels are higher than average, putting you at an increased risk of developing type 2 diabetes. According to the CDC, more than one-third of Americans have prediabetes, but a staggering 90% don’t know it. It’s understandable, considering prediabetes doesn’t usually cause any noticeable symptoms

The good news is that if you’ve been diagnosed with prediabetes, you can slow or even prevent the onset of type 2 diabetes by making certain lifestyle changes.

Who Should Get Tested for Diabetes?

The American Diabetes Association suggests testing for diabetes every 3 years beginning at age 45. However, your doctor may recommend getting tested earlier or more often if you are at a higher risk of developing diabetes.

Factors that increase your chances of having high blood sugar include:

  • Being overweight or obese
  • Having a family history of diabetes
  • High blood pressure (140/90 mm Hg or higher)
  • High cholesterol
  • Being physically inactive (defined as being active less than 3 times a week)
  • Having PCOS (polycystic ovary syndrome)
  • Having gestational diabetes during pregnancy or having a baby that weighed over 9 lbs

Because people with prediabetes do not typically experience symptoms, it’s especially important to be aware of these risk factors and bring up any concerns you have with your doctor.

Type 2 diabetes, on the other hand, does present a variety of symptoms in the early stages of the disease. These include:

  • Urinating frequently
  • Feeling very thirsty 
  • Feeling very hungry even when you’ve had plenty to eat
  • Slow-healing wounds
  • Tingling or numbness in the hands and feet caused by poor blood circulation
  • Dark, velvety patches of skin (acanthosis nigricans)
  • Extreme fatigue 
  • Blurred vision 

The symptoms above may be present with the onset of type 1 diabetes as well, along with sudden weight loss, fruity-smelling breath, and stupor. But with type 1 diabetes, the need for immediate medical care is often obvious. The early warning signs of type 2 diabetes may not be noticeable for many years after onset. 

If you are at a higher risk of developing type 2 diabetes, don’t wait until you’re experiencing the symptoms above to see a doctor. A chronic condition like diabetes demands a proactive approach to care.

How Does a Doctor Test for Diabetes?

To test for diabetes or prediabetes, your doctor will perform one of 3 tests: the fasting plasma glucose (FPG) test, the A1C test, or a random plasma glucose (RPG) test.

Fasting Plasma Glucose (FPG) Test

The fasting plasma glucose test is the preferred method of testing for type 2 diabetes. As the name suggests, this method of testing requires patients to fast (go without eating or drinking, with the exception of water) for at least 8 hours prior. For this reason, these tests are typically scheduled early in the morning before breakfast.

A normal FPG level is below 100 mg/dl. Prediabetes is defined as an FPG value between 100 mg/dl and 126 mg/dl, and any value higher than 126 mg/dl is diagnostic of diabetes. Keep in mind that your target values may be slightly different.

A1C Test

The A1C is used to test a patient’s average blood glucose levels over the last 3 months. Unlike the fasting plasma glucose test, the A1C is not affected by short-term blood glucose levels and can be taken regardless of the time of a patient’s last meal.

An A1C value below 5.7% is considered normal. Anything between 5.7 and 6.4% percent is diagnostic of prediabetes, while an A1C of 6.5% and above signals diabetes.

While certainly more convenient, bear in mind that the A1C test may be unreliable in certain people – your doctor will be able to determine whether or not you’re a good candidate.

Random Plasma Glucose (RPG) Test

A random plasma glucose test measures the level of glucose (sugar) in your blood at the given time. In this case, “random” simply means that the test can be taken at any time of day without fasting. An RPG test is typically used when a patient is exhibiting serious symptoms of diabetes and needs to be screened immediately.

A random plasma glucose test result above 200 mg/dL, paired with symptoms like extreme thirst, hunger, or fatigue, is indicative of diabetes.

A positive result from any of the above tests is not an automatic diabetes or prediabetes diagnosis – your doctor will perform at least one follow up test to confirm the results.

Can You Test for Diabetes at Home?

People living with diabetes test their blood glucose levels at home all the time, so can’t you do the same?

While the blood glucose testing equipment you can buy over the counter is useful for monitoring diabetes, it is not an effective diagnostic tool. For starters, your ideal blood sugar readings will be different depending on the time of day, your age, or other health conditions. It is in your best interest to get tested by a healthcare professional who can give you an appropriate target range and accurately interpret the results.

So while there is no harm in testing yourself at home, you should take any abnormal results to your doctor for further testing.

Preventing and Managing Diabetes

Understanding how to test for diabetes is the first step to effectively managing or even preventing the onset of the disease altogether.

If your test results in a diagnosis of prediabetes, your doctor will work with you to develop a diet and exercise plan to lower your risk of developing type 2 diabetes. Studies have found that losing just 5% to 10% of your body mass can lower your risk by as much as 58%.

Likewise, testing and diagnosing diabetes early is also beneficial. As an internist, a doctor who specializes in the internal organs, Dr. Shaily Shah understands that diabetes is complex, and there is often overlap between diabetes and other health conditions. Establishing a patient-doctor relationship early on makes it easier for healthcare professionals to keep an eye on their patient’s body systems and manage their care.

Learn more about diabetes care by scheduling an appointment with a Florida Medical Clinic Orlando Health primary care provider.

Disclaimer: This blog covers general information about health-related subjects, but is not a substitute for professional medical expertise and should not be construed as medical advice.


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