Symptoms of Glucose Intolerance

Glucose intolerance is an umbrella term for a group of metabolic conditions that result in higher than normal blood glucose levels. This includes diabetes and prediabetes. Glucose intolerance also refers to the conditions of impaired fasting glucose and impaired glucose tolerance that are based on which type of glucose test showed prediabetes.

Although there are no concrete symptoms of glucose intolerance, they mirror the symptoms of prediabetes and diabetes. Some of these symptoms include thirst, fatigue, blurred vision, and frequent urination. It is important to check with your healthcare provider to get the proper treatment and diagnosis.

woman eating food while checking insulin levels

BakiBG / Getty Images

Types of Glucose Intolerance 

When it comes to glucose intolerance, there are various types, including:

  • Impaired fasting glucose
  • Impaired glucose tolerance
  • Intermediate hyperglycemia (also known as prediabetes)
  • Type 2 diabetes

Impaired Fasting Glucose

Impaired fasting glucose is one of the stages of the natural progression of diabetes.

The glucose levels of impaired fasting glucose are above normal and also below the level that would be considered an actual diagnosis of diabetes. Although the numbers are low for a diagnosis of diabetes, patients who have impaired fasting glucose are at a high risk of developing the disease.

There is also an opportunity for prevention. Having a conversation and creating a plan with a healthcare professional will help reduce the risk.

Glucose values for impaired fasting glucose are 100 to 125 mg per dL (5.6 to 6.9 mmol per L).

Impaired Glucose Tolerance

Impaired glucose tolerance is known as an increased risk of developing type 2 diabetes. Many individuals do not have symptoms for a long time.

The diagnosis for impaired glucose tolerance is determined by an oral glucose tolerance test.

There are many patients who do have impaired glucose tolerance and already have diabetes complications by the time they are diagnosed with type 2 diabetes. It is important to share any symptoms that you feel with the healthcare provider to get the proper treatment and/or preventive measures.

Glucose values for impaired glucose tolerance are 140 to 199 mg per dL (7.8 to 11.0 mmol) on the 75-g oral glucose tolerance test.

Intermediate Hyperglycemia (Also Known as Prediabetes)

This encompasses impaired fasting glucose and impaired tolerance.

Prediabetes is known as blood glucose levels that are above normal but not high enough for a diabetes diagnosis.

According to the Centers for Disease Control and Prevention (CDC), one in three Americans have prediabetes, and more than 84% don’t know they have it.

When an individual is at the prediabetic stage, the cells in the body do not properly respond to insulin. Because of this, the pancreas produces more insulin to help the cells respond. When this happens on a consistent basis, the pancreas has a hard time producing insulin and the blood sugar rises.

This is the beginning of prediabetes; if it is not managed or prevented, it can lead to type 2 diabetes.

Type 2 Diabetes

If prediabetes is not managed, it can become a type 2 diabetes diagnosis.

When an individual has type 2 diabetes, the body doesn’t respond properly to insulin. The diagnosis can also lead to a number of other health complications, such as:

  • Kidney disease
  • Vision loss
  • Heart disease

It is important to work with the healthcare provider to learn about prevention in the prediabetic stage. If there is a diagnosis of type 2 diabetes, follow a treatment plan with the healthcare provider to manage it properly.


Glucose intolerance does not have clear symptoms, but some individuals could have the same signs as patients with diabetes. These include:

  • Constant thirst
  • Fatigue
  • Blurred vision
  • Frequent need to urinate
  • Neuropathy
  • Loss of muscle mass

Risk Factors

Glucose intolerance is often asymptomatic, so knowing whether or not you have risk factors is important to reach an early diagnosis. The risk factors include:

  • Age
  • Obesity
  • Diet
  • Genetics
  • Lifestyle

A Word From Verywell

If you have symptoms of glucose intolerance, it is important to have a conversation with your healthcare provider. They can help guide you in the right direction and create a proper plan so you can manage your condition and have a healthy outcome.  

Frequently Asked Questions

  • What is glucose intolerance?

    Glucose intolerance is a term used to describe metabolic conditions that result in higher than normal blood sugar levels. Conditions that fall under the umbrella of glucose intolerance include type 2 diabetes, prediabetes, impaired fasting glucose (IFG), and impaired glucose tolerance (IGT).

  • What causes glucose intolerance?

    The exact cause of glucose intolerance is unclear, but there are a few things that can increase your risk for it. Some risk factors are within your control to change, such as eating a well-balanced diet, getting regular exercise, and managing your weight. Other risk factors are nonmodifiable. These include age and having a family history of diabetes or prediabetes. 

  • Can glucose intolerance be reversed?

    Possibly, depending on how far along glucose intolerance has progressed. Impaired fasting glucose, impaired glucose tolerance, and prediabetes-related glucose intolerance may be helped with lifestyle changes, including diet and exercise.

    Some people with type 2 diabetes are able to maintain healthy blood sugar levels without medication through diet and exercise. However, a return to the standard American diet will cause their blood sugar to rise again.

6 Sources
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.
  1. American Diabetes Association. Understanding A1C: diagnosis.

  2. Di Bonito P, Pacifico L, Chiesa C, et al. Impaired fasting glucose and impaired glucose tolerance in children and adolescents with overweight/obesityJ Endocrinol Invest. 2017;40(4):409-416. doi:10.1007/s40618-016-0576-8

  3. Rao SS, Disraeli P, McGregor T. Impaired glucose tolerance and impaired fasting glucoseAm Fam Physician.

  4. Andersson S, Ekman I, Lindblad U, Friberg F. Perceived symptoms in people living with impaired glucose tolerance. Nurs Res Pract. 2011;2011:1-9. doi:10.1155/2011/937038

  5. Centers for Disease Control. Prediabetes. your chance to prevent type 2 diabetes.

  6. American Heart Association. Prediabetes modifiable risk factors.

By Yvelette Stines
Yvelette Stines, MS, MEd, is an author, writer, and communications specialist specializing in health and wellness.