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8 Min

What is Glucose Intolerance?

Written by
Team Nutrisense
Reviewed by
Kara Collier
a person eating muffins looking irritated

If you have glucose intolerance, you may be very aware of your blood glucose levels. Or, you may be concerned about your blood glucose levels and mindful of your symptoms, but unsure of how to monitor them.

Keeping track of your blood glucose values and ensuring you have normal glucose tolerance can be difficult, especially when glucose levels fluctuate throughout the day.
Diet, exercise, hormones, sleep patterns, meal timings, medication, and stress all have an impact on your glucose levels.

If you are unsure of how these factors specifically affect you, it might be difficult to maintain optimum blood glucose levels throughout the day. But if you are glucose-intolerant, then it makes this process even more complicated.

A simple and effective way to monitor and manage your blood glucose levels is to use a continuous glucose monitor (CGM). Maintaining optimal blood glucose levels is key to lowering your risk for long-term health issues, managing a healthy weight, and taking care of your body.

We'll give you an overview of glucose intolerance, how it affects your body, and why blood glucose monitoring is vital to blood glucose management.

What is Glucose Intolerance?

a person eating muffins looking irritated

Glucose intolerance is a term that covers several metabolic conditions that cause abnormal blood glucose levels. These conditions include:

  • Impaired fasting glucose (IFG). Also known as impaired fasting glycemia, metabolic syndrome, or prediabetes. This is when blood glucose levels are high during periods of fasting. However, glucose levels are not high enough to be considered diabetic.
  • Impaired glucose tolerance (IGT). This is when your blood glucose levels are higher than normal but not high enough to be diagnosed as diabetic.
  • Prediabetes. The term prediabetes is an umbrella term for both impaired fasting glucose and impaired glucose tolerance. Although commonly used, the World Health Organization (WHO) advises that the term intermediate hyperglycemia is used to avoid stigma, so this is another term that you may see used. Prediabetes will develop into type 2 diabetes in approximately 25% of people within 3–5 years. Up to 70% of people with prediabetes will become diabetic during their lifetime.
  • Type 2 diabetes. This is the most common form of diabetes. It is a disease that occurs when your blood glucose is too high. Specific blood tests are carried out to diagnose type 2 diabetes.

What Causes Glucose Intolerance?

Within the scientific and healthcare community, the cause of glucose intolerance is unknown. However, a family history of diabetes and genetics are considered to play a significant role.

Risk factors that increase the likelihood of becoming glucose intolerant include:

  • Lack of regular exercise
  • Obesity
  • Excess fat around the abdomen
  • High blood pressure
  • High cholesterol levels
  • Dietary choices
  • Age (risk increases over the age of 45)
  • Other pre-existing conditions such as obstructive sleep apnea, gestational diabetes mellitus, and polycystic ovary syndrome)
  • Ethnicity (Black, Hispanic, American Indian, and Asian American people are at higher risk of developing prediabetes)

Symptoms of Glucose Intolerance

Many people with impaired glucose tolerance will not display any symptoms at all.

If glucose intolerance is worsening or developing from impaired glucose intolerance to clinical diabetes, the following symptoms are most commonly described:

  • Excessive thirst
  • Blurry vision
  • Dry mouth
  • Extreme fatigue
  • Increased need to urinate more often
  • Drowsiness
  • Loss of muscle mass

What's The Difference Between Glucose Intolerance and Diabetes?

You do not have to have a diagnosis of diabetes to be glucose intolerant. However, being glucose intolerant increases your risk of developing type 2 diabetes. Blood tests are used to distinguish a diagnosis between glucose intolerance and diabetes (see below).

What's The Difference Between Glucose Intolerance and Insulin Resistance?

Insulin resistance is when cells in your muscles, fat, and liver are less effective at removing glucose from your blood. To help get glucose into these cells and lower your blood glucose levels, the pancreas makes more insulin. This pancreatic response leads to high insulin levels in your blood and is called insulin resistance.

If your pancreas produces enough insulin, your blood glucose levels will stay in the healthy range or normal glucose tolerance. However, if there is not enough insulin, the extra glucose stays in your bloodstream instead of entering your cells. Over time, your cells may become more resistant to insulin. This can lead to a rise in both insulin and blood glucose levels. If blood glucose levels rise, this is known as glucose intolerance.


What is a Glucose Intolerance Test?

There are three types of glucose intolerance tests. They are all blood tests.

1) Fasting plasma glucose. This is a blood test taken after an eight hour overnight fast to measure blood glucose levels.

2) Oral glucose tolerance test (OGTT). This type of blood glucose test is done over several stages. First, a blood sample is taken, and fasting blood glucose levels are analyzed. Secondly, you are given a syrupy glucose solution to drink. Finally, a healthcare practitioner will measure your blood glucose levels again, two hours after drinking the solution.

3) Glycated hemoglobin. This blood test gives an average of your blood glucose levels over two to three months.

The results from these blood tests are shown in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). The recommended blood glucose levels for diagnosing diabetes and intermediate hyperglycemia (prediabetes) by the WHO are as follows:

Impaired Fasting Glucose

  • Fasting plasma glucose 6.1 to 6.9mmol/l (110mg/dl to 125mg/dl)
  • Oral glucose tolerance test <7.8mmol/l (140mg/dl) (if measured)

Impaired Glucose Intolerance

  • Fasting plasma glucose <7.0mmol/l (126mg/dl)
  • Oral glucose tolerance test ≥7.8 and <11.1mmol/l (140mg/dl and 200mg/dl)

Type 2 Diabetes

  • Fasting plasma glucose ≥7.0mmol/l (126mg/dl)
  • Oral glucose tolerance test ≥11.1mmol/l (200mg/dl)

Is There a Treatment For Glucose Intolerance?

The treatment for glucose intolerance may differ depending on if you have been diagnosed with IFG, IGT, or type 2 diabetes. Treatment includes lifestyle interventions, but in some cases, medication may be prescribed.

The following lifestyle modifications are recommended:

  • Eat a healthy diet. Food such as red meats and sugar-sweetened drinks are associated with an increased risk of type 2 diabetes. In comparison, increasing the amount of nuts, berries, yogurt, and high fiber carbohydrates have been shown to reduce the risk of diabetes.
  • Increase physical activity. The CDC shows that exercise helps control your blood sugar levels. It also lowers your risk of heart disease and nerve damage.
  • Maintain a healthy BMI. Body mass index is a measure of body fat based on height and weight that applies to adult men and women. According to the American Diabetes Association, being overweight not only raises your risk for type 2 diabetes but also of heart disease and stroke. Even a small amount of weight loss can make a big difference.
  • Reduce alcohol intake. Binge drinking and large quantities of alcohol can be harmful. Too much alcohol may cause pancreatitis, which impairs the ability of the pancreas to secrete insulin. This, in turn, can potentially lead to diabetes.
  • Stop smoking. The Food and Drug Administration (FDA) reports that smokers are 30-40% more likely to develop type 2 diabetes than nonsmokers.

Medication may be prescribed to help lower blood sugar levels. The most common medication prescribed is Metformin. Your doctor might also advise medication to control cholesterol or high blood pressure if these are additional problems that you have.

How Can I Reduce my Glucose Intolerance?

One of the most effective ways to reduce glucose intolerance is by using a CGM to understand and monitor your glucose levels. This will give you the data that you need to naturally lower your blood glucose levels.

Your body is unique and may respond differently to certain foods. Therefore, there is no way of knowing how each type of food impacts your glucose levels unless you are wearing a CGM and can observe what happens to your glucose levels in real-time.

A CGM shows you how your glucose levels react to diet, exercise, medication, sleep, and stress. This allows you to develop a truly personalized nutrition plan and modify your lifestyle to reach optimal health.

Wearing a CGM will give you an assessment of your overall metabolic health and help you identify conditions such as insulin resistance and insulin sensitivity. Once you develop an understanding of how your blood glucose levels react to your diet and lifestyle, you can alter your nutrition and daily habits until everything is performing optimally.

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