Diabetes mellitus, more commonly referred to as diabetes, is an impairment in how your body regulates and processes sugar. It can be diagnosed by blood tests that measure your estimated average blood sugar (glucose) levels. Blood glucose comes from your liver and the food you eat. It’s what fuels your muscles and organs and gives you energy. High blood sugar can be an indication of diabetes or prediabetes. Prediabetes means your blood sugar is elevated—and so is your risk for developing type 2 diabetes. 

The first step to decoding your diabetes test results is to understand the differences between type 1, type 2, prediabetes, and gestational diabetes.

Around 90 to 95 percent of diabetes cases are type 2 diabetes, which often occurs in people over the age of 45—although it’s becoming more common in younger people, including children, due to increasing rates of childhood obesity. 


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Who should be screened for diabetes?

In 2021, the US Preventive Services Task Force updated its recommendations for diabetes screening. New recommendations suggest that anyone aged 35 or older who is overweight or obese should be screened for diabetes at least every two years. Those who are pregnant should be screened for gestational diabetes. Women who have been previously diagnosed with gestational diabetes should be screened every three years. Anyone diagnosed with prediabetes should be screened every year. 

People of any age who have symptoms of diabetes should make an appointment with their doctor right away to be tested for it. 

Symptoms of Diabetes Mellitus may include:

  • Increased thirst
  • Urinating often
  • Feeling very hungry—even if you eat
  • Blurry vision
  • Unexplained weight loss
  • Numbness and tingling in your hands and feet

How do we test for diabetes?

There are four different tests that are used to diagnose diabetes. Your doctor will use one or more of them, alongside your medical history, to determine whether you have diabetes—and if so, what type. 

Hemoglobin A1C

A hemoglobin A1C, also known as A1C or HbA1c, is a simple blood test that measures your average blood sugar levels over the past two or three months. The A1C is one of the most commonly used tests to diagnose diabetes and prediabetes. It’s also used as a diabetes management tool, since an A1c is an estimated average of blood glucose over time. Higher A1C levels are associated with complications of diabetes, which can be very serious.

How the A1C test works

Sugar in your bloodstream attaches to a protein in your red blood cells known as hemoglobin. While everyone has some sugar attached to their hemoglobin, higher numbers indicate higher average blood sugar levels. The A1C test measures the percentage of your red blood cells that have sugar-coated hemoglobin:

  • Below 5.7 percent: Normal
  • 5.7 to 6.4 percent: Prediabetes
  • 6.5 percent or above: Diabetes

Here are some other recommendations regarding A1C:

  • If you’re over 45 and have normal blood sugar, repeat the test every three years.
  • If your results indicate prediabetes, work with your doctor to create a plan to reduce your risk, and retest according to your doctor’s recommendations.
  • If you don’t have any diabetes symptoms but your A1C indicates prediabetes or diabetes, test again on a different day to confirm the results.
  • If you have diabetes symptoms and your A1C confirms the diagnosis, work with your doctor to get started right away on a self-management program, and get the A1C test twice a year or as recommended by your doctor.

The higher your percentage is over the diabetes threshold, the more likely you are to develop complications of type 2 diabetes. If you have had an A1C at 5.7% or above, talk to your doctor about how you can best manage your blood sugar.

A1C for type 2 diabetes management

As a diabetes management tool, the A1C helps you track your blood sugar over time. It shouldn’t replace your blood sugar monitoring at home, which gives you snapshots of your blood sugar levels each day to help you stay on top of it.

For most people with diabetes, the target A1C level is 7 percent or less, although your personal A1C goals will depend on factors like your age and other medical conditions you may have.

Fasting plasma glucose (FPG) test

Also known as the fasting blood sugar test, the FPG test checks your blood sugar levels after you’ve been fasting for at least eight hours. The food you consume is a source of blood sugar, which normally spikes after you eat and then goes back down over the following hours. High blood sugar after hours of fasting is a good indication that you may have prediabetes or diabetes. However, to make a diagnosis, your doctor will need to perform the test again on another day shortly after the first to confirm the results. These are the result ranges for the FPG test:

  • 70 to 99 mg/dL: Normal
  • 100 to 125 mg/dL: You may have prediabetes (confirmed with another FPG test)
  • 126 mg/dL or higher: You may have diabetes (confirmed with another FPG test)

Oral glucose tolerance test (OGTT)

The oral glucose tolerance test determines how well your body moves sugar from the blood to the cells. It’s used to diagnose diabetes in people whose fasting plasma glucose (FPG) test results were high, but not high enough to be diagnosed as diabetes. A high OGTT is an earlier sign of diabetes than a high FPG.

How the OGTT works

The OGTT lasts around three hours and involves several blood draws during that time.

You’ll eat as you normally do in the days before the test, then fast during the eight hours before it. 

The test will start with a blood sample to use as a baseline measurement. Then, you’ll drink a sweet liquid that contains around 75 grams of glucose. Your blood will be taken every 30 to 60 minutes after that to measure how much glucose remains. This range helps your doctor understand how your body uses glucose. The glucose levels in your blood two hours after drinking the liquid are the measurements used to diagnose diabetes:

  • Under 140 mg/dL: Normal
  • 140 to 200 mg/dL: Prediabetes
  • Over 200 mg/dL: Diabetes

This test is often used to screen and diagnose gestational diabetes for a woman who is pregnant. If you are pregnant, talk to your doctor to see if you should be tested.

Random blood sugar test

The random blood sugar test is a way to quickly screen for  diabetes, since it doesn’t require fasting or hours-long monitoring. While a type 2 diabetes diagnosis made with a random blood sugar test may require confirmation with an A1C or OGTT, this test is ideal for a fast diagnosis for people with type 1 diabetes who need insulin quickly. 

There’s no range of results for a random glucose test—if the blood sugar level is 200 mg/dL or higher, a diagnosis of diabetes will be confirmed with a FPG or OGTT. 

What a diagnosis of prediabetes means

If you have prediabetes, also known as “impaired glucose tolerance,” you have a considerable risk for type 2 diabetes, heart disease, and stroke. More than one in three American adults have prediabetes, but 84 percent of them don’t know it. Prediabetes often has no symptoms, but it’s important to make lifestyle changes that will lower your blood sugar and prevent diabetes. 

What a diagnosis of diabetes means—and how Forward can help

If you’ve been diagnosed with type 2 diabetes, lowering your blood sugar can help delay or even prevent complications down the road. Through a diabetes-friendly diet, regular exercise, and medication, if indicated, you can lower your blood sugar and effectively manage it for the long-term. Forward can help. As your primary care provider, Forward helps you control your type 2 diabetes through a variety of programs and resources, including our Weight Management Program, Heart Health Program, and app-based preventive tools. Forward makes it easy for you to take control of your health and lower your disease risks or manage a chronic condition through comprehensive testing, goal-setting, and ongoing monitoring so you can live a healthier, happier life.

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