You may have heard the terms impaired glucose tolerance (IGT) and prediabetes thrown around a lot, but you may not know if they’re interchangeable or completely different conditions.

This article will clear up any misconceptions about IGT and prediabetes, and provide more details on what you should know about being diagnosed with and managing IGT.

IGT means that blood sugar levels are elevated but not elevated enough to warrant a diagnosis of diabetes.

Between 10% and 15% of all U.S. adults have either impaired glucose tolerance or impaired fasting glucose, which is focused on pre-meal glucose levels.

What is a glucose tolerance test?

One of the main ways you diagnose IGT is the glucose tolerance test, a diagnostic lab test to check how your body moves sugar from the blood into tissues like muscle and fat.

How it works:

  1. You have a blood sample taken.
  2. Then you drink a sweet liquid containing about 75 grams (g) of glucose.
  3. Your blood is taken again every 30 to 60 minutes after you drink this liquid, to measure your glucose changes.
  4. Blood is taken 2 hours after you drink the liquid, though sometimes a longer time period of up to 3 hours may be ordered.

If you have IGT, you may see blood sugars between 140 and 199 milligrams per deciliter (mg/dL) after 2 hours on this oral glucose test.

Was this helpful?

Yes, the two terms are often used in place of each other.

Impaired glucose tolerance is also known as borderline diabetes and prediabetes. They all share the same characteristics of elevated blood glucose levels that need to be watched but aren’t quite high enough to constitute a diabetes diagnosis.

People who are diagnosed with impaired glucose tolerance are at a significantly higher risk of developing type 2 diabetes, without interventions.

Most doctors consider blood sugar levels at 200 mg/dL or above a few hours after drinking the glucose drink diabetes, requiring intervention. If your blood sugar falls between 140 and 199 mg/dL at the 2-hour mark, you most likely have impaired glucose tolerance.

If your results are unreliable, your doctor may order another glucose tolerance test for a future date.

While glucose tolerance tests are frequently given to people at risk of prediabetes and type 2 diabetes, they’re also given to pregnant people at the end of their second trimester of pregnancy, between 24 and 28 weeks.

These tests are used to detect gestational diabetes mellitus (GDM), which is a form of diabetes estimated to occur in 2% to 14% of pregnancies in the United States. GDM is the diagnosis of diabetes in people who are pregnant, and the diagnosis is the same.

This condition occurs when the body can’t make enough insulin while pregnant. Doctors will only give this diagnosis to people who don’t already have diabetes. It can only be diagnosed during pregnancy and usually goes away after the person gives birth.

According to the Centers for Disease Control and Prevention (CDC), between 2% and 10% of all pregnancies in the United States each year result in a gestational diabetes diagnosis.

Exercise improves insulin sensitivity and glucose uptake by cells.

For that reason, the CDC recommends that people with impaired glucose tolerance or prediabetes lose 5% to 7% of their body weight and increase physical activity. Those activities may include biking, walking, or swimming 150 minutes per week, or about 30 minutes per day. This should happen most days of the week.

Based on the CDC guidance, someone weighing an average of 250 pounds would need to lose between 12.5 and 17.5 pounds to reverse prediabetes and to no longer have an elevated risk of type 2 diabetes.

While being overweight or having obesity is a risk factor for developing IGT, prediabetes, and type 2 diabetes, it’s important to consult your healthcare team about your individual case and diabetes risk. They can help you develop a plan to help address prediabetes in a way that’s right for you.

Note that the CDC-recognized National Diabetes Prevention Program (NDPP) is an evidence-based program, which is offered in all states and covered by most insurance plans (including Medicare), that can teach the basics of reversing prediabetes.

According to the NDPP, program participants can cut their risk of developing type 2 diabetes by 58% (or 71% for people 60 years and older).

If you have impaired glucose tolerance or prediabetes, it’s best to meet with your doctor or a registered dietitian to create a sustainable eating plan that will work for you.

However, focusing on whole foods that have plenty of fiber, increasing your water intake, and eliminating added sugars from your diet can increase your insulin sensitivity and help you lose weight, which can help with the reversal of IGT and prediabetes.

Some foods that you may want to incorporate into your diet include:

  • plenty of leafy, green vegetables, like kale, spinach, Swiss chard
  • cruciferous vegetables, like cabbage, broccoli, cauliflower, and brussels sprouts
  • lean proteins, such as chicken, fish, tofu, and turkey
  • low fat dairy, like Greek yogurt and milk
  • lower carbohydrate fruits, like berries, avocado, and coconut
  • healthy fats, like extra virgin olive oil, seeds, nuts, and peanut butter
  • beans and legumes, such as chickpeas, lentils, kidney beans, and black beans

If you’ve recently received an impaired glucose tolerance or prediabetes diagnosis, your doctor will want to check your blood sugar (and perhaps run a hemoglobin A1C test) every few months or annually to see if your blood sugar levels are trending higher, which would merit a diabetes diagnosis.

Consult your healthcare team about blood sugar management at home if you have IGT or prediabetes, as well as other risk factors for type 2 diabetes. Those risk factors may include:

  • being over the age of 45
  • having obesity
  • having a family history of type 2 diabetes
  • having gestational diabetes during pregnancy
  • being African American, Hispanic or Latino, American Indian, Pacific Islander, or of Asian descent

At-home finger stick glucose meters are available at most pharmacies over the counter. Checking your blood sugar at home is simple and takes seconds.

If your doctor recommends this, they can write you a prescription for test strips, as a copayment through insurance coverage may be less expensive than buying them at cash prices at a pharmacy.

IGT is a blanket term describing a metabolic condition that causes higher-than-normal blood sugar levels. It may also be referred to as borderline diabetes or prediabetes. Without taking action, people may develop type 2 diabetes.

A glucose tolerance test is a way to diagnose IGT. This is a lab test that may take a few hours, and it involves drinking a sweet liquid to check your glucose levels. If your blood sugar results are between 140 and 199 mg/dL at the 2-hour mark, you most likely have impaired glucose tolerance.

IGT is reversible with diet and exercise. Along with other risk factors for type 2 diabetes, your healthcare team may want to recheck your glucose levels every few months.