Glucose intolerance is a metabolic condition that reflects the body’s reduced ability to process glucose efficiently, leading to higher-than-normal levels of glucose circulating in the bloodstream (dysglycemia). This state indicates that the mechanisms regulating blood sugar are beginning to fail. While not a disease itself, glucose intolerance is a precursor to more serious conditions, representing an intermediate metabolic stage between normal function and overt diabetes, and indicates a heightened risk for developing Type 2 Diabetes and cardiovascular disease.
Understanding Glucose Intolerance: Definition and Differentiation
Glucose intolerance is characterized by either insulin resistance (cells becoming less responsive to insulin) or the pancreas being unable to produce enough insulin to manage the body’s glucose load. Insulin allows glucose to enter cells for energy; when this process is impaired, glucose builds up in the blood, resulting in hyperglycemia.
This condition is often referred to as pre-diabetes, classified into two categories based on the affected metabolism. Impaired Fasting Glucose (IFG) is diagnosed when blood sugar levels are elevated after fasting, reflecting a problem with the liver’s glucose production. Impaired Glucose Tolerance (IGT) is diagnosed when blood sugar levels are too high two hours after consuming a sugary drink, indicating resistance in muscle and fat cells. Individuals may have IFG, IGT, or both, all representing an increased risk of progressing to Type 2 Diabetes.
Common Physical Signs and Symptoms
Glucose intolerance often presents without noticeable symptoms, especially in the pre-diabetes stage, but signs may appear as blood sugar levels rise. Increased thirst (polydipsia) is common, resulting from the kidneys attempting to flush out excess glucose through urine. This leads to excessive urination (polyuria), which can disrupt sleep and daily life.
Unexplained fatigue or drowsiness is also common, as cells are starved for the glucose they cannot access for energy. High glucose levels can cause blurred vision when fluid shifts into the lens of the eye. Additionally, cuts or sores may take an unusually long time to heal, a complication related to impaired circulation and immune function.
Identifying Glucose Intolerance Through Testing
Medical professionals use specific blood tests to measure the body’s ability to regulate glucose and diagnose glucose intolerance.
Fasting Plasma Glucose (FPG) Test
The FPG test is a common screening tool, requiring fasting for at least eight hours before blood is drawn. A result between 100 and 125 milligrams per deciliter (mg/dL) is considered diagnostic for Impaired Fasting Glucose (IFG).
Oral Glucose Tolerance Test (OGTT)
The OGTT provides a dynamic assessment of how the body handles a glucose load. This test measures blood sugar after an overnight fast, followed by a second measurement two hours after drinking a standard 75-gram glucose solution. A two-hour plasma glucose result between 140 and 199 mg/dL indicates Impaired Glucose Tolerance (IGT).
A1C Test
The A1C test provides a snapshot of average blood glucose levels over the previous two to three months by measuring the percentage of sugar-coated hemoglobin. An A1C result between 5.7% and 6.4% is also used to diagnose glucose intolerance.
Essential Lifestyle Strategies for Management
Managing glucose intolerance and preventing its progression involves lifestyle changes focusing on diet, exercise, and weight management.
Dietary Changes
Dietary intervention focuses on reducing caloric intake and shifting meal composition. Consuming fiber-rich whole grains, fruits, and vegetables helps slow sugar absorption, preventing sharp spikes in blood glucose. Limiting added sugars and unhealthy fats is also important, as these contribute to insulin resistance.
Physical Activity
Regular physical activity significantly improves insulin sensitivity, making cells more receptive to insulin. Guidelines recommend a minimum of 150 minutes of moderate-intensity aerobic exercise weekly, such as brisk walking. Resistance training is also beneficial because muscle tissue is a primary site for glucose uptake, and building muscle mass enhances this process.
Weight Management
Achieving a healthy body weight is effective for reversing glucose intolerance. Losing a modest 5% to 7% of body weight can significantly reduce the risk of developing Type 2 Diabetes. Weight loss decreases fat stored in the liver and muscle, which directly reduces insulin resistance. These combined actions often return blood glucose levels to a normal range.