The body uses the hormone insulin, produced by the pancreas, to regulate the amount of glucose, or sugar, circulating in the bloodstream. Insulin acts like a key, unlocking cells to allow glucose to enter and be used for energy. Both prediabetes and diabetes occur when this system of glucose regulation begins to fail, leading to elevated blood sugar levels. The difference between the two conditions is found in the severity and duration of this high blood sugar, reflecting distinct stages of metabolic malfunction.
Defining Prediabetes and Diabetes
Prediabetes is the stage where the body’s cells start to become resistant to insulin, known as insulin resistance. In this state, the pancreas has to work harder, producing extra insulin to keep blood sugar levels from rising too high. The body is still mostly able to compensate for the resistance, meaning glucose levels are above the normal range but have not yet reached the established threshold for a diabetes diagnosis. Prediabetes acts as a significant warning sign that the system is under stress.
Diabetes, most commonly Type 2 diabetes, represents a chronic state of sustained high blood sugar where the body can no longer compensate for the insulin resistance. This failure happens because the pancreas eventually cannot produce enough insulin to overcome cellular resistance. The resulting high glucose levels define this condition, which is a more advanced metabolic disorder.
Diagnostic Criteria and Testing Thresholds
The objective difference between the two conditions is defined by specific numerical thresholds across three standard blood tests. A diagnosis of prediabetes indicates that test results fall into an intermediate range, while diabetes is diagnosed when those results are significantly higher.
The A1C test measures a person’s average blood sugar over the previous two to three months. A normal result is below 5.7%, while the prediabetes range is between 5.7% and 6.4%. A result of 6.5% or higher on the A1C test is used to diagnose diabetes.
The Fasting Plasma Glucose (FPG) test measures blood sugar after a person has not eaten for at least eight hours. A normal FPG level is below 100 milligrams per deciliter (mg/dL). Prediabetes is defined by an FPG level between 100 and 125 mg/dL, known as impaired fasting glucose. A result of 126 mg/dL or higher on this test indicates diabetes.
The Oral Glucose Tolerance Test (OGTT) checks blood sugar two hours after drinking a sugary liquid. A normal result is below 140 mg/dL. A prediabetes diagnosis is given for results between 140 and 199 mg/dL, which is called impaired glucose tolerance. A result of 200 mg/dL or higher two hours after the test is a threshold for diagnosing diabetes.
Distinct Management Strategies
The management strategy for prediabetes focuses on the primary goal of reversal and prevention of progression to diabetes. This approach relies heavily on aggressive lifestyle modifications that can restore insulin sensitivity. These changes include aiming for a modest weight loss of 5% to 7% of body weight and engaging in at least 150 minutes of moderate-intensity physical activity each week. Losing this small amount of weight and increasing activity can reduce the risk of developing Type 2 diabetes by over 50%.
Medication, such as metformin, is sometimes considered for prediabetes patients who are at a particularly high risk, such as those who are under 60 years old or have a high body mass index. However, lifestyle changes remain the first and most effective line of action for prediabetes. The overall focus is to halt the progression of metabolic dysfunction before it becomes a chronic disease.
The management of established diabetes shifts the goal to control and mitigation of damage, as the condition is typically chronic. This strategy incorporates lifestyle changes, but they are coupled with pharmaceutical interventions to lower blood glucose. Treatment often involves daily medication, such as metformin or newer glucose-lowering drugs, to improve insulin action or reduce glucose production in the liver.
For some individuals with diabetes, particularly those whose bodies produce very little or no insulin, insulin therapy is necessary to manage blood sugar levels. The ongoing management of diabetes requires regular monitoring of blood glucose and A1C levels to prevent the long-term systemic damage caused by sustained hyperglycemia. The goal is to sustain blood glucose levels within a target range to minimize the risk of complications.
Comparison of Health Risks and Complications
While prediabetes is a serious health condition, its primary risk is the high likelihood of developing Type 2 diabetes, with up to 70% of people with prediabetes eventually progressing to the full disease. Individuals with prediabetes also face an elevated risk for cardiovascular disease, including heart attack and stroke, even before a diabetes diagnosis is made. This increased risk is often linked to the underlying insulin resistance and associated factors like high blood pressure and abnormal cholesterol levels.
Diabetes, characterized by chronic and higher levels of blood glucose, leads to a much greater range of complications involving damage to the small and large blood vessels. Sustained hyperglycemia causes microvascular damage, which manifests as diabetic retinopathy (eye damage), nephropathy (kidney damage), and neuropathy (nerve damage). The risk of all-cause mortality is significantly higher for people with diabetes than for those with prediabetes.
Macrovascular complications in diabetes involve the larger blood vessels, greatly increasing the risk of severe cardiovascular events, such as heart attack, stroke, and peripheral artery disease. Compared to prediabetes, which increases the risk of chronic kidney disease by a small margin, diabetes carries an approximately threefold higher risk. The severity and scope of complications are far greater in diabetes, affecting nearly every major organ system and significantly impacting quality of life.