Prediabetes Screening: Testing and Next Steps

Prediabetes is associated with elevated blood sugar levels that are not yet high enough to meet a diagnosis of type 2 diabetes. Besides serving as a stepping stone to diabetes, prediabetes increases a person's chances of developing permanent damage to organs like their kidneys, heart, and eyes.

Screening for prediabetes is essential because detecting the condition early increases your chances of preventing the onset of diabetes and its related complications. This article will review the criteria for when an individual should screen for prediabetes. It will also discuss the three blood test options for detecting prediabetes.

Person talking to healthcare provider about prediabetes screening

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Who Should Get Screened?

The American Diabetes Association (ADA) recommends screening for prediabetes in adults who have a body mass index (BMI) greater than or equal to 25 and exhibit one or more other risk factors.

What Is Body Mass Index?

Body mass index is an approximation of body fat based on a person's height and weight. BMI is a dated, biased measure that doesn’t account for several factors, such as body composition, ethnicity, race, gender, and age. Despite its flaws, BMI is still in widespread use today in the medical community because it is an inexpensive and quick method for analyzing potential health stats and outcomes.

Risk factors for prediabetes include:

  • Having a first-degree relative (e.g., a parent, child, or sibling) with diabetes
  • Belonging to a racial or ethnic group that has a high prevalence of type 2 diabetes (e.g., Black, Latino, Native American, Asian American, or Pacific Islander)
  • Living a sedentary lifestyle

Other risk factors include having a history of certain medical conditions, including:

According to the ADA, screening for prediabetes is also recommended for adults with HIV or gestational diabetes (a form of diabetes that starts during pregnancy).

Additionally, children who meet the following criteria should get screened:

  • Those who are at least 10 years old or have entered puberty
  • Those who are overweight or have obesity
  • Those have at least one other risk factor for type 2 diabetes

What if I Have No Risk Factors?

In individuals without risk factors for prediabetes, the ADA recommends screening begin at age 35.


Prediabetes has a genetic component, which explains why having a parent or sibling with diabetes is considered a risk factor.

Researchers have discovered at least 70 genes believed to be involved in the manifestation of type 2 diabetes. It's thought that mutations (changes in DNA) in these genes can lead to prediabetes by interfering with the production or function of insulin.

What Is Insulin?

Insulin is a hormone made by your pancreas that helps transfer sugar into your cells, where it's converted into energy.

Lifestyle Risk Factors

In addition to the genetic component, unhealthy lifestyle factors also contribute significantly to the development of prediabetes.

These lifestyle factors include:

  • Excess weight
  • Diets high in red and processed meats, high-fat dairy, sugary drinks and snacks, and fast foods
  • Physical inactivity
  • Cigarette smoking


Regardless of your risk, getting tested for prediabetes is crucial if you are experiencing possible symptoms or signs of elevated blood sugar levels.

Some prediabetes symptoms include:

Downsides of Not Screening for Prediabetes

Left undetected (and unmanaged), prediabetes can progress into type 2 diabetes and cause serious health complications. Some of these complications include:

A1C Test

The A1C test, also called the hemoglobin A1C test, is one option for identifying prediabetes. This simple blood test measures the average amount of glucose stuck to hemoglobin A for the past three months.

What Is Hemoglobin A?

Hemoglobin A is a protein in your red blood cells that carries oxygen. Red blood cells live for an average of 120 days, so glucose gradually accumulates on the hemoglobin for around three months.


There is no special preparation for an A1C test. You do not need to fast.


The A1C test is a blood test performed in a laboratory or your healthcare provider's office. It usually involves taking a blood sample from a vein in your arm with a needle. Sometimes, the test is measured with a fingerstick, although the results for that are not as accurate.

If the blood comes from a vein, you will have to take the following steps:

  • Your technician or healthcare provider will ask you to sit in a chair and place your arm on an armrest.
  • They will then identify a vein and clean the area with an alcohol wipe.
  • They will then tie a large rubber band (tourniquet) around your upper arm to help fill the vein with blood.
  • They will then place a small needle into your vein. You may feel a brief sting.
  • Blood will flow through the needle into an attached tube labeled with your name and date of birth.
  • They will then remove the band, followed by the needle.
  • They will then apply gentle pressure followed by an adhesive bandage on the area where they drew the blood.
  • They will then send the blood sample to a laboratory for testing.

If they perform the test via a finger prick, you will take the following steps instead:

  • You will wash and dry your hands.
  • The technician will make a small prick into your fingertip with a tiny, pointed lancet device.
  • A small amount of blood (a drop or two) will flow into a tube or onto a specially designed test strip.
  • The blood sample will go off to a laboratory for testing.


If your A1C level is between 5.7% and 6.4%, your healthcare provider may diagnose prediabetes.

Fasting Plasma Glucose Test

The fasting plasma glucose (FPG) test is a one-step blood test, similar to the A1C test. It measures your blood sugar level when it should be at its lowest.


Before this test, you will have to refrain from eating or drinking anything (except water) for at least eight hours.


The FPG test takes place in a laboratory or your healthcare provider's office. Like the A1C test, the blood sample is obtained through a needle in a vein in your arm or via a finger prick.


If your FPG level is from 100 to 125 milligrams per deciliter (mg/dL), it indicates prediabetes.

Oral Glucose Tolerance Test

The oral glucose tolerance test (OGTT) is a two-step blood test that measures how your body processes glucose in a fasting and non-fasting state. The OGTT involves checking your blood sugar levels before and two hours after drinking a sugary beverage.


Before this test, you will have to abstain from eating or drinking anything except water for at least eight hours.


The OGTT test takes place in a laboratory or in your healthcare provider's office. The blood samples are obtained through a needle in a vein in your arm or, less commonly, via a finger prick.

As a two-step blood test, you can expect the following:

  • The technician or healthcare provider will obtain an initial blood sample.
  • Afterward (and if you are an adult), you will receive a sweet 8-ounce solution to drink containing 75 grams of sugar. Also of note: The dose of sugar for children is based on their weight.
  • After drinking the solution, you will wait in the reception area for two hours.
  • When two hours are up, they will obtain from you a second blood sample.


Glucose levels between 140 mg/dL and 199 mg/dL indicate prediabetes.

Next Steps

Your healthcare provider will recommend intensive lifestyle changes if you test positive for prediabetes.

These lifestyle changes typically include:

  • Losing weight if you are overweight or obese
  • Eating a high-fiber diet rich in vegetables, fruits, and whole grains
  • Engaging in at least 150 minutes of regular physical activity per week
  • Avoiding smoking

In addition to adopting healthy lifestyle habits, your provider may start you on Glucophage (metformin), a prescription medication that helps prevent or delay the development of type 2 diabetes.

Metformin lowers blood sugar levels by decreasing the gut absorption and liver production of glucose. It also improves your cells' sensitivity to insulin.

Healthcare Referrals

If you are diagnosed with prediabetes, your healthcare provider may refer you to a dietitian or physical therapist. These specialists can help you formulate a safe and sustainable plan for achieving lifestyle goals.


Prediabetes is a disease of high blood sugar levels. If left untreated, it can progress to type 2 diabetes and other serious conditions like kidney or heart disease. Unfortunately, many people with prediabetes do not have symptoms, which is why screening is essential.

The American Diabetes Association has set forth various criteria for getting screened. These criteria consider factors like your age, weight, family history, lifestyle, and associated medical conditions. Healthcare providers perform screenings using one of three blood tests—an A1C, fasting plasma glucose, or a two-hour oral glucose tolerance test.

A Word From Verywell

If you or a loved one was recently diagnosed with prediabetes, know that you are not alone. Prediabetes affects 96 million American adults and is projected to affect nearly 366 million individuals worldwide by 2030.

Though prediabetes is a common condition, its diagnosis requires a proactive, take-charge attitude on your part to reverse it. As you care for and work to reverse your prediabetes, be sure to identify unique barriers, stressors, and goals. You may also consider joining a support group, hiring a life coach, or seeing a counselor for further guidance and emotional support.

Frequently Asked Questions

  • Can I test for prediabetes at home?

    Though there are FDA-approved over-the-counter diabetes test kits, they cannot confirm a diagnosis of prediabetes. Be sure to see a healthcare provider if you are experiencing possible symptoms of prediabetes or meet the screening criteria.

  • Do I need to fast for a prediabetes test?

    It depends on which screening test your healthcare provider is using. Two prediabetes screening tests—the fasting plasma glucose test and the oral glucose tolerance test—require that you fast. The A1C test does not require that you fast.

  • How often should I be tested for prediabetes?

    You should be tested for prediabetes every three years. More frequent screening may be required based on your risk factors and test results. If you test positive for prediabetes, your healthcare provider will test you for type 2 diabetes yearly.


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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Colleen Doherty, MD
 Colleen Doherty, MD, is a board-certified internist living with multiple sclerosis.